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During the final thirty years of his life, after changing the course of modern physics, Albert Einstein sought a unified physics theory relentlessly. He pursued an approach to describe nature's forces within a single, all-encompassing, coherent framework. A passionate belief drove Einstein that the most profound understanding of the Universe would reveal its most real wonder: the simplicity and power of the principles. Einstein wanted to illustrate the Universe's workings with a clearness never before achieved. Einstein never achieved this dream of a single unified theory. But in later years, physicists have built steadily on the discoveries of predecessors for a fuller understanding of how the Universe works. Long after Einstein and his quest for a unified theory, physicists believe they have finally found a framework for stitching many insights together into a seamless framework capable of describing all physical phenomena. Simply put, string theory is a mathematical framework that encompasses all the forces of nature in a single unified theory. "Everything should be made as simple as possible, but not simpler". -Albert Einstein String theory aims to be the "theory of everything" — that is, the single physical theory that describes all physical reality at the most fundamental level. If the idea is successful, it could demonstrate many of the fundamental questions about our Universe. Why string theory? String theory is the most likely contender for a successful theory of quantum gravity that hopes to unite two major physical laws of the Universe into one unified framework. Quantum physics and general relativity don't work together to understand and represent two different types of behaviour in totally different ways. We will get into more details on this phenomenon later. Studying string theory's implications means understanding profound aspects of our reality at the most fundamental levels. What is string theory? According to String theory, the Universe is composed of vibrating filaments of energy rather than minuscule particles of matter. These vibrating strings of energy represent the most fundamental aspect of nature. String theory proclaims that the observed properties of a particle, like a proton, electron or neutron, result from the various ways in which a string can vibrate. All matter in our Universe is made of the vibrations of these strings. According to string theory, the force that acts on all matter particles are also associated with particular patterns of string vibration. String theory and its unifying nature: Modern physics has two basic scientific laws generally accepted by most scientists: quantum mechanics and general relativity. These scientific laws describe radically dissimilar fields of study. Quantum physics breakdowns the smallest fundamental building blocks of matter, while relativity describes nature at the scale of planets, stars, galaxies, and the entire Universe. String theory attempts to unify quantum mechanics and general relativity by unifying the four fundamental forces in the Universe — the electromagnetic force, the strong nuclear force, the weak nuclear force, and gravity. These elemental forces appear as different and distinct phenomena. String theorists believe these forces can be described by strings interacting within a single mathematical framework. The fundamental implications of String Theory; ✓ According to String theory, all objects in our Universe are composed of vibrating filaments of energy, not point-like particles of matter. ✓ String theory attempts to combine general relativity (gravity) with quantum physics and unify all the fundamental forces of the Universe. ✓ String theory predicts a new connection (called supersymmetry ) between two fundamentally different types of particles, bosons and fermions. ✓ String theory predicts several extra (usually unobservable) dimensions to the Universe. ✓ String theory describes 10^500 separate universes (a multiverse), with different constants of nature and even different laws of physics. ✓ Instantly after the Big Bang, the Universe is believed to have expanded quite rapidly through a process called "inflation". But the string theory has trouble producing inflation in its equations. ✓ One of string theory's most dramatic predictions is that we should find cosmic strings. These would be billions of light-years long, thinner than a proton and spectacularly dense. As they could reveal themselves in images of distant galaxies Though String theory offers a multitude of complex solutions for the Universe's tricky riddles, it lacks experimental analysis and many other drawbacks. As long as the search for the Ultimate truth behind the Universe remains, scientists believe string theory might hold its ground and provide potential answers to the great questions. In upcoming posts, we shall deal with the multiverse concept, extra dimensions, cosmic strings, and the weird awesomeness string theory holds.

A beginner's guide to string theory

During the final thirty years of his life, after changing the course of modern physics, Albert Einstein sought a unified physics theory...

4 Feb 2022
In our day to day commuting, we travel in 2D paths and navigate using landmarks. But in space, your navigation happens in 3D, and there aren’t close landmarks because space is vast and mostly empty. When talking about space drives, we will need a highly reliable navigation system. In this article, we will explore using pulsars for space navigation. When a massive star dies, it either forms a neutron star or a black hole. A pulsar is a neutron star with light beams at both its poles. You can think of it as a lighthouse and every time the beam passes through our line of sight we see a signal. Since pulsars rotate rapidly with great stability and precision close to that of atomic clocks in long time scales, they are an excellent candidate for a ‘Galactic Positioning System’. Let’s first understand how regular GPS works. A Global Positioning System needs a minimum of 4 satellite signals that transmit radio signals and a receiver that has a model of the signals without delay. Using the delay between the signals and their direction, we calculate the location of the receiver. In space, radio waves aren’t reliable because of ‘dispersion’ due to dust. We have a solution for that - replace satellites with pulsars that emit in X-rays! We have timing models for pulsars that can predict the arrival time of pulses at any point in space. The Neutron Star Interior Composition Explorer (NICER) instrument aboard the International Space Station (ISS) conducted the first demonstrations of the concept of X-ray Navigation (XNAV) achieving lower than 1 km error. Recently, using data from NICER, astronomers have created pulsar surface-emission models that challenge our standard bipolar lighthouse model. Developing our understanding of pulsar emission and changes that occur in the ‘steady’ signals because of physical reasons like starquakes can help us better our timing models for pulsar signals. Along with improved X-ray instruments, Pulsars have the potential to be the cosmic lighthouses for our future space sailors

Learn how Pulsars are used for navigation in space

In our day to day commuting, we travel in 2D paths and navigate using landmarks. But in space, your navigation happens in 3D, and there...

11 Mar 2021
In 1995, astronomers found the first-ever planet orbiting another main-sequence star. It was 51 Pegasi, and it was nothing like astronomers had ever envisioned. It was almost the mass of Jupiter but orbited its star every four days. Even Mercury, the smallest planet in our Solar System, needs 88 days to around the Sun. But four days? It seemed almost impossible. As astronomers continued their hunt, more and more of these massive planets orbiting so close to their stars kept popping up, and they named them Hot Jupiters. We now know of hundreds of these hot Jupiters. And it turns out that about 1.2% of stars have hot Jupiters orbiting around them. It seems absurd, and we have two problems with these types of planets. One, they shouldn't exist. Two, they shouldn't exist at the places we see them! What is planetary migration? Our old planetary formation models say that you are supposed to see rocky worlds of terrestrial planets close to the star, gas planets in between, and ice worlds farther out. Gas giants like Jupiter can't form close to their star; the heat would make all the volatile gasses evaporate. The radiational eruptions from a newly forming star should have wiped out any excess matter from the internal orbits, stopping planets' formation. The only way out of this mess is if the planets developed farther out and moved to their current positions, resulting from planetary migration. Planetary migration happens when a planet interacts with a disk of gas or planetesimals or any other body in the star system, resulting in modifying its orbit around the star. The most popular theory about planetary migration is the Nice model. An international group of scientists drafted a series of papers explaining the Solar System's arrangement as we see it today. According to the paper, billions of years ago, only the giant planets - Jupiter, Saturn, Uranus, and Neptune clustered together into a much more compact formation around the Sun in perfectly circular orbits. Presently the planets don't follow circular orbits; they're more elliptical, orbiting with a much more significant gap between them. Uranus seems to be rotating sideways. Neptune's Moon that orbits in the reverse direction to every other large Moon in the Solar System. It's complete chaos! What could have possibly happened to create such a dramatic change? Scientists account for these changes through Planetary migration. Simulation showing the outer planets and the Kuiper belt: a) Before Jupiter–Saturn 2:1 resonance. b) Scattering of Kuiper belt objects into the Solar System after the orbital shift of Neptune. c) After ejection of Kuiper belt bodies by Jupiter. Planets are shown: Jupiter (green circle), Saturn (orange circle), Uranus (light blue circle), and Neptune (dark blue circle). Simulation created using data from the Nice Model Types of planetary migration: There are three kinds of migration that can occur in a planetary system. Type I is gas-driven. In the early stages of any planetary system, the primordial planets orbit the star along with a disk of gas and dust. As they travel around, the gas stacks up into higher density regions; in these regions' gravity causes a planet to gain or lose angular momentum, pushing it closer or farther from its star. If the planet loses angular momentum, it gets drawn outwards, and if it gains angular momentum, it is drawn inwards. Larger planets like Jupiter clear out these regions pretty quickly, which leads us to Type II, which happens after a planet has wiped out the disk. Now the mass of the planet itself pulls the gas around it into the open gap in the disk. The pushing and pulling effects cause the planet to lose momentum, making it migrate inward; thus, planets like hot Jupiters can get close to their stars. This process gets out of control, leading to Type III migration, where other material like gases enters the gap, causing an inward migration. In just a few orbits, the planet gets pulled significantly inward. Our Solar System chose the path of violence when it comes to migration. Planets and planetesimals smashed into each other, threw things out of orbit, and planets switched positions. Yet, planetary migration played a pivotal role in forming the solar systems we see today. The Grand tack hypothesis: The grand tack hypothesis is an extension of the Nice model that explains the size of Mars and the asteroid belt. According to this hypothesis, Jupiter migrated inwards up to the current position of Mars and later reversed its location due to Saturn's gravitational pull, ultimately ending up near its current orbit. Jupiter's planetary migration's reversal is almost like a sailboat changing directions (tacking) as it travels against the wind. The planetesimal disk got trimmed by Jupiter's movement, limiting the raw material available to form Mars. Jupiter double-crosses the asteroid belt, scattering asteroids both outward and inward. As a result, the asteroid belt ends up with a reduced mass, disorders, inclinations, irregularities, and materials originating from both inside and outside Jupiter's orbit. The collisions were so intense; it may have pushed an early generation of planets into the Sun. How did everything happen? As we read in the previous article about planets' formation, only the giant planets - Jupiter, Saturn, Uranus, and Neptune formed first. They weren't at their current positions but were grouped in compact, circular orbits formation around the Sun. Small planetesimals surrounded them like an envelope. The innermost planet Jupiter was almost at the current position of Mars, closely followed by the other planets. Planetesimals at the inner edge interacted with the outermost giant planet, which changes these small objects' orbits. As a result, the planets scatter the small icy bodies and push them inwards. These icy bodies' inward movement causes the outermost planet to tug outwards, preserving the angular momentum. This event continues till these planetesimals scatter off the next planet they encounter, successively moving the orbits of Uranus, Neptune, and Saturn outwards. A minute movement can change the orbits of the planets by significant amounts. The process continues until the planetesimals interact with the most massive planet, Jupiter, whose enormous gravity throws them into highly elliptical orbits or even expels them entirely from the Solar System, which in turn causes Jupiter to move slightly inward. After several millions of slow, gradual migration, Jupiter and Saturn attain their 1:2 mean-motion resonance. 1:2 mean motion resonance means for every rotation Jupiter completes, Saturn completes two. It's the perfect gravitational dance. This resonance amplifies their orbital irregularities, destabilizing the whole planetary system. The order of the giant planets changes suddenly, and Jupiter moves Saturn to its current position. This position shift among the gas giants causes gravitational interferences between two ice giants, driving Neptune and Uranus into eccentric orbits. This time it's the ice giants' turn to perpetuate the chaos. Neptune and Uranus then break into the planetesimal disk, entirely scattering it and eliminating 99% of its mass. Some of the planetesimals get thrown into the inner Solar System by these giants like fun confetti, creating unexpected havoc on the terrestrial planets, called the Late Heavy Bombardment. The planets mangling among themselves is not a new thing. They get caught in each other's gravity or tidal forces from the Sun all the time. But all these events shape the star system we see today, and it's the only one we know that bears life. The late heavy bombardment, planetary migration, formation of satellites and ring systems around planets shaped us. They gave way to life on this planet. Stay tuned to learn more about the events that shaped the solar system. .

How to shuffle planets around? - Understanding Planetary migration in the solar system

Planetary migration happens when a planet interacts with a disk of gas or planetesimals or any other body in the star system, resulting in m

5 Mar 2021
Quantum mechanics is a conceptual framework for understanding the microscopic properties of the universe. There is a quote by Niels Bohr, one of the founding figures of quantum mechanics: "Anyone who thinks they can talk about quantum mechanics without getting dizzy hasn't yet understood the first word of it. -Niels Bohr Now, why would that be the case? Why thinking about a fundamental concept make one dizzy? He intends that we are born with a remarkable instinct for classical physics but not quantum mechanics. Classical physics and Quantum Mechanics: Take a ball in your hand, toss it up in the air and try catching it. Most of us can do it; it doesn't require any particular skill set. Humans have evolved to survive; we need specific skills to know where to throw a spear or throw a rock to get the next meal. And consequently, we learned the fundamental physics of the everyday world without thinking much about it. We acquired that intuitively. And that's why when you throw an object, you don't have to through some elaborate calculation to figure out where it is going to land. The classical way of understanding physics belongs in our being, and we witness it every day all around us. But when we investigate the world of the very small, we seem to be clueless. We don't have experience or intuition in that domain. It puts us in a vulnerable position where we must use mathematics, experiment, and observation tools to gaze deeper into reality. And that's what quantum mechanics is all about. It's trying to describe what exactly happens in the micro-world. You might think that why should I learn about some weird subatomic particles that might not affect my life in any way? But think again, we are all nothing but a collection of these particles. Any weirdness we find in the microworld, in some sense, has an impact on the macroworld. There's not even such a sharp divide between the small and the big. The microscopic weirdness we witness in the Quantum realm is inexplicably connected to us. And inadvertently, to understand the big, we need to start from small. In this post, we will step into the Quantum world by deconstructing the classical view of reality. Classical mechanics, as it went deep down into the atoms' scale and the atoms' structure, our understanding just snaps and breaks. We couldn't even find out atoms existed till the 20th century. When we did find out, none of the macroscopic rules applied in the atomic world. It took almost 30 years for Quantum Mechanics to merge into a coherent theory. But by 1928, formulas and rules were already put in place by the most genius of minds. We do make successful and accurate predictions using this conceptual framework, but no one understands what exactly is going on. Light and quanta: The Quantum mechanical puzzle started when physicists tried to understand the nature of light. Before the puzzling properties of light send us down a spiral, we need to understand we need to know what quanta are. The energy that exists in the universe transmits itself through electromagnetic radiation, and light is also a form of electromagnetic radiation. James Clerk Maxwell studied the nature of electromagnetic radiation and light; he ended up putting both of them together. He discovered that self-propagating electromagnetic waves would travel through space at a constant speed, that is, the speed of light. Through this observation, Maxwell concluded that light must also be a form of electromagnetic radiation. In 1873, he published A Treatise on Electricity and Magnetism- a full mathematical description of electric and magnetic fields' behaviour, we call Maxwell's equations. Everyone agreed that light propagates in the form of waves like every other electromagnetic radiation out there. While no one seems to contradict the wave nature of light came Max Plank. He suggested that light appears to propagate as waves, but the energy carried comes in tiny packets or lumps called quanta. It was a remarkable observation, but it was thought to be just an idea. In 1905, Albert Einstein took the idea of light quanta, ran with it, and earned himself a Nobel prize in 1921. Einstein proved the existence of Plank's quanta through his photoelectric effect. The photoelectric effect is when light shines on certain metals; they knock off electrons from the metal, creating electricity. According to Einstein, a beam of light is a stream of tiny photons travelling at a constant speed that kicks out electrons from metals. All these discoveries pose a difficult problem in front of us. Now we have in our hands' substantial experimental evidence that light is a wave but also composed of particles. What is the true nature of light anyway? Is it a particle or a wave? How can a wave be composed of particles? The double-slit experiment and the wave-particle duality: The Double Slit Experiment allows us to get to the heart of the wave-particle duality. This experiment emerged from an accident in the laboratory at Bell Labs. The basic idea is to take a light source and shine that light as a narrow beam on a screen with two gaps in it, and you look at the pattern of light behind the two slots (two slits) on the screen. So the slits are literally gaps in a black sheet of paper. The light's merely passing through them. So simple, right? If the light is a particle, you'd expect a pattern where it has passed through one of the slits, and there is a large gap in between the slits. If the light is a wave, you might expect something different as the light coming through one part of the slit interferes with the light going through the other part of the slit. It would result in what we call an interference pattern. And the weird thing about the quantum two-slit experiment is that it seems, light, in various ways, to be doing both of those things simultaneously. Let's say we carry out the experiment the way we described, but we don't start with photons or electrons; we begin with bullets or something. So what would we expect to happen in this experiment? You have the source of the pellets spitting out the bullets, and some of them go through the holes, and the ones that go through the holes travel straight ahead. And we get precisely two bands at the back, indicating the pellets that went through the right slit, on the right, and the left bar is the pellets that went through the left slit as a result. The result is straightforward, simple, and even dull if we think about it. But if we took the bullets and dialed them down to a tiny subatomic size, we get something absolutely different. This behaviour of particles leaves us with furthermore questions than answers. It is tempting to ask, okay; light behaves in weird manners, so what? But wait, the reality is rather strange than science fiction. Matter particles also behave the same way. Further reading: Two slits and one hell of a quantum conundrum Matter particles are also waves: In 1923, french nobleman Prince Louis De Broglie suggested that wave-particle duality applied not only to light but also to all fundamental sub-atomic particles. De Broglie showed that an electron in orbit around a nucleus could have wave-like properties. In the mid-1920s, physicists Davisson and Germer at the Bell Telephone company produced experimental proof for Louis's equations. They concluded that all matter particles have wave-like characteristics, and the wavelength of these matter particles is equal to Plank's constant. The wavelength is so minuscule we cannot feel it in everyday life. Thus De Broglie's observation laid the foundation for Erwin Schrodinger to lay down the fundamental equation of Quantum Mechanics. Why do particles behave like waves? Let's repeat the double-slit experiment but this time with an electron beam, and see what happens. Yes, you guessed it. We get the same interference pattern again! Why is this the case? Maybe the electrons somehow interfere with each other, so they don't arrive in the same places. Strangely, even when you shoot the electrons one by one so that they have no chance of interfering, you still get an overall pattern that resembles the interference pattern of a wave. Let's place a detector by the slits to see which slit an electron passes through. It gets even more bizarre when we do that. Once we set the sensor, the screen pattern turns into two strips' particle pattern resembling the bullet experiment. The interference pattern disappears. It's almost like they don't want to get caught! What does the experiment tell us? It suggests that what we call "particles," such as electrons, somehow merge characteristics of particles and elements of waves. It also indicates that observing or measuring a quantum system has severe effects on the system. The enigma of precisely how that occurs creates the measurement problem of quantum mechanics. When modern physics found out all sub-atomic particles, including protons, electrons, etc., possess wave-like characteristics, it changed everything we knew so far. It raised questions like what happens to the wave property in the macroscopic realm? If all matter has wave-like properties, why don't we see it in everyday life? These questions about the wave property of matter led to the various interpretations of Quantum mechanics, including the Copenhagen interpretation and the many-worlds theory, which are popular even today. Schrodinger's equation and the probabilistic universe: Austrian Physicist Erwin Schrodinger is one of the forebears of Quantum mechanics. In January 1926, Schrödinger published the paper "Quantization as an Eigenvalue Problem," which presented the Schrödinger equation. The Schrödinger equation determines how these so-called matter waves behave over time. Erwin Schrodinger suggested that matter waves are "smeared out electrons." Imagining electrons smeared out around an atom was almost inconceivable even to physicists. In the same year, Max Born independently concluded we must interpret these waves only through probability. In places where the wave's magnitude is large, the areas are likely you can find an electron. Places where there's less or no wave magnitude mean no electron there. It led to the conclusion that, "we must describe matter itself in a probabilistic manner. These probabilistic waves are what we call the wave function of a particle. What does it mean to have a probabilistic universe? Schrödinger put forward an equation that governs the shape and the evolution of these probability waves, and it changed everything. Many, including Einstein, didn't like the idea of introducing probability into fundamental physics. In one of physics' most quoted statements, Einstein rebuked the quantum stalwarts saying, "God does not play dice with the Universe." In Einstein's view, the universe had no room for an element of chance. But experiment after experiment convincingly confirms that Einstein was wrong. As Stephen Hawking once said, "Einstein was confused, not the quantum theory." But, the debate about what quantum mechanics means continues to this day. Everyone agrees on how to use the equations of quantum theory to make accurate predictions. There is no consensus on what it means in reality to have probability waves, nor how a particle "chooses" its path, nor even whether it indeed chooses or instead breaks off into an ever-expanding field of parallel universes. But it is clear that the universe unfolds itself only through probability, where everything becomes blurry and indeterministic. Further reading: Einstein, Bohr and the war over quantum theory As far as Quantum mechanics is concerned, there is no shortage of weirdness. We have not yet dealt with so much more weird stuff, like the uncertainty principle, Feynman's sum of paths, Quantum tunnelling, Quantum entanglement, etc., which we would discuss in the upcoming posts. Thank you for taking this journey with us as we dive deep into the strange but fascinating areas of physics. If you like to read more from us, you can check out our other posts and subscribe to our newsletter for regular weekly updates.

A simplified introduction to quantum mechanics

Quantum mechanics is a conceptual framework for understanding the microscopic properties of the universe. There is a quote by Niels Bohr,...

26 Feb 2021
Let's talk about how the solar system formed from the proto-planetary disk. It took millions of years to form the solar system, as it took the sun to attain its main sequence stage. The sun and its family evolved together. But the foundations for the modern solar system emerged when the sun was still a protostar. Though they are products of the same molecular gas cloud, planet formation and the sun's genesis took two totally different paths. Sun took more of a top-down approach, from being a giant gas cloud to being carefully chipped down to form a glorious golden yellow star. And planet building is more of a bottom-up approach since they were built brick by brick from the proto-planetary disk. We know the planets formed one molecule at a time through agglomeration and accretion processes. But even after decades of research, astronomers cannot agree on the timescales involved in the various stages, or on the sequence in which the events took place. The beginning of our story is when condensation of the proto-planetary disk started. The same annoying phenomena that cause water molecules to cloud your reading glasses closely resembles the planet making process. It all begins in the solar nebula about 2,200,000 years ago. This animation shows how material around a young star is shaped into planets over billions of years. Credits: NASA's Goddard Space Flight Center Video. From rocky planetesimals to proto-planets: Let's spin the clock backwards. The sun hasn't formed yet; the solar nebula is a hot, dense soup of unique elements. While gases like hydrogen, helium, carbon and oxygen were everywhere, heavier stuff such as silica, methane, water and ammonia were also abundant. Metals were present in traces here and there, but not uniformly distributed. Places surrounding the young sun are a seething 2000 degree Celsius. Only the densest materials like iron can condense to form particles at this temperature. Further out in the planetary disk, silicate particles (fundamental material in rocks and sand) condense and form dust like shreds. Far beyond, near the present location of Jupiter, ice fragments accumulated. Astronomers call this region the 'snowline'. Beyond the snowline, the temperature dropped dead to a mere 70-degree Celsius, allowing only gases like methane and ammonia to condense and form ice crystals. At this point, the proto-planetary disk is a swirling storm of iron, sand, ice dust and snow spinning at thousands of kilometres per second. At this nerve-racking speed, some shards fasten on to its neighbours through electrostatic forces. This process kept ongoing. In a few thousand years, millions of pebble-sized rocks formed throughout the disk. The pebble-sized rocks collided and merged to form mountain-sized planetesimals in the next thousand years. These planetesimals grew larger by attracting more matter from the disk with their own gravity. As more and more material gathered up, protoplanets the size of our modern moon occupied the disk. Further reading: Planets a brief introduction Formation of the Gas giants and the asteroid belt: We know there are eight planets in the solar system. But have you ever wondered which one of them came first? Well, planets grew at different rates in the solar family, but Jupiter came first. The reason is so simple you'll be in awe. The snowline had a tonne of icy planetesimals, and what's ice if not sticky? Take a fist full of sand and a fist full of ice and grip them. You will get your answer! Yes, ice is twenty times stickier than silicate particles. Therefore, planetary agglomeration happened more readily and efficiently, where there was more ice. The first planet of the solar system, Jupiter, was born. It began as an enormous ball of ice and gas, about fifteen times larger than the modern earth. Proto-Jupiter was a giant child that had nothing to do but eat. It swept in all the material and kept growing until it formed a clean orbit around the sun. Jupiter kept on growing for another million years. Its growth stopped at 300 earth masses, not because it ran out of material but because the sun had reached the T-Tauri phase. The violent T-Tauri sun blew out strong solar winds that swept all the material out of Jupiter's path, preventing further growth. A giant disk of gas and dust similar to the solar nebula but smaller surrounded Jupiter. The planetary giant bullied out the leftover planetesimals out of orbit, which formed the present-day asteroids. Saturn formation closely resembles Jupiter. But as everything happened too far away from the sun, it made the process way too slow. The material got swept away in its earlier stages, hence the planet remains smaller than Jupiter. Formation of the Ice giants and comets: Three million years have passed since Jupiter and Saturn had emerged, but the proto-planetary disk is still active. The terrestrial planets were still in their planetesimal stages, two frozen earth-sized kernels formed beyond Saturn. Neptune and Uranus ceased what little gas was available and established themselves as whole new planets in the next 10 million years. The leftover planetesimals got tossed beyond Neptune, making the modern comets. The Oort cloud that envelopes the solar system and the Kuiper belt are the two comet reservoirs where countless comets orbit the sun. According to the nebular hypothesis, the outer two planets may be in the "wrong place". Uranus and Neptune are in a region where the low density of the solar nebula and longer orbital times make their formation extremely unlikely. They must have formed in orbits close to Jupiter and Saturn, where more material was available and migrated outward to their current positions over hundreds of millions of years. Formation of the Terrestrial planets: The Terrestrial planets Mercury, Venus, Earth, and Mars are the latecomers to the party. While the gas planets and the ice giants formed within ten million years, the terrestrials the formation process took longer. Once the early rocky planetesimals had emerged, they gravitationally attracted fragments of the nearby wreck. About one million years later, several large rocky, metallic protoplanets occupied the inner Solar Nebula. And by 10 million years these protoplanets had grouped through gravitation so that only four dominant spheres remained. These, at last, were the primitive terrestrial planets Mercury, Venus, Earth and Mars. But they were only half the size they are today. Tens of millions of years later, even after the sun had started the main sequence, the terrestrials kept growing. It took perhaps 100 million years for the terrestrial planets to mop up the debris, double their masses and rise to their present diameters. Now we know how the planets formed, but a few questions remain unanswered. How did the planets get their satellites? Why the terrestrial planets don't have regular satellites? How did Saturn grow a ring system like no other planet? And much more we will answer in the upcoming weeks. Thank you for taking this journey with us. If you wish to join our weekly mailing list, subscribe to our website. Further Reading: Detailing the formation of distant solar systems with NASA's Webb Telescope by Claire Blome Understanding Our Place in the Universe: Math Professor Verifies Centuries-Old Conjecture About Formation of the Solar System By Worcester Polytechnic References and sources: 1. Formation and evolution of the Solar System From Wikipedia, the free encyclopedia 2. The story of the solar system, book by Mark A. Garlick

Formation of the solar system in 4 simple steps

Let's talk about how the solar system formed from the proto-planetary disk.

22 Jan 2021
The Cigar Galaxy, also known as Messier 82, is situated roughly 12 million light-years away in the constellation Ursa Major. It is about five times brighter than the entire Milky Way and has a galactic core hundred times more brilliant than our galaxy's centre. Messier 82 or M82 was first discovered by Johann Elert Bode on 31 December 1774; he described it as a "nebulous patch", " of very pale and elongated shape". We previously believed the cigar galaxy to be an irregular one because it's visible to us only in sideways. But in 2005 we discovered its two symmetric spiral arms through near-infrared (NIR) images. It is prone to many supernova explosions, induced by the collapse of young, enormous stars in it. Also, M82 is an outstanding example of a starburst galaxy. Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: J. Gallagher (University of Wisconsin), M. Mountain (STScI) and P. Puxley (National Science Foundation) What is a starburst galaxy? A galaxy going through an unusually high star formation rate, compared to the average star formation rate in other galaxies, is a starburst galaxy. In a starburst galaxy, stars form so rapidly that it will gobble up all its star-forming fuel much earlier than it's supposed to. Usually, starburst character is just a phase that takes up a short period of a galaxy's evolution. But sometimes it's different. Most starburst galaxies detected are in a merger or close encounter with another neighbouring galaxy. In our case, M82 is being directly influenced by its gigantic neighbour, the spiral galaxy M81. Tidal forces caused by gravity have distorted the cigar. This process began nearly 100 million years back. This interplay has induced star formation to multiply tenfold compared to regular galaxies. What is happening in the cigar galaxy? A phenomenon called galactic superwind, or just galactic wind, are pretty common in starburst galaxies. Thousands of stars popping into existence all at once ejects a mighty superwind that blasts material into intergalactic space. These high-velocity cosmic winds are usually a result of newly formed large stars or supermassive black holes. But that is all the usual stuff. What is new this time? The latest research reveals that magnetic fields around the galaxy add to the ejection of material from Messier 82. The discoveries from NASA Stratospheric Observatory for Infrared Astronomy, or SOFIA, describe how dust and gas can travel from within galaxies into intergalactic space. The starburst galaxy enriches this material with elements like carbon and oxygen that support life. Then the winds eject this enriched material into the interstellar space to act as building blocks for new stars and galaxies. They presented this research at the American Astronomical Society meeting held between 9-12th January 2021. How did they do it? SOFIA has studied the magnetic fields near the Cigar galaxy's core before. But this time it was a novel approach. Scientists used heliophysics instruments, specifically designed to study the magnetic fields around the sun to understand the magnetic field’s strength around the galaxy. Using the High-resolution Airborne Wideband Camera(HAWK+), SOFIA found that the superwind draws the galaxy's magnetic field perpendicular to the galactic disc. But what researchers really wanted to know something broader than that. The sun exhibits two types of emissions; the solar winds and coronal loops. Solar winds blow outwards from the sun and keep on extending throughout space. But the coronal discharge ejects from the sun and bends back again, forming loop-like structures. They wanted to know if the magnetic field lines would extend endlessly into space like the solar wind, or simply hit the galaxy again to form coronal loop-like structures we see in the active regions of the sun. They have found that the galaxy’s magnetic fields indeed spread out like the solar wind, letting the material blown by the superwind to slip into intergalactic space. Why is this something remarkable? About half a century ago, scientists developed methods to accurately deduce magnetic fields from the sun’s surface. Using SOFIA data, the research team changed this approach to determine the magnetic field about 25,000 light-years away, around the Cigar galaxy. These magnetic fields can reveal how gas and dust observed by space telescopes travel so far away from the galaxies. NASA Spitzer Space Telescope detected dusty material 20,000 light-years beyond the galaxy, but it was a mystery why or how it had reached this far away from their stars in both directions. We now know that the magnetic fields around galaxies have acted as a highway, creating pathways for galactic material to spread far and wide into intergalactic space. This research helps us understand how the intergalactic space became rich in life-supporting elements for subsequent cosmic generations. Subscribe to our mailing list for more trending physics updates! Source: Magnetic ‘Highway’ Channels Material Out of Cigar Galaxy

Do you know what’s causing massive gas and dust ejections in the Cigar galaxy?

The latest research reveals that magnetic fields around the galaxy add to the ejection of material from Messier 82.

18 Jan 2021
It took thirty million to 50 million years to form the star we call the sun. Which may sound like a long time, but in the universe's scale, it is not so long. With lots of help from science and its advanced tools, we know a good deal of how stars form in the universe. One star’s birth starts at another stars' death. Stars die in one of four ways, either they become brown dwarfs, blow up as supernova or become neutron stars or black holes. Whichever way a star finally meets its doom as a supernova, it throws its material back into the galaxy. Over billions of years, this stellar debris gathers themselves into the colossal clouds that astronomers call interstellar matter. The universe is the transcendent recycling machine. Starting around 4660 million years ago, from the remnants of exploded stars, a new one finally rose: a star known as the sun. Recipe for a star: Take 104 solar masses of molecular gas. Sprinkle liberally with carbon and silicate dust spiced with metals. Freeze to 10 K and stir well until mixture is frothy. Hammer until lumpy. No need for oven; stars will form and bake themselves. Watch out for hot bubbles flying from the pot. —James Kaler, “Cosmic Clouds” Further reading: How stars are formed? , The Ultimate guide to understanding black holes Giant Molecular Cloud Time zero 4.6 billion years is the age of our sun. But the process for making this star started way before that. About four thousand million years ago, our solar system was nothing but a cloud of raw materials. Each and every object we see around us from the small meteors that fall in from the sky to planets like Jupiter and even the sun itself came from this gas cloud. The layers of the sun formed one after the other from this parent cloud. These accumulations of interstellar gas were as common billions of years ago throughout the universe. We call them giant molecular clouds. The name is because hydrogen exists in a molecular form in these clouds. Molecular clouds are 73% molecular hydrogen; rest is helium, with traces of heavier stuff like carbon, nitrogen and oxygen, and silicate particles. This ancient cloud from which the solar system born was about 50–100 light-years across, orbiting the core of the Milky Way, about two-thirds of the way out from the centre. These enormous molecular clouds hold enough matter to outweigh millions of stars like the sun. A molecular cloud's life is like thin ice, forever on the brink of destruction. A push, a pull, a tug, anything could trigger enough drama to create an entire star system in these things. Two or more Molecular clouds may smash into each other triggering cloud collapse each other, or a supernova explosion close by can send shock waves from the dying star burrowing into the cosmic mist. Something like this triggered star formation about 4660 million years ago in one of the spiral arms of the milky way galaxy, and it led to the formation of our local star, the sun. Formation of the Solar Globule: Time- 2 000 000 years: Once the collapse molecular cloud starts, it does not stop until an abundance of nuclei forms in the regions where the density is higher. About two million years have passed by now, and denser areas pull in more gas from their surroundings. The parent cloud now fragments into thousands of small concentrated regions. Most of these regions would later form stars, and one of them would become the sun. As the gas closest to the cloud's centre fell inward, the core became hotter. The final inevitable result was a gas and dust cocoon: a shell of dark material surrounding a denser, warmer core. We identify such an object as a Bok globule. Solar globule is the one from which the sun formed. This cocoon-like formation of gas and dust served as an incubator for the young sun. The name might sound ironic as of now because the solar globule was dark. It emitted no light but infrared radiation. Protosun formation: Time: 2 030 000 years Over thousands of years, the gases got pulled relentlessly towards the dense core at the centre. The centre is now about a 10 000 degree celsius, and it is hot enough to emit radiation. The generated radiation makes the globule opaque the heat radiation generated in the core gets trapped inside. As energy could no longer escape, the nucleus heats much faster, and the core shrinks in size. At this point, the nuclear reactions started at the stellar core, and it had reached a form that astronomers call the protostar. Or in our case, we can call it the proto-sun. The gases the proto-sun accumulates over the years don't just stand there, but they start to swirl because of the angular momentum. As the protosun grows smaller and hotter, it spins faster and faster. The Solar Nebula formation Time: 2 130 000 years Within 100 000 years after the protosun formation, the entire gas cloud has become a swollen semi-spherical mass, flattened at the edges by rotation. Over the years, the accelerated rotation has flattened out the gases. Now, an immense pancake-looking disk of swirling gas and dust encircles the protosun. The whole thing now almost resembles a sunny-side-up egg. We call this structure the Solar Nebula. The central region, closer to the protosun, the temperature topped 2000 Celsius. But at about the current location of Jupiter, the temperature dropped below 70 degree Celsius. And further beyond that, it was even more frozen. This chilling disk of dust and debris surrounding the protostar would act as the raw material for planet formation in the distant future. We call this cold, vast accumulation of matter as the proto-planetary disc or proplyd for short. Most of the stuff from the parent cloud fell into the protosun and the rest into the proplyd. The globule surrounding the star had disappeared for the first time, and it revealed the newly forming star to the outer cosmos. It was still a toddler among other giants, but preparing itself for the next–and most violent–stage in its early life cycle: the T-Tauri phase. Further reading: The story of the solar system and how it formed The T-Tauri Phase Time: 3 million years Three million years have passed after the initial collapse of the cloud. The protosun has shrunk itself into a smaller radius. The core temperature is now a whopping 5 million degrees Celsius, while the exterior boiled and churned at around 4500 Celsius. It is no more a protostar, but it is what we call a T-Tauri star. The name may sound like a fancy sushi restaurant, but the T-Tauri phase is one of intense ferocity. A powerful magnetic field drives this phase. Let me show you how the magnetic field of the sun forms. The gases around the young star get ionised and become a mix of positively and negatively charged particles. As the star rotates, these particles create a series of enormous electric currents. Thus the spinning star develops a magnetic field. But what is so violent about it? During the T-Tauri phase, the star would spin at a much faster rate than it is spinning today. It made the T-Tauri sun's magnetic field much intense than what we see today. And the proto-planetary disc sun was wrapping still around it. So, as the sun swirled around, it dragged its magnetic field throughout the disc. Where ever the magnetic field touched the proplyd, enormous clumps of gas got sucked right into the young sun. And where ever these hordes of the gas hit, the agitated star gave out violent flares that are the trademark events of the T-Tauri phase of star formation. Thus the adolescent sun was very much more violent than the star we know it today. The sunspots that on the solar surface were very much larger than what we see today. Possibly the most striking aspect of the T-Tauri phase is the molecular outflow which would come next. The Bipolar Outflow Time: 3 million years At the T-Tauri phase, the sun developed what we call a stellar wind. The sun still has recurring stellar winds. What are stellar winds anyway? It is an ocean of charged particles that stream out from the solar surface. But T-Tauri winds are much more violent and hold more mass, travelling at speeds of up to 200 kilometres per second. As the wind crashed away from the young sun’s surface, the disc carried the flowing gas further away into space. Because of this violent activity, charged, accelerated particles began strutting away from the young sun at both the poles. Astronomers call this a bipolar molecular outflow. The sun lost much of its original mass through this process. However, the sun continued to shrink under gravity because the pressure at its heart was not yet enough to halt the shrinkage. By the time the wind had stopped, 10 000 years had passed, and the sun’s mass started to stabilise. But the sun still has tens of millions of years before it is wholly mature. Further reading: Check out this insightful post by Jillian Scudder The sun won't die for 5 billion years, so why do humans have only 1 billion years left on Earth? The Main Sequence phase: Time: 30–50 million years After 30 to 50 million years, the sun’s contraction finally stopped. The sun’s inherent temperature had struck a whopping 15 000 000 Celsius. And at 15 000 000 Celsius, the positively charged hydrogen nuclei at the sun’s core started speeding up. This marks the beginning of the nuclear fusion reaction in the sun's core. Let me explain the reaction occurring in the sun, making it shine. Being at the centre of the sun, an enormous amount of mass encases you, squeezing down on you from all sides. Similarly, the hydrogen gas in the sun's core gets crammed in so rigorously that four of them fuse to form one helium atom. We call this nuclear fusion, which converts some mass of the hydrogen atoms into energy as light. The sun's core produces the same amount of energy as 15 billion hydrogen bombs each second. It doesn't blow to pieces because the gravity just precisely balances tremendous energy produced. The fusion reaction slowly converts the hydrogen into helium in the sun’s nucleus through a series of nuclear reactions. The output of these reactions is nothing but pure energy. The core is now a self-sustaining mass that has now produced a considerable amount of energy in its nucleus. The pressure created by this reaction was so intense the gravitational contraction finally met its equivalent. As the power precisely matched against any further gravitational contraction, the sun had reached hydrostatic equilibrium. It had become a stable star, what astronomers call a main-sequence star. It took tens of millions of years for the sun to get to this point. About 4600 million years later, it is not quite halfway through its main-sequence journey. It still has a long life ahead. Thank you for taking this journey with us, as we take a deep dive into the secrets of the universe. And if you want to read more from us, there’s always a subscribe button somewhere nearby! Want to know what happens when the sun dies? Check out this amazing post by Michelle Star in this link: https://www.sciencealert.com/what-will-happen-after-the-sun-dies-planetary-nebula-solar-system References: The story of the solar system, book by Mark A. Garlick Catching Stardust_ Comets, Asteroids and the Birth of the Solar System, book by Natalie Starkey

Sun 101: How the brilliant yellow star formed from just a cloud of gas

About four thousand million years ago, our solar system was nothing but a cloud of raw materials.

16 Jan 2021
How mind-blowingly awesome it would be to have three suns to orbit around instead of one? This new planet called KOI-5Ab, (Yes! it needs a better name) has exactly that and much more. Though triple star systems are not so rare, this discovery deserves a special place, especially because this planet has a skewed orbit. What did they discover? The NASA Kepler mission at the beginning of its operations in 2009 spotted a planet about half the size of Saturn in a multi-star system. KOI-5Ab was the second planet detection from the mission, and exciting as it was they ultimately set it aside as Kepler went on discovering thousands of planets. By 2018, it had discovered an impressive number of 2,394 exoplanets, and an additional 2,366 exoplanet candidates that need confirmation. KOI-5Ab got mostly forgotten because it was complicated and Kepler had found many other easy pickings to research. But advanced observations from the second planet-hunting mission TESS (Transiting Exoplanet Survey Satellite) and many ground-based telescopes, have researched KOI-5Ab and confirm its existence. There are some fascinating details about this planet to ponder. KOI-5Ab is unique because it orbits a triple star system, circling on a level, out of alignment with at least one star. It makes us wonder how everything in this system formed out of the same swirling clouds of gas and dust. How did scientists confirm KOI-5B as a planet? Data from the W. M. Keck Observatory in Hawaii, Caltech Palomar Observatory near San Diego, and Gemini North in Hawaii determined that KOI-5b planet is circling one of the triple-stars in the system. Still, they could not figure out if the signal was a mistaken glitch from one of the two other stars, or if the planet was real. Then, in 2018, TESS came to help. Like Kepler, TESS seeks the flickerings of starlight which occurs when a planet passes in front of a star. To confirm the elusive object is indeed a planet, scientists went back and re-investigated all the data, and then sought further cues from ground-based telescopes. Unlike TESS and Kepler observatories, scientists often use the Keck Observatory for follow-up searches of exoplanets. Keck measures the faint tremble in a star as a planet passes around it. Stars too experience the gravitational tug from the planets orbiting them as they move around. An exoplanet collaboration group called the California Planet Search examined for any wobbles in Keck’s data on the KOI-5 system. They detected a wobble generated in the inner companion star by the planet as it orbits the primary star. They confirmed that KOI-5b is indeed a planet that orbits its star roughly every five days. Here are the orbital mechanics of the triple star system, KOI-5Ab (planet) orbits Star A, which has a neighbouring companion, Star B. The Stars A and B orbit each other every 30 years. A third gravitationally captivated star, Star C, orbits stars A and B every 400 years Here's a detailed post on the GW Orionis triple star system from Phil Plait for further reading: A TRIPLE-STAR GRAVITATIONAL DANCE CREATES RIDICULOUSLY COMPLEX SCULPTURES A skewed orbit around the star: The data also shows that the orbit of the planet seems unaligned with the Star B. Because of the bent orbit, it is hard to determine whether the whole star system formed from the same gas cloud. Astronomers are not sure what caused the misalignment of KOI-5Ab. But they think that Star B, kicked the planet during its development stage, disrupting its orbit and causing it to move inward. Scientists believe modern tools, such as the Palomar Radial Velocity Instrument at the 200-inch Hale Telescope at Palomar, the NASA and National Science Foundation’s NEID instrument in southern Arizona and the Keck Planet Finder will expand our knowledge about exoplanets. Source: Planetary Sleuthing Finds Triple-Star World

Kepler finds a forgotten Planet in a Triple-Star system

How mind-blowingly awesome it would be to have three suns to orbit around instead of one? This new planet called KOI-5Ab, has exactly that.

12 Jan 2021
In 2020, astronomers detected an exotic cosmic object known as a magnetar. Further investigations through NASA Chandra X-ray Observatory tells us the magnetar is also a pulsar. Let us learn about Neutron stars, pulsars, magnetars and what the recent study implies. Neutron stars, Magnetars and Pulsars: What are Neutron stars? Neutron stars are one of the most extraordinary and violent things in the universe. Almost like black holes, Neutron stars form when a massive star over eight times the mass of our sun star runs out of fuel and collapses under its gravity. When the central core of the star collapses, it squeezes together with an enormous, titanic force. The pressure involved is immense; it crushes even the subatomic particle, such as protons and electrons, forming neutrons. These newly formed neutrons stop any further gravitational collapse and give birth to a neutron star. But Neutron stars form only when the disintegrating star core is somewhere around 1 and 3 solar masses. Stars with core masses more than that will continue their collapse giving birth to stellar-mass black holes. There are many neutron stars found scattered throughout our galaxy. But they are quiet and mostly go undetected because they barely emit enough radiation to make it to our telescopes. But we find the absolute best kind of neutron stars in binary star systems. They spread out energy as gravitational waves, ripples in spacetime, their orbits can collapse, and they can crash into and kill each other in a kilonova explosion that spews out their guts. When they do, the conditions become so extreme that, for a moment, they make heavy nuclei again. The heavy neutron-rich matter falls apart and reassembles into heavier elements. These explosions are probably the origin of most of the heavy elements in the universe, like gold, silver, uranium, platinum, and much more. Magnetars and pulsars are the commonly existing types of neutron stars types which we can detect. What are pulsars? Pulsars are the most widely detectable neutron stars. Pulsars are neutron stars that rotate. As their name suggests, pulsars emit pulses of radiation at somewhat regular intervals. When neutron stars first collapse, they spin very rapidly, like an ultra-high-speed top. Pulsars have a potent magnetic field because of the density of matter present in them. The region surrounding the pulsar dominated by its magnetic field is the magnetosphere. When charged particles like electrons and protons, or atoms pass near the magnetosphere, they speed up to extraordinarily high velocities. When charged particles accelerate, they radiate light. This process causes the magnetosphere of the pulsar generates light in the optical and X-ray range. Neutron stars that give off long-lasting radio beams are the radio pulsars. What are Magnetars? Magnetars are neutron stars with tremendously strong magnetic fields. When compared to earth, their magnetic fields are quadrillion times stronger. This magnetic field generates a pressure that disrupts the stellar surface resulting in starquakes. These disruptions release bursts of X-rays and gamma rays we can observe through our devices on earth. There are currently 30 magnetars known in our galaxy and the Magellanic Clouds. NASA's Chandra X-ray Observatory's recent discovery: On March 12, 2020, the NASA Neil Gehrels Swift Telescope detected a new magnetar; this is the 31st magnetar observed among the 3000 known neutron stars. After follow-up observations, researchers named it Swift J1818.0-1607. The Swift mission found J1818.0−1607 when it took off its peak activity. In this stage, its X-ray radiation became ten times brighter than usual. These outbursting events mostly start with a rapid increase in brightness over days or weeks, then declines as the magnetar returns to its normal brightness range. Astronomers must act fast if they want to observe peak activity from one of these rare stars. The Swift mission alerted the global astronomy community, XMM-Newton and NuSTAR performed quick studies. Magnetars not only emit X-rays but also release magnificent bursts of gamma rays and can also emit steady beams of radio waves. (Gamma rays are the high-energy form of light in the universe and radio waves are the lowest energy form of light in the universe) What is special about magnetar Swift J1818.0-1607? Chandra’s observations of J1818.0-1607 gave astronomers the first high-resolution view of this object in X-rays. The magnetar is at a distance of about 21,000 light-years from earth. The following facts are its special features, It is the youngest known magnetar. Astronomers have estimated its age to be about 500 years old. Second, it also spins faster than any known magnetar. The rotation takes place at the rate of once every 1.4 seconds. Astronomers have also observed J1818.0-1607 with radio telescopes and discovered that it gives off radio waves as well. J1818.0-1607 also has properties similar to that of a slowed down radio pulsar. Less than 0.2% of the known magnetar population also act like pulsars. The explosion that created a magnetar of this age would have left behind visible debris. But scientists have found potential evidence for a remnant at an enormous distance away from the magnetar. In order to cover this distance, the magnetar would need to have travelled at speeds far exceeding those of the fastest known neutron stars. Chandra’s observations in less than a month after the discovery with Swift has given astronomers the first-ever high-resolution image of this magnetar in X-rays. Diffuse X-ray emission surrounds the point of detection. This effect is possibly caused by X-rays bouncing off dust in the star's vicinity. The emission may again be from the winds rushing off the neutron star itself. The below composite image comprises a wide field of view using infrared observations from the Spitzer Space Telescope and the Wide-Field Infrared Survey Explorer (WISE), taken before the magnetar’s discovery. X-rays from Chandra highlights the magnetar in purple for visibility. Read more from NASA's Chandra X-ray Observatory.

Astronomers found the youngest and fastest spinning magnetar ever detected

Scientists at the Chandra X ray observatory have detected a rare type of neutron star

12 Jan 2021
The sun plus its eight planets, their satellites, asteroids and comets make up the solar system. This post is the first of the many articles that will explore the properties, distances, comparisons, when and how things formed in the solar system. In future posts, we will discover what the Solar System has undergone since its violent beginning. And, finally, we shall see what will befall them in the distant future, four or five billion years from now, as the yellow star we call the sun passes into old age. These and other matters are all part of a marvellous story; the story of the solar system. The solar system- an overview: Does our solar system have a shape? Where are its celestial bodies located? How do the planets and their satellites move relative to each other? These questions are paramount when we learn about our star system. When I started the research for this series of articles, I found what I already knew was just a drop in the vast ocean. And there is much more to learn, so let us begin. The heliocentric model: Let's first get this simple thing straight; the sun lies at the centre, and all the objects within its gravitational influence go around it. It is now a well-known, well-established fact, but before the Copernican era, people believed otherwise. The human civilization believed that the earth was at the centre of the solar system for at least 1500 years. In 1543, when Nicolaus Copernicus proposed that the sun was at the centre, he faced severe religious opposition. He had deferred from publishing his data and research till the year of his death. While it was revolutionary putting the sun in the centre, his planetary orbits were incorrect. Decades later, the German astronomer Johannes Kepler found the planets do not move in circular orbits, but their orbits are slightly elliptical. Now we have a more refined understanding of the solar system. Let me summarize below what we know so far. The sun is at the centre, and all the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and other dwarf planets) move around it in an anti-clockwise direction. The sun itself spins anti-clockwise. Only Neptune and Venus rotate in a clockwise direction. All of them go about in elliptical or near-circular orbits around the sun. The moons have the same orbital and spin directions as the planets. The four planets closest to the sun known as the terrestrial planets; they are rocky and metallic. The next four planets are collectively known as the Jovian planets. Jupiter and Saturn are gas giants; Uranus and Neptune are ice giants. These giant planets possess orbits ten times larger than the sizes and trajectories of the terrestrial planets. The solar system is flat, for instance, its flatter than a dinner plate. It looks almost like a flattened disc. Asteroids are also a part of the solar system. These are unevenly shaped chunks of metal and rock, found mainly between Mars and Jupiter forming a region known as the asteroid belt. The comets are small icy bodies, have two homes. Some creep beyond Neptune in a disc called the Kuiper belt. Trillions of comets exist a thousand times farther from the Sun than Pluto. They surround our galaxy in an enormous spherical structure known as the Oort cloud that envelops our solar system. Theories of the origin of the solar system: The theory about the origin of the Solar System was first proposed in 1755 by the German philosopher Immanuel Kant (1724–1804). He worked out that, the sun and the planets formed from an immense rotating disc of gas and dust that appeared from a cloud of interstellar material. Pierre-Simon, marquis de Laplace (1749–1827), famous for his demon, independently came up with the same idea 54 years later and perfected it. He interjected that the rotation would produce an angular momentum in the cloud, causing it to flatten out. The sun would emerge at the centre, while the planets would form further out in the disc, condensing from concentric rings of material shed by the central star. This theory of origin became known as the nebular hypothesis. The widely recognized contemporary modification of the nebular theory, the solar nebular disk model (SNDM) offers explanations for a variety of properties of the Solar System. The nebular hypothesis clearly explains the disc-like heliocentric system with planets in neat orbits, but the theory has its imperfections. Video credits: Simulating Solar System Formation | California Academy of Sciences Drawbacks in the Nebular hypothesis: The sun, like all the planets in the solar system, rotates in its own axis. For the Nebular hypothesis to be correct, the sun should spin 400 times faster than the current rate. Astronomers call this the angular momentum problem. How planetesimals form is the most significant unanswered puzzle in the nebular disk model. How 1 km sized planetesimals form from 1cm sized specks remains a mystery. Understanding this mechanism might also point out why some stars are gifted with planets, while others have nothing. The Nebular hypothesis does not account for extra-solar planets, also known as exoplanets, their formation remains mysterious. The nebular hypothesis does not apply to other planetary systems other than ours. Other star systems seem to have Jupiter like planets known as hot Jupiters close to the star, and they have short orbital periods (only a few hours). The bottom line is, there is nevertheless a long way to go before we have a model that can rightly reproduce the observed characteristics of every known planetary system, including ours. Until then, the nebular hypothesis is the best we have. What we have learnt so far is only the beginning, in the next part of this solar system series we look inside our local star and try to understand everything about it! Stay tuned and subscribe to our weekly newsletter to stay updated.

Nebular Hypothesis-The story of how the solar system formed

This post is the first of the many articles that will explore the properties, distances, comparisons, when and how things formed

8 Jan 2021
NASA spinoff technologies are products and services developed with help from NASA, through research, licensing patents, employing NASA equipment or technical support from NASA personnel. In brief, the NASA Technology Transfer Program uses NASA resources to produce commercial products known as spinoffs. According to the NASA spin off the website, since 1967 they have published over 2,000 spinoff technologies in various fields such as computer technology, environment and agriculture, health and medicine, public safety, etc. According to some urban legends NASA invented Tang, Velcro and Teflon, which is incorrect. But they did come up with well-known products such as memory foam, freeze-dried food, firefighting equipment, emergency space blankets, Dust Busters, cochlear implants, LZR Racer swimsuits, CMOS image sensors, etc. Let's discuss a few upcoming spinoff technologies from NASA for 2021. #1 Traffic Management system for drones: NASA Ames has created a traffic management system for drones a.k.a Unmanned Aerial Systems (UAS), to maintain reliability and efficiency. This unique technology allows non-military drones to operate more efficiently at lower altitudes. We could use this system for the delivery of goods and services, agricultural imaging and surveillance. Benefits: • Helps drones to communicate, navigate, and survey below 10,000 feet • Airspace engineering to keep drones separated from each other and other flight operations. • Plans routes to avoid conflict, accidents, land obstacles, harsh weather, and wind-based difficulties. #2 Sun-powered propulsion: NASA Glenn laboratory is working on and has expertise in small solar electric propulsion (SEP) systems. This low-power, high throughput SEP rockets are small space crafts with an advanced magnetic circuit design. They are a game-changer in thruster performance. They can maximize efficiency and minimize cost; effectively. Glenn can grant this facility to private U.S. businesses through a free, non-exclusive license agreement; this can boost U.S. market position in the electric propulsion division. Benefits • Fuel productivity • Reduced size • Powerful propulsion • Long life • Satellite versatility • Space cargo transportation • Space exploration and research #3 Spacesuit Robotic gloves: Researchers at Johnson Space Center have designed spacesuit gloves to increase both strength and flexibility. These gloves have actuators to maintain a better force output, better efficiency, higher reliability and greater thermal spectrum than commercially available actuators. The robotic gloves have position sensors for accurate grasping, and it has a built-in restorative force to support moving back into a comfortable, non-grasping position. Industries such as manufacturing and healthcare can benefit from these robotic gloves. Benefits • These gloves can help develop recovery aides and help patients with diminished hand strength. • It can help in tools operation and carry out manual labour for a long duration. #4 Versatile Broadband Antenna Researchers at Marshall Space Flight Center have created a unique patch antenna technology. This manageable antenna design presents meaningful benefits to satellite communication applications. It offers an exclusive wide-band/multi-band operating facility and broadband capacity. Patch antenna technology helps commercial space or non-space applications where stable signal strength and smaller antenna sizes are crucial. Benefits • It supports wide-band operation across multiple frequency bands, with high-gain signal strength and offers hemispherical coverage • It is small, thin, and can be conveniently manufactured in a simple, multilayer device. #5 High-Flow Cleaning Cleaning up can be a nightmare both in households and in industries. Especially in powder-based additive manufacturing techniques, every component must be debris free, from the surface to crevasses. The task becomes bleak and time-consuming when there are so many and complicated parts. Not with NASA's invention! High-flow cleaning uses an enormous quantity of pressurized air to enter the cleaning chamber. The high-flow results in powerful air velocity, and when this airflow passes through smaller component crevasses, it removes residue powder from the part. Benefits: • The process is fast and automated. It cleans parts in minutes, instead of hours or days. • CT-scans of cleaned parts showed that this method is very efficient for debris removal. • It works best on complex parts. The system gets rid of remnant powder lodged in small grooves and passages encountered in complex mechanical components. #6 Composites for Extreme Environments: Innovators at NASA's Glenn Research Center have developed silicon carbide (SiC) fibres and ceramic matrix composites (CMCs). We can use these fibres in high-temperature treatments, such as components in gas turbine engines. These fibres can withstand very high temperatures. NASA's copyright(ed) SiC CMC technologies bring in materials that can withstand adverse structural and environmental conditions for prolonged periods and temperatures up to 2,700 degrees Fahrenheit. These composites are favourite because of their versatility. We can modify and re-engineer them for specific stress, temperature, life and environmental conditions. #7 Passive Porous Tube Irrigation System: The Passive Porous Tube Nutrient Delivery System is like the drip irrigation system. The plant growth system distributes a nutrient solution to the roots of plants through capillary movement. The process is designed and tested for microgravity. A ceramic tube and water-filled nutrient bags are connected in a loop, and it requires no electricity or moving parts to function. It pumps the nutrients in through capillary force. The porous tube furnishes the plants with the water and nutrients needed to germinate and grow. It is an autonomous plant growth device that is easy to put together, farm, and harvest, reducing the amount of intervention required in traditional farming. Benefits • Decreases the labour required in regular farming. • It delivers precisely, what plants need and nothing more. • Ensures over-or under-watering does not occur. • It does not require electricity or any moving mechanical parts. Jim Reuter, the Associate Administrator Space technology Mission Directorate has said that Transferring NASA technology beyond the space agency is part of our mandate and our longest-standing mission. Spinoff 2021 may look slightly different, but the message is not: we are always working to ensure our innovations find the fullest benefit, from space to you. We may expect more innovations from NASA that can improve our lives. All the technologies mentioned above can be licensed from NASA for commercial production and distribution.

7 NASA spinoff technologies to look forward to in 2021

The NASA Technology Transfer Program uses NASA resources to produce commercial products known as spinoffs.

5 Jan 2021
Everyone knows our solar system is a part of the milky way galaxy, have you wondered what the milky way galaxy is or how it formed? In this post, we dive into the depths of our home galaxy and get to know it better. Before that, let us answer a few simple questions! What is a galaxy and how they form? What is a galaxy? A galaxy is this magnificent arrangement of gas, dust, stars, remnants from dead stars, interstellar medium and dark matter (Yes! Dark matter is real) all bound together by gravity. All this matter rotates around the galactic centre which may or may not contain a supermassive black hole. Our solar system is a part of the galaxy we call the milky way. We derive the word galaxy from the Greek word 'galaxias', it means 'milky'. The ancient Greeks looked up the night sky and discerned the obscure, hazy band of light as the milky way. In 1610, this view changed, when Galileo Galilei viewed the cosmos through his telescope lens. He was the first to discern the hazy band across the night sky as individual stars. For many years from there, until the 1920s, People believed that the milky way was the entire universe; they thought there was nothing beyond that. But modern science has taken us far beyond the naïve understandings of the universe. What we now know is astounding compared to the ancient Greek's knowledge of the cosmos. We now know the milky way is a galaxy that contains a hundred thousand billion stars with their own planetary systems. We have learned that the Milky Way is a spiral galaxy with an estimated visible diameter of almost 1.9 million light-years. It is a part of the local group called the Virgo supercluster among 700 similar galaxies. And it is one of the 100 billion such galaxies in the observable universe. We now know we are not even microbial specks in the grand scale of the universe, yet we contemplate the wonders of the cosmos. Take a moment to relish this fact, and we shall learn about all the types of galaxies that exist in the Universe. What are the different types of galaxies? We classify galaxies based on their size, shape and structure. Dwarf galaxies are the most common type, they contain around a few million stars. Dwarves are the most commonly occurring type. Giant galaxies are less common and can possess more than a trillion stars. We also classify galaxies based on their shape and appearance, the main types are elliptical, spiral and irregular. One-third the galaxies in the visible universe are elliptical; they can appear almost circular or very elongated. These galaxies have little interstellar material, and therefore less active. Scientists suspect them to have formed because of the collision of two are more galaxies. A shell galaxy is a type of elliptical galaxy where the stars arrange themselves in concentric shells. We see Shell structures only in elliptical galaxies but never in spiral galaxies. The shell-like arrangements form when a larger one swallows its smaller companion galaxy. Spiral galaxies appear flat even though in reality they look like a sunny side up egg. The centre has a bulge of stars, gas and dust. A band of stars run through this bulging centre of some spiral galaxies, we call these the barred spiral galaxy; the milky way belongs to this type. Spiral galaxies contain a lot of interstellar material hence actively form stars. Irregular galaxies are neither elliptical nor spiral. They have noticeably less interstellar medium and are less active. These are the earliest galaxies to have appeared in the universe. How galaxies form? Things in the universe take time (a LOT of time!) to happen, it is hard for us to witness anything forming from its initial state, within the human lifetime. Even medium-sized stars like the sun take tens of millions of years to form; colliding galaxies take billions of years to merge. Despite all this, we have a pretty clear understanding of how the universe works. We can look out and see different versions of similar events happening in various places. All this is possible because light takes time to get here. We simply have to look out to see the history of the universe written all over it. We know that from the big bang; the universe started at a remarkably orderly, homogenous state. The early universe had mostly large clumps of dark matter. Even though we have made a ton of observations over the past few decades, scientists haven't concluded the exact mechanism that explains galaxy formation. But they put forward two not so different approaches to deal with this. The ELS theory put forward by Olin Eggen, Donald Lyden Bell and Allan Sandage suggests that the galaxies form when a gigantic cloud of gas collapses. This is the top-down approach. The other theory suggests that larger clouds collapse into smaller clouds and these smaller gas clouds develop into individual protogalaxies. Many protogalaxies merge to form the larger galaxies we see today. This is the bottom-up approach to galaxy formation. There is also a third possibility which we will discuss next. The below visualization shows small galaxies forming, interacting, and merging to form Milky Way-type galaxies with spiral arms. Credit: NASA/Goddard Space Flight Center and the Advanced Visualization Laboratory at the National Center for Supercomputing and B. O'Shea, M. Norman Why is there a black hole at the centre of every galaxy? Whether galaxies came together as gas and then began forming stars or whether stars formed from little gas clumps and then assembled into galaxies is uncertain. But there is another possibility we need to consider. We know that black holes result from stellar death. When stars with core mass greater than 8 solar masses, collapse under their own gravity, resulting in black holes. These are the most common types of black holes whose mechanism most scientists agree upon. Scientists believe that there are ten million to a billion stellar black holes in the Milky Way alone. But these are not the only black holes found in the universe. Apparently, we have supermassive black holes, which are millions to billions, of times as massive as the sun. Supermassive black holes lie at the centre of almost every galaxy including our own Milky Way. We believe the formation of supermassive black holes involves a chain reaction of collisions of stars in dense star clusters that results in the evolution of immensely massive stars, which then collapse to form intermediate-mass black holes. The star clusters nearby then sink into the galactic centre where the intermediate-mass black holes fuse to form a supermassive black hole. Another possibility is that black holes could have appeared before the galaxies formed. The black holes that emerged before the galaxies could have swept up material all around forming galaxies we see today. And galaxies formed from the surrounding gas that did not get sucked in by the supermassive black holes. The centre of the Milky Way galaxy, with the supermassive black hole Sagittarius A* (Sgr A*) located in the middle, is revealed in this image. (Credit X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI) What are satellite galaxies? In the universe, not only planets possess their own satellites, but galaxies have them too. Galaxy's satellites are not boring old rocks but they are entire galaxies themselves. Not only billions of stars in a galaxy orbit the galactic centre, sometimes dwarf galaxies of lesser mass go around the giant galaxies; astronomers call these satellite galaxies. A satellite galaxy is a smaller partner galaxy that travels on bound orbits within the gravitational range of a more massive primary galaxy. Satellite galaxies are bound to their host or primary galaxy, much like the moon is gravitationally bound to Earth. About fifty satellite galaxies orbit the milky way galaxy, the Large Magellanic Cloud being the hugest among them. Below is an animation illustrating the discovery history of satellite galaxies of the Milky Way over the last 100 years. The classical satellite galaxies are in blue and more recent discoveries are in green. What happens when galaxies collide? Galactic collisions are quite common in our universe and happen all the time. In this sense, the word collision does not take the literal meaning but refers to the gravitational interaction between two or more galaxies. This collision may have different results depending on the size of the colliding galaxies. When larger galaxies interact with their satellite galaxies, they might become locked with one of its spiral arms. If two galaxies collide and do not have enough momentum to continue travelling after the collision, they merge and become one galaxy; they plunge back into each other and ultimately merge into one larger galaxy. If one of the colliding galaxies is much larger than the other, the bigger one will look the same, while the smaller galax gets shredded apart and becomes part of the larger one. Astronomers have predicted the Milky Way Galaxy will collide with its galactic neighbour the Andromeda Galaxy in about 4.5 billion years. The two spiral galaxies will ultimately unite to grow into an elliptical or possibly a massive disk-like galaxy. The distance between stars would make it improbable that any of them will individually collide, but the collision will eject some stars from the resulting galaxy, nicknamed Milkomeda or Milkdromeda. How do galaxies die? We know galaxies are nothing but a vast collection of stars and star systems. Does a galaxy die when all its stars die? Not exactly, but we consider a galaxy dead when it runs out of fuel to produce new stars. Most elliptical galaxies have burnt out their star-making fuel and are prominent examples of fossil galaxies. Elliptical galaxies burnt up all their reserves of star-forming gas, and all that is left are the longer-lasting stars known as red giants. Eventually, over extensive lengths of time, those stars will blink out one after the other, and the whole thing reaches the background temperature of the universe. As long as galaxies have gas for star formation, they will keep on flourishing. Once the fuel runs out or a dramatic merger uses all their star-forming gas, they are gone!

Galaxies 101- the past, present and future of the milky way galaxy

Everyone knows our solar system is a part of the milky way galaxy, have you wondered what the milky way galaxy is or how it formed? In...

29 Dec 2020
In 1944, the physicist famous for killing cats in his thought experiments Erwin Schrodinger thought about the question 'what is life'? There was no such thing called biophysics or astrobiology back in his days. He naturally tried answering a few questions in biology from a physicist's point of view. Schrodinger had views mainly about two aspects of life, one is genetics, and the other is thermodynamics. In his analysis of genetics, he estimated the number of atoms in a gene, then suggested that it encodes the genetic information in something resembling an aperiodic crystal-like structure. Schrödinger also proposed that organisms can create ordered systems within themselves, by producing even higher disorder in the environment. We will talk about order and disorder quite a lot in this post, let's save it for later and proceed. What is life? The answer to this fundamental question might vary depending on the person you ask. If you ask a philosopher, a biologist and a physicist, the same thing their answer might differ. The best way to go about this is to understand life through its properties. What are some properties of life that separates them from the inanimate world? Self-replication: Self-replication is one of the remarkable properties of life that makes it stand out. A table doesn't find a matching table, have sex and produce more tables, but a rat living under that table does! All life on earth is a consequence of replicating genes. Living organisms are chemical systems: It takes living organisms a plethora of biochemicals to carry out life functions whereas, a robot requires machinery, components and software to function. Evolution: Before including evolution into the equation, let's consider the fact that not all self-replicating systems are alive. For instance, take crystals, they are also self-replicating chemical systems, are they alive? No! Evolution is a fundamental property of life that has adaptability etched into it. If the offsprings produced through genetic replication is not perfect, it offers the organism a choice through genetic mutations; those mutations might offer a better chance for survival or might not. Therefore, we can conclude that life is a self-replicating chemical system capable of evolution. Before getting into the physics of life and all that, let's understand the requirements for life. What are the requirements for life? Life requires a rich source of elements and compounds that can support its energy, protective and reproductive requirements. Life needs a solvent in which the elements and compounds can mix and combine to form more complex organic biomolecules. A solid surface or a liquid substrate to live in and carry out functions of life because dense organic molecules cannot stay afloat forever. And importantly, life needs the energy to sustain itself! Did we originate from stardust? As we read in the article about the Big Bang, none of the heavier elements needed for life formed in the early universe. 3,78,000 years after the big bang, protogalaxies formed, these were the earliest seeds for all the galaxies, star clusters, planets and black holes we witness today. The Big bang left us with a universe that had an abundance of the most basic gases, hydrogen and helium. These gases acted collided and clumped together, forming the first protostars. Because of the plethora of hydrogen and helium available, the first generation stars were exceedingly massive. We learnt in the life cycle of stars that, the more massive stars have a shorter life. Stars that had eight times the mass of our sun, the temperature rises enough to form heavier elements than just hydrogen and helium, Materials such as carbon, oxygen, magnesium and silica form in their cores. This fusion process continues till the core forms iron; hitting iron means the star has hit rock-bottom and further fusion cannot occur. The energy produced at the core halts abruptly and the core shrinks, this sends a shock wave throughout the still fusing outer layers of the star, causing it to explode in a grand explosion called a supernova. These events can outshine entire galaxies. It produces elements heavier than iron in stars and disperses through supernova explosions. Supernovas can enrich stars and planetary systems with material that can lead to formation and sustenance of life. Through the above process, our planet got its rich supply of various elements, compounds and metals. How planets formed? Now we have all the material needed for life, but where do they go? Planets are the splendid abodes for life. Let's examine how planets form around stars. Protostars develop a flat disk-like cloud of dust and gas that rotate around them, called an accretion disk. Material floating in the disk eventually bombard and clump together forming millions of protoplanets. These protoplanets fuse to form planets. The inner region of the accretion disk that is closer to the star receives more heat from it. Hence non-volatile elements that don't evaporate away easily are abundant here, and they formed the rocky planets such as Mercury, Venus, Earth and Mars. These planets are rich in iron, Aluminum and silica, making it more suitable for life. The outer region of the accretion disk receives less heat from the star and gets an abundance of volatile material that stays in gaseous or liquid states. Hence formed the gas giants like Jupiter, Saturn, Uranus and Neptune. How did life on earth originate? Even though we don't yet have the exact mechanism of how life originated on earth, we sure have some plausible theories. Scientists believe life formed near hydrothermal vents deep inside the ocean. The ancient earth without life on it wasn't pretty to picture; it was teeming with UV radiation and volcanic activity. Hydrothermal vents are these fissures on earth's surface where molten lava meets seawater inside the earth's ocean. Seawater seeps into these vents and immediately pushed back outside because of the tremendous heat. But the seawater that comes out is just not plain old seawater anymore; it's now a wealthy slurry of minerals and chemical compounds. All this make hydrothermal vents a strong candidate for facilitating the origin of life. There is an alternate approach to this idea; we know it as panspermia. It suggests that organic matter formed outside earth and was bought here through asteroids or meteors. We have checked most of the 'requirements for life' list; there's just one more left, that is energy. Energy part is simple to understand. But before getting to that part, we need to understand the entropy behind it. What entropy has to do with life? We learnt about entropy when we learnt about the arrow of time and how the big bang is the ultimate source of low entropy in our universe. Entropy is the measure of disorder in a system or entropy is the universe's way of pushing towards its much-coveted state of equilibrium. We also learnt that according to the second law of thermodynamics, the entropy in the universe always increases. But what about life? Life on earth seems ordered. Since the formation of the first living cell to the evolution of human beings, the level of orderliness has relentlessly increased. Doesn't this violate the second law of thermodynamics? Let's take it slow from here. Even though life has an extreme amount of order within it, it contributes to the universe's increasing entropy. To understand this, let's go back to the classic example of the broken egg. Imagine you have an unbroken egg, the egg has low entropy, and high energy concentrated within it. Now you accidentally leave the egg somewhere near your puppy. Is the egg going to stay whole when you come back? No! You get back to a splattered, half-eaten egg on your carpet. The energy concentrated in the egg before has spread out throughout your carpet and has high entropy. There is no way you could put this energy back together, and it is a one-way process. From this, we understand that energy never randomly concentrates in one place, unless there is a living organism behind it. Living organisms do this all the time; they have somehow figured out how to accumulate energy and even store it. How life exchanges entropy for energy? Living organisms act to reduce their internal entropy by borrowing energy from the sun. According to physics, living organisms are this high functioning entropy maximizing machines. Life is a process feeding on low entropy; for life on earth, the sun acts as a source of low entropy. This idea first came from Ludwig Boltzmann, who observed that life is a struggle for entropy; more accurately a struggle for lowering entropy. The most arbitrary form for energy is thermal radiation. Plants absorb the concentrated energy from the sun (source of low entropy) and convert it into high entropy and heat. Animals consume high-energy-density packets of matter called food and convert it to lower energy density waste and that same heat. Therefore, all living forms, including the microbes, gather energy and give back heat and entropy; keeping the second law of thermodynamics alive. The ultimate source for the low entropy for the universe is the big bang itself. The universe must increase its entropy to reach equilibrium, all systems, including our universe, prefer to attain the boring state equilibrium where nothing happens. While the universe takes its grand steps of distributing energy and reaching equilibrium, these systems of extreme order like stars, galaxies, planets, moons, life naturally arises; we are a rare and precious part of it. References: 1. Astrobiology: A Very Short Introduction Book by David Catling 2. From Dying Stars to the Birth of Life: The New Science of Astrobiology and the search for life in the universe Book by Jerry L. Cranford 3. First Life: Discovering the Connections Between Stars, Cells, and How Life Began Book by David W. Deamer 4. Astrobiology: A Brief Introduction Book by Kevin W. Plaxco and Michael Gross

How to understand the physics behind life on earth?

Lfe is a self-replicating chemical system capable of evolution.
Lets understand the physics underlying life on earth and how it works.

17 Dec 2020
Time is something that everyone is familiar with 60 seconds is one minute, 60 minutes is one hour. We know this as linear time and is something that everyone is acquainted with and agrees upon. Time crumbles things; everything grows old under the power of time and is forgotten through the lapse of time. - Aristotle. Understanding time according to physics packs a different story. Let's jump right in. What is 'time'? What is the best way you can define time? What is time in a general perspective? If someone asks you to draw time, what would you draw? You would probably sketch a regular old clock or perhaps an hourglass. But hourglasses, pendulum clocks, very recent atomic clocks are all only ways to measure time. We understand from this time is not a physical object, but a mental concept. Time is one concept we are very familiar with, but why is it so hard to define it? Because time is far more complicated than you realize. For now, let's stick to the definition that time is something that we measure using clocks; it represents a flow of events from past, to present, to future. How did the concept of time evolve? According to the legends of classical physics such as to Newton or Gallileo, time was something absolute. In their world, there was something called 'absolute time'; it is not subject to any kind of change. There is one flow time for the entire universe, events take place in its grand, absolute order. One could with little irregularities measure time, and it would be the same for everyone irrespective of their distance or state of motion. It was an elegant and complete picture to imagine. But this is physics, it never allows us to have a perfect uniform picture of the world. When everything looks near perfect, someone comes in and messes it up; then we rewrite everything we know. This view of absoluteness of time changed when Einstein (Yes, it is him again!) published his equations of special and general relativity. It views time as a phenomenon inexplicably tied to space. General relativity regards time as the fourth dimension and ties it into a mathematical framework called space-time. Hold on tight, it gets real spooky from here. Changing your perspective of time: Before stepping into the bizarre world of moving clocks and gravitational impact, you need to let go of some of your previous understandings of time. Let's take this one step at a time. Does absolute time really exist? General relativity put an end to absolute time. Time does not flow at a constant rate throughout the universe, but it dilates. Time dilation is the slowing down of time that occurs under the effects of gravity or motion. Hence, if you are moving through space, your passage of time is slower than a stationary person. Also, if you are nearer to a massive object, like the earth, the sun or a black hole; the immense gravitational pull from that object causes your time to slow down. Your one second is a bit longer than the one second of the person sitting on the top floor of Burj Khalifa. The time difference is minimal, like a billionth of a second but at enormous distances and faster velocities, the difference is profound. Read our other post, The 5 step guide to understanding space-time to understand time dilation effects in detail. What is now? If you and your friend sitting at the top of Burj Khalifa, don't experience the same flow of time, it automatically takes us to the next question; What does 'now' even mean for us? We now know that your one second and her one second is not the same. Well, now means nothing in the universe's scale. Let's perform a brief thought experiment. Let's borrow your friend sitting at the top of Burj Khalifa and put her near the star Proxima Centauri; that is approximately 4 light-years away from us. It takes light, four years to reach us from Proxima Centauri. Imagine somehow you can see her just by looking at the sky and you see her cooking in her kitchen. What you are seeing is not what she is doing right now, but what she was doing 4 years ago. Anything you see now has already happened. This bizarre event is because light takes four years to reach you from Proxima Centauri. If you are looking at the moon, you do not see how it is now; you are seeing how it was 1.5 seconds ago, the sun 8 minutes ago and some stars ten thousand to many billions of years ago. What does all of this bizarreness of reality tell us? The notion of our present is our own, and it does not correspond with the universe. 'Present' exists only in our little bubble; not extended and same throughout the universe. What is 'now' is a meaningless question in the universe's scale. The universe is simply a collection of events not ordered in time. What is time according to the laws of physics? The laws of physics do not differentiate between the past, present and the future. Even if we take everything in our universe and change its fundamental constituents into anti-matter particles, the laws of physics would remain the same. Even if we reverse the order of events, the laws of physics do not change. The physics describing the splattering of an egg can be, with little change, be used to describe un-splattering of an egg. The laws of physics do not discriminate between the past, present and the future. The fundamental equations of Newton, Maxwell or Schrodinger do not have the time variable. This brings us to the conclusion that we do not need time to describe how the world works on a fundamental level. What does that even mean? If physics treats time indifferently, why is our experience different? Why do we continuously experience the flow of time in daily life? Let's learn why. Is time an illusion? We know quantum physics explains the tiniest constituents of nature. Quantum mechanics and general relativity treat time in different ways. The Wheeler-Dewitt equation of Quantum mechanics does not include time at all. Would that mean that time does not exist, at the most fundamental level? Below the value called Plank time (10-44 seconds) quantum effects of time begin to manifest. Among particles that make up the universe, time seems to work and flow in every direction; both forward and backwards. There is no telling which event happens before or after. At quantum scales, our understanding of time breaks down. If time does not exist among the fundamental particles, how does it come to be on the macro scale? Is time real or could time just be some sort of illusion generated by the limitations of the way we perceive the universe? We simply do not know. Do we really experience the flow of time? What if we put you in a dark room without windows and ask you the same question? Will you know how much time has passed? You probably don't know, you can only speculate. We human beings, experience time as change. Changes do not happen in a second, they happen gradually through time. Imagine we leave you in the same dark room with an apple or a candle. You now know how much time has passed by looking at the candle or the condition of that apple. Change marks the passage of time. The question is not whether or not time passes; the real challenge is, why it always moves in a single direction. You are constantly travelling through time, one moment to the next, whether or not you like it. What is the arrow of time? In our universe, the flow of time clearly is a unidirectional arrow. Apples rot, but don't go back to their initial fresh state, candles melt but do not un-melt, eggs break but don't un-break. These events, even though it is theoretically possible, do not go in the reversed direction. How to understand this? However, in the set of fundamental equations, there is one equation that differentiates past from the present. It is the second law of thermodynamics that indicates time in fundamental physics. According to the second law of thermodynamics, the sum of entropy in a system always increases. You might ask, what the heck is entropy? The answer is simple; Entropy measures the amount of disorder in a system. High entropy means the system is highly disordered and low entropy means the system is highly ordered. The direction entropy that always flows from low to high marks the direction of 'the arrow of time'. In our universe entropy of a system always increases. Eggs do not un-break, people don't un-age, apples do not un-rot. When we apply this low to high entropy to the universe, there arises an even bigger problem. What is the source of all this entropy? What entropy has to do with the big bang? The big bang is one of the most plausible theories we have regarding the beginning of the universe. Time began at the Big Bang. What it tells us is this, By the time the universe was 2 minutes old, it was in a highly orderly state, filled with 75% hydrogen, 23% helium and small traces of deuterium and lithium. Conditions that were present at the beginning of the universe play a crucial role in determining the arrow of time. The universe from the big bang began in a state of low entropy (extreme order), this state is the source of the order we currently witness. Here's how to understand this view: If the universe began in a state of high entropy, the levels would go down from there or, it will remain constant. Instead, our universe started in a regular, very smooth and ordered state; which leaves us with a condition of increasing entropy since the beginning of time. Future is not only what's about to happen next; it is the direction of increasing entropy. The arrow of time starts only at low entropy and flows towards increasing entropy. How this highly ordered state came to existence is still a question that is left to be answered by modern cosmology. Let's wrap up! We have learnt that time has a different rhythm in every other place and passes accordingly, and there is no single absolute time. The intrinsic difference between past and future does not exist at the fundamental level. The notion of now does not work in the vast universe, there is nothing that we can reasonably call present. Entropy never decreases in the universe. And the direction of the increase of entropy determines the direction of flow of time. What we don't know is the conditions that made big bang itself possible. We don't know how time, with the characteristics we witness now, came into being. There's no law of physics yet that states that time did not exist before the Big Bang but it is the beginning of 'time' in our universe. Conditions similar to the Big Bang could explain the arrow of time and the origin of our universe. However, to answer these questions, we need to unite quantum mechanics with Einstein's theory of general relativity; which we haven't figured out yet. This would provide a precise link between the quantum world of atoms with the macro-world we live in, including the stars, galaxies and black holes in the universe. We call this "the theory of everything" and it is the holy grail modern physics. Thank you for taking this journey with us. Stay tuned until we explore some mind-bending concept next week. If you want to get notified there is always a subscribe button somewhere nearby. Research and references: 1. A BRIEF HISTORY OF TIME From the Big Bang to Black Holes. By Stephen W. Hawking. Illustrated by Ron Miller. 198 pp. New York: Bantam Books. 2. THE ORDER OF TIME. By Carlo Rovelli, Penguin; 1st edition (26 April 2018) 3. The Fabric of the Cosmos: Space, Time, and the Texture of Reality (2004) Book by Brian Greene The Nerd stuff works hard to keep advertisements minimal and create a non-intrusive learning experience for our readers. If you want to buy the books above for further reading, please use the links below.

The spookiness of time and how to understand it

What is the best way you can define time? What is time in a general perspective? Time is not a physical object, but a mental concept

10 Dec 2020
Evolution has engineered human beings to think, to contemplate, be curious and ask questions. We base our entire existence on asking questions. All our discoveries and innovations came to us because we had questions about everything; Many of those questions solved a plethora of problems. There does not exist a human being who hasn't contemplated the existential questions like, What is this vast expanse called the universe? Why do we even exist? Does all of this have a meaning? How did we all end up here?. For most people, these questions are spiritual. But for some of us, these questions are scientific. Even if the open windows of science at first make us shiver ... in the end, the fresh air brings vigour, and the great spaces have a splendour of their own. BERTRAND RUSSELL, What I Believe Some of us reconcile with the fact that the universe is the way it is whether or not we like it. For those who prefer the brute facts of science, it does not disappoint. Science tells us that the universe came from almost nothing as a quantum fluctuation, with a big bang. Big Bang is the only theory of the universe supported with evidence. Let's take a deep dive into what we know about the origin of the universe. A brief history: Till the 1920s, scientists including Albert Einstein believed the universe was static, eternal and comprised a single galaxy called the milky way; surrounded by an infinite, dark and empty space. But general relativity later painted a new picture of the universe even Einstein himself could not believe. Now almost everyone knows that our universe is expanding and our galaxy is one among 400 billion galaxies in the observable universe. Soon after general relativity got published by, scientists started applying relativity to real-world problems. When Karl Schwartzchild adopted those equations for point masses with infinite densities, it led to the discovery of black holes. Alexander Friedmann, a Russian cosmologist and mathematician, developed the Friedmann equations from Einstein field equations, pointing that the universe might be expanding in opposition to the static universe model favoured by Albert Einstein. In 1924, American astronomer Edwin Hubble; based on astronomical observations proved that the universe was expanding. In 1931, Georges Lemaître went beyond just an expanding universe and suggested something extraordinary. If we extended the expansion backwards in time, it would lead us to a smaller universe with mass concentrated into a single point. He called the early universe a primaeval atom, from which the fabric of space-time came into existence. But how does this Big Bang work? How can something come from nothing? Before that, there are a few clarifications to make. A few clarifications: First, the Big Bang was not an explosion; names can be misleading. It was the space itself expanding everywhere all at once. The universe started extremely small and rapidly expanded to the size of a watermelon. The universe did not and is not expanding into anything, but the fabric of space itself is stretching. The universe cannot do so because it has no boundaries. (For example: Imagine a balloon with small dots sketched on it; when you inflate the balloon the dots get bigger. It's not because the dot has expanded but the area where the dot sits has expanded, making the dot look bigger. Same way, space itself is expanding sweeping all the galaxies along with it) There is, by sense, nothing outside the universe because the universe is all there is. Asking 'what exists before the big bang?' makes no sense at all. Singularity : As per observations of scientists, the universe started from an infinitely hot and dense gravitational singularity. We know little about this singularity. It requires both General relativity and Quantum mechanics combined to understand this singularity state. As we learnt in our previous post about gravity, Scientists are struggling to bring General relativity and Quantum mechanics into one fold. Singularities exist in the centre of black holes. The Plank Era: We know the period between 0 to 10^−43 seconds into the Big Bang as the Planck epoch. During this phase, the four fundamental forces (the electromagnetic, the strong nuclear, the weak nuclear and the gravitational force) combined into one. In this stage, the universe was only about 10^−35 meters wide and had a temperature of roughly 10^32 degrees Celsius. At 10^−43 seconds, gravitation separated from the other forces and the universe cooled down a bit. The universe was pure energy at this stage; it was ragingly too hot for any particles to form. Matter and energy were not just theoretically equivalent but were practically the same stuff. Equal amounts of matter and Anti-matter (yes they are real!) pairs formed and annihilated each other. At a point, slightly more matter particles formed than antimatter and couldn't annihilate as they didn't have pairs to do so. Those loners served as the ultimate source of matter to create galaxies, stars and planets. Please take a moment to relish that by now, only one second has passed since the beginning of everything. Big Bang Nucleosynthesis: As the universe expanded and cooled, it needed to hit a sweet spot to facilitate the formation of elements. If too hot, the atoms formed would instantly tear apart; too cold, no reaction would take place. Between 10 to 1000 seconds after the big bang, the temperature dropped one billion degrees to 100 million degrees Celsius; the sub-atomic particles such as protons, electrons and neutrons formed in its hot forges. The nuclear fusion reaction we all learnt in 8th grade is enough to understand the formation of atoms during the big bang. Nuclear fusion reaction takes place inside every star; it's a process in which two light nuclei combine to form a heavier one, releasing an enormous amount of energy. As we read in the 'life cycle of stars', fusion not only creates energy but it also additional elements. As the cosmos continues to cool—dropping below a hundred million degrees—protons fuse with protons and with neutrons, forming atomic nuclei and producing a universe in which ninety percent of these nuclei are hydrogen, ten percent are helium, along with trace amounts of lithium. None of the elements that facilitate life formed in the Big bang; the carbon in your body, the oxygen you inhale, the metals in your kitchen tableware and the uranium used in nuclear power stations—was all once forged in the fiery furnaces inside stars. We are star-dust! Following nucleosynthesis, the universe existed as a hot, dense plasma of atomic nuclei, electrons and protons. The light could not pass through this hot plasma; any atom that formed got ripped apart. This state continued for 3,80,000 years. Recombination and the cosmic microwave background (CMB): Magic happened when the temperature of the universe fell below 3,000 degrees. The phase called recombination allowed electrons to bind with the nuclei forming the first-ever atoms. The universe became transparent when the last scattering took place. The photons trapped within the hot dense plasma freed themselves and traversed across space. Astronomers can see this light from the early universe that is virtually unchanged for over 13.5 billion years today. This super-cooled microwave radiation called the cosmic microwave background is just 2.73 degrees above absolute zero (-270 degrees). Robert Wilson and Arno Penzias of Bell Laboratories, New Jersey accidentally discovered this leftover radiation from the Big bang while they were trying to eliminate a faint cackle caused by it. The photons from the big bang are all around us. The cosmic microwave background accounts for 99.99% of radiation in the entire universe. For every photon produced in a star, there are 10^32 photons left over from the big bang. If someone tells you that they don't believe in the Big bang, tell them there is proof right in front of us. We see the Big bang! (Feel free to use our infographics for educational purposes or share in social media. Don't forget to credit us with a link) Pre-Big Bang-A Universe from Nothing: The idea for the universe created from nothing lies in the quantum realm. It suddenly appeared where once there was nothing at all. Sub-atomic particles can blink in and out of existence all the time. Their sudden, almost magical appearances have a price to pay; greater the energy of the particle formed, faster it disintegrates. That is more energy borrowed, shorter the life. Nature plays with strict rules here. If you borrow energy, you need to give it back; if not, you die. Higher the sum you borrow, shorter gets your life. But if we borrow nothing, it's a different story altogether. According to the law of conservation of energy, the overall energy of the universe sums to zero. If we borrow no energy at all, a universe in principle can pop into existence from nothing. Allen Guth, the proprietor of the theory calls it the free lunch universe. It formed from nothing as a quantum fluctuation; such a universe should have collapsed under its gigantic gravity and soon disappeared. But before that could happen, a grand expansion came to the rescue and pushed it out of the quantum realm before it had any chance to collapse. A universe can create itself from nothing without violating a single law of physics. Structure Formation: During the first billion years, the universe further expanded, and the temperatures cooled down a bit. The matter that existed here and there clumped together and gravitated into the colossal groups we now call galaxies. Nearly a hundred billion of them formed, each comprising hundreds of billions of stars that undergo thermonuclear fusion in their nuclei. (Learn more about the formation of stars here) For the next twelve billion years, the expansion of the universe steadily slowed down as the stuff in the universe pulled on itself through gravity. Some stars, with more than about ten times the mass of the Sun, produce enough pressure and heat in their cores to manufacture heavier elements, those makeup planets and the life that may thrive upon them. Reasons to believe in the Big bang theory: Even though not all the scientists of the 21st century agree that the big bang is how the universe formed, it is still one of the most plausible explanations we have. Here's why. Our microwave telescopes detect background radiation, surrounding us on all sides and virtually perfect and consistent in all directions. It is red-shifted light from a period almost as primitive as the cosmos itself. We can see that the universe is expanding and moving apart, which means it was once much tinier and denser. Physicists and astronomers can determine how fast things are moving apart, and calculate how long before that microscopic, dense state existed. We find Quasars in the galaxies far away from us; light from quasars light up all the stuff in its path, giving us insight about the early universe. In 2011, astronomers found clouds of primordial gas by investigating distant quasars. These two clouds of gas contain only hydrogen and deuterium, but no traces of heavier elements; they likely formed in the first few minutes after the Big Bang. What the Big bang theory not explain? Even though Big Bang theory is one of the ablest cosmological theories, it has its gaps to fill. Big bang tells us that the universe expands from a gravitational singularity. But it does not explain the origin of this state of singularity. We do not know what existed before the singularity. The universe seems to have expanded from an exceedingly orderly, smooth state. We can see this through the uniformity of the cosmic microwave background. We don't know why this is the case. Understanding space and time fully compels us to discover equations that can grapple with the extreme conditions of immense density, energy, and the temperature of the early universe. Many physicists believe, developing a unified theory of physics will resolve this quest. Research and references: 1. Krauss, Lawrence M. (2012). A Universe from Nothing: Why There Is Something Rather Than Nothing. New York: Free Press 2. Parson, Paul (2018). The Beginning and the End of Everything: From the Big Bang to the End of the Universe, Michael O'Mara Books, 2018 3. Big Bang From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Big_Bang 4. Niel Degrasse Tyson, "ASTROPHYSICS FOR PEOPLE IN A HURRY". Kirkus Reviews. March 7, 2017. Retrieved August 5, 2017. 5. A BRIEF HISTORY OF TIME From the Big Bang to Black Holes. By Stephen W. Hawking. Illustrated by Ron Miller. 198 pp. New York: Bantam Books.

Big Bang 101: How a universe formed from nothing

ience tells us that the universe came from nothing with a big bang. Big Bang is the only theory of the universe supported with evidence.

4 Dec 2020
The concept of space-time a great intuition that came from a rare genius of the human mind. As I took my baby steps into the realms of Physics, space-time is where I struggled the most; I think it is natural for most people. We all have a hard time wrapping our minds around the beautiful geometry of space-time. Evaporation is a physical phenomenon a fifth-grader understands; it is because the child sees most of what happens in front of its eyes. We humans don't see space every day and feel how it behaves, nor we are born equipped to do so. Don't feel bad if you are having a hard time. This post is an attempt to simplify the concept of space-time and how it behaves, without getting too technical about it. Instead of jumping headfirst into Lorentz contraction, time dilation and other stuff, it is better to understand space and time separately and then combine their intrinsic nature. Time and space are modes by which we think and not conditions in which we live. -Albert Einstein Step 1: Letting go of Newtonian space and time The Newtonian view or the classical physics view of the universe is outdated. Newtonian mechanics helps us to understand the world to a great precision; it is good enough for day-to-day life. But when we get closer to the grand scheme of things and understanding reality itself, it gets complicated. The classical world view merely blurs our understanding of nature. According to classical physics, space and time are absolute features of reality; they are universal and do not change at any circumstance. To take a step forward, you must take two steps backwards and change your notion of a flat, eventless space where our planet is sitting and the flow of time that is, same for the entire universe. Step 2: Understanding the aspects of Einstein's space: As we read in the previous post about the weirdness of gravity, in the absence of any matter or energy, space could be flat like the smooth surface of a table-when a massive body like the Sun emerges, it causes space to warp. It acts like a rubber sheet that curves when a bowling ball falls on it. A massive object (like the Sun) in space warps its surroundings, this affects other stuff (like planets) in its vicinity and forces them to follow a curved path. Einstein explained how gravity is nothing but a geometric consequence of curved space. The more massive the object, the more distortion it causes; more distortion means more gravity. Einstein's space is dynamic. It is not just a platform for events to take place, but a live arena that reacts to matter and energy. Even in empty space, time and space still exist. - Sean M. Carroll Not only mass and energy cause space to distort, but acceleration too has an effect. Gravitational waves occur because of disturbances in the curvature of space, generated by aggressively accelerated massive bodies (like neutron stars or black holes) that propagate as waves outward from their source at the speed of light. All these effects convert the empty Newtonian space into the bending, curving and fluctuating fabric of space we are all embedded into. We have now pretty much got the idea of how the fabric of space responds to matter, energy or acceleration. Now let's talk about time. Step 3: Letting go of the universal time According to Newton, absolute time and space are solely aspects of reality. The pure mathematical time, also called duration, flows equally throughout the universe with no external influence. It exists independently and advances at a steady run, no matter what. This means absolute time does not depend upon physical events, but it is a backdrop or stage within which events occur. While Newtonian arrow of time flows in a single direction at a steady rate, Einstein's time differs. It is very dynamic, depending on gravity and velocity. Step 4: Grasping 'time' according to Einstein According to General Relativity, time does not flow at a constant rate throughout the universe, but it dilates. Time dilation is the slowing down of time that occurs under the effects of gravity or motion. Time dilation because of motion: To understand time dilation due to motion, you need to understand dimensions. Our universe has three dimensions, this means our realm of reality allows objects to have a length, a breadth and a height. Einstein, with a stroke of genius, added time as the fourth dimension, apparently connecting time with the other three dimensions; it led to the concept of space-time ( a. k. a Minkowski space) To understand the effects of velocity on time, we need to understand shared motion among different dimensions. Have you ever noticed the fact that you are always in motion through the fourth dimension, that is 'time'? Even if you are sitting idly and binge-watching your favourite show on Netflix, you are still moving through time; falling into the hands of the future one second at a time. Now imagine you are moving in a speeding car and binging Netflix; this time you are not only moving through time but you are also moving through space. Your constant motion through time gets shared among all four dimensions; this causes your time to slow down. Therefore, a moving clock ticks slower than a stationary clock. Can you imagine something mind-blowing than this? But there is something! We all know nothing travels faster than the speed of light. A photon (that is light) has the maximum velocity in three-dimensional space; such a particle has no momentum left in itself to move through another dimension. The photon doesn't move through time because it moves through space in the maximum velocity possible. This is why light does not age. A photon produced at the big bag is, to this very moment zero years old. Gravitational time dilation: General relativity predicts that time flows slower when you are near a massive object like Earth. Closer you are to a strong gravitational field, slower your time flows. This is how General relativity gets rid of absolute time. For example, let's consider a pair of siblings who are twins. Think that one of them goes to live on the top of a mountain while the other stays somewhere around the valley. The first twin, living at the mountain top would age sooner than the second. Thus, if they met again, one would be older than the other. Here, the difference in ages would be insignificant, but it would be much greater if one twin went for a long trip in a spaceship travelling close to the speed of light. When she returns, she would be much younger than the one who stayed on Earth. This is the twins' paradox. This is how gravity affects time. The gravitational field is so strong near the singularity of a black hole, time practically stops inside it. Time dilation is not just theory, we use this concept in everyday life. The difference in the speed of clocks at different heights above Earth is now of great importance. We use very accurate navigation (GPS) systems based on signals from satellites nowadays. If you ignore general relativity, the position that a GPS satellite calculates would be wrong by several miles! Step 5: Embracing space-time: Space and time are now far away from being static and absolute and have become dynamic quantities: when a body moves, or a force acts, it influences the curvature of space-time—and the geometry of space-time influences how objects move and forces act. Space-time not only affects everything but also gets affected by everything that happens in the universe. The new understanding of space-time has revolutionized our view of the universe. This is the story of how the notion of a dynamic space forever replaced the initial idea of an essentially unchanging universe, that could have existed forever. This fascinating idea has now given us an expanding universe with a finite past and a finite future. Subscribe to our weekly newsletter for updates! References: Greene, B. The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory., 1999. Print. Hawking, Stephen, 1942-2018, A Brief History of Time. New York: Bantam Books, 2017. Image credits: cover image: ESO/L. Calçada.

The 5 step guide to understanding space-time

This post is an attempt to simplify the concept of space-time and how it behaves, without getting too technical about it.

27 Nov 2020
Black holes, they are one of the fascinating discoveries of modern physics. It is hard to come across something mind-bending, stunning and terrifying at the same time! They have triumphantly entered the mythos of science fiction; writers and creators cannot get enough of them! The internet has a ton of questions about black holes; 'Is it safe to jump into a black hole?' is one of the most searched. I have tried to answer a few questions myself. Here is what we would cover, History of black holes What are black holes? How are black holes formed? Anatomy of a black hole Types of black holes What black holes eat? How black holes die? Excited?! Let's jump right in. A brief history of black holes: We took a picture of a black hole pretty recently; that is in 2019, but the discussion about these celestial monsters started way before that. It was back in 1783 John Michell, English natural philosopher and priest, speculated the existence of black holes; he called them frozen-stars. He thought if we have a large enough star, it should have enough gravity to trap light itself from escaping; which is astonishing for a person only used to Newtonian gravity! In 1915, after ten years of hard labour, Einstein perfected the most elegant, complex and beautiful theory in the history of physics, general relativity. Einstein's equations are till date quite hard to solve, yet the equations were begging for someone to take on the cumbersome task. In 1916, the astrophysicist Karl Schwarzschild found himself mesmerized by Einstein's equations and solved them. The results were stunning to Schwarzschild and Einstein himself. The solution directly pointed to objects what we call today as 'black holes'. American Physicist John Wheeler coined the term 'black holes'; the name stuck. What are black holes? We keep on hearing the term 'black holes' discussed in NEWS at least once a month recently; what are they? A black hole is a region of space where an enormous amount of matter crams into a tiny area resulting in extreme gravity; so strong that nothing, not even light—can escape from it. It means mass with enough density can distort space to form a black hole. If you take earth and crush it down to the size of a soccer ball, you would end up with a black hole. How are black holes formed? The most commonly occurring black holes result from dying stars. As we learnt in the life cycle of stars, stars eventually burn out their fuel and stop shining. Usually, stellar deaths are spectacular events resulting in a planetary nebula or supernova explosions. But when stars with a final mass in the range 2 to 3 solar masses ultimately collapse to form a black hole. We know gravity can do pretty weird things, black holes result from extreme gravity! Anatomy of a black hole: Any black hole has three essential components: a central singularity, an event horizon and an accretion disk. The singularity is the central eye of the black hole. It holds a gravitational singularity in which contains an enormous mass concentrated in an infinitely small space. The central singularity of a black hole is exotic, it is nothing like we have ever seen, experienced or we know of; all the laws of physics we love and cherish breaks down at the singularity of a black hole. The event horizon is the disk that marks the radius of a black hole a. k. a Schwarzschild radius. It forms when light captured by the gravity of the black hole cannot get away and stays hovering at the edge. Beyond the event horizon lies the point of no return; once you cross the event horizon of a black hole, your fall into the singularity becomes inevitable. Stuff, such as gas, dust and other stellar wrecks that have come very close to a black hole but haven't slipped into it, creates a pancake-looking disk of matter whirling around the event horizon; we call this the accretion disk. “The ultimate extreme level of a moment in time is the singularity of a black hole.” ― Khalid Masood Types of black holes: There are four types of black holes classified based on their mass: stellar, intermediate, supermassive, and miniature. Stellar black holes are the most commonly occurring black holes; they form because of stellar death. These are usually three or four times the mass of our sun. Intermediate black holes contain 100 to 1000 times the mass of our sun. A single star could never form such an enormous black hole; scientists speculate they while two black holes collide and merge. We haven't figured out their formation yet. We find supermassive black holes at the heart of galaxies. They usually contain mass a million to billion times the sun. The black hole at the centre of the Milky way weighs 4 million solar masses. Miniature black holes are hypothetical and said to have formed during the big bang and later evaporated. We do not have any proof of their existence, yet. What black holes eat? Black holes are not essentially these cosmic vacuum machines, but they swallow stuff that wanders too close. But when they eat they get fat; the diameter of a black hole is proportional to its mass. If a black hole swallows three times its mass, its diameter grows three times. In Binary star systems, if one star is enormous enough to form a black hole; the other eventually gets eaten. The star that collapses into a black hole doesn't immediately swallow it up, but it waits like a predator that waits for its prey. When the other star burns up its fuel and expands into a red giant; it gets peeled and eaten layer by layer. It doesn't get spookier than this! How black holes die? Black holes don't just suck in everything and live happily ever after; they eventually lose their mass as radiation known as Hawking's radiation. To understand how this works, we have to understand space first. Space is not a vast emptiness as we think it is; it is teeming with particles popping in and out of existence. These particles aren't real; they are virtual particles. Particles form out of thin air in space all the time, but they annihilate soon after. Cool, right?! When this happens at the edge of a black hole, one particle gets drawn into the black hole, and the other will escape. Except, the one that departs becomes a real particle, the one that falls in doesn't. So the black hole is losing energy in the form of radiation. This black hole evaporation happens incredibly slowly at first and gets faster as the black hole becomes smaller. When it has the mass of a mountain, it radiates with about the heat of our sun. In the last moment of its life, the black hole radiates away with the energy of billions of nuclear bombs diffused at once in a tremendous explosion. But this process is exceedingly slow; the black holes we know might take up a googol year (a googol year is equivalent to ten raised to the power of a hundred years) to evaporate. It takes so long that when the last black hole radiates away, nobody will be around to witness it.

The Ultimate guide to understanding black holes

Karl Schwarzschild found himself mesmerized by Einstein's equations and solved them.The solution directly pointed to black holes

22 Nov 2020
“Look again at that dot. That's here. That's home. That's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives - Carl Sagan We live and thrive in this beautiful blue planet called Earth. It feeds us, grows us and nurtures us. Everything we have, we have taken from mother Earth. What do we know about the place that bears us all? Primarily we all know for a fact that Earth is a planet, and it revolves around a star but what are planets? How do planets form? How did our solar system form? Let us step ahead and discuss! What are planets? We cannot just go around any star system and name things floating around as planets, there are guaranteed criteria for any spherical mass to be called one. According to the International Astronomical units (IAU) to be called a planet, the astronomical object must fulfil the following conditions: It should orbit a star. It must hold a spherical shape (hydrostatic equilibrium) It must be large enough so that its gravity clears the path it orbits around the star. According to the above definition, bodies fulfilling all these criteria are Planets. Of course, there is always room for exceptions. Pluto-like planets only satisfy the first two conditions hence placed among "dwarf planets. There is much debate happening around these criteria to define them, as we keep on discovering more and more, our definitions for 'what a planet is?' will also evolve. Let's leave it to the experts for now and move on to how planets form. How do planets form? Though there are millions of planets throughout the Milky Way, we need not look beyond our solar system to understand how planets form. Unsurprisingly, how stars form has a lot to do with how planets form. There are many theories about the formation of our solar system. The nebular hypothesis is the most notable and widely accepted among them. Our Universe is a cornucopia of regions with uneven distribution of gas and dust. These regions are responsible for the formation of structures called Nebula, in our case, it's called the solar-nebula. Solar Nebula is nothing but a giant cloud of spinning at a high velocity. Here's what happens in that cloud of gas and dust. As the cold gas cloud spins at higher velocities, the centre of the gas cloud condenses. Density in the centre increases the spinning speed and results in a flattened out pancake-looking disc called an accretion disc. This animation shows how material around a young star is shaped into planets over billions of years. (Credits: NASA visualization explorer) Eventually, the temperature and pressure at the centre of the disk continue to increase till the central region collapses to form a Protostar. If the accretion disk around the protostar still has matter enough to form an entire star system, it rains its material into the star till it emerges as a Main-sequence star. The material left in the accretion disc continues to spin around the protostar. These particles continue to bombard with one another, forming clumps of material. These clumps stick together till their gravity gathers up even more material, it creates thousands of moon-like protoplanets. Protoplanets continue to grow, gathering up more mass till they form actual large-enough planets that revolve around the star at the centre. Why are planets round? Now we know all planets came from shapeless clouds of gas and dust, but all we see through our telescopes are spherical balls moving about, why is that? Why didn't we get to have conical moons or a giant joystick-shaped Jupiter? That would have been fun right? But nature has its reasons. Candidly "The heavenly bodies are round because Gravity allows them only to be round". Energy and gravity conspire together to make celestial objects round. As Newton famously said, anything that has mass experiences gravity. When gravity pulls equally in all directions, the only shape a body could assume in space is a sphere and nothing else. Types of planets: In our solar system itself, there are mainly three types of planets- they are rocky planets, gas giants and dwarf planets. The inner planets of our solar system are rocky (Mercury, Venus, Earth and Mars) and rest are gaseous (Jupiter, Saturn, Uranus and Neptune). The nebular hypothesis can provide an answer. The heat and solar winds caused by the sun swept the lighter gases farther out into the developing solar system. Hence he rocky terrestrial planets are closer to the Sun, while the gas giants Jupiter Saturn Uranus and Neptune formed in the shivery outer region of the solar system. Pluto falls under dwarf planet category along with Eris, Ceres, Makemake and Haumea. We classify these planets as dwarfs because they haven't cleared the path they revolve around the star. There are other types of planets, such as rogue planets, exoplanets, Trojan planets, Goldilocks planets and more. Stay tuned for more fascinating stories from our Universe. Subscribe to get stories direct to your inbox!

Planets: A brief introduction

What do we know about the place that bears us all? Primarily we all know for a fact that Earth is a planet, and it revolves around sun

9 Nov 2020
I have a heart for every star in the universe. There’s one dying every day, but somewhere in the expanse, there is another emerging -Letara We look up to the night sky we see little stars sparkling like diamonds. It is getting harder to see them with all the flickers and flashes of artificial city lights all around us, stars still fascinate us and have done so for centuries. Stars and constellations meant a lot to ancient civilisations. They marked their calendars with them. They thought they could predict the future through their position in the night sky. Stars could have carried mysteries with them for our ancestors now science has blessed us with knowledge about them. Have you ever asked yourself what are these stars, anyway? How are they formed? How did they even get there in space? Well, I have tried to answer a few questions in this post. Stay tuned! What are stars? Stars are large astronomical bodies found throughout space. Technically stars are these immense spheres of luminous plasma held together by their own gravity. Simply stars are massive spheres that burn from the inside out. This burning produces heat and light necessary for life to thrive. How do stars glow all the time? How do they produce the heat and light that keeps them glowing? Well, they contain lots of hydrogen atoms (the lightest kind of Atom) actively combining with other hydrogen atoms to form Helium. This process is known as Nuclear fusion. Nuclear fusion produces an immense amount of energy as it takes place. This process keeps the star glowing. When the star runs out of hydrogen, they stop shining. Now we know how stars work, but how did the object get there in the first place? How are stars formed? You might think of the Universe as a vast emptiness called space with a few galaxies here and there, that is not the case. Galaxies contain an interstellar medium made of dust and gas called stellar nurseries or Nebula. Imagine a room full of smoke and dust actively combining with each other, the smoke is dense and full of dust at some places in the room and the smoke has less dust in other places of the room. That's how the interstellar medium looks. Similar to the smoke and dust room the interstellar medium also has different densities in different areas. The areas with high-density form molecular clouds. Stars form in these molecular clouds. What are stars made of? Though star formation feels like a complicated mechanism, the recipe for star formation is quite simple. All we need is Hydrogen, Gravity, lots and lots of time, that's it! Why hydrogen? It is the simplest of all elements and it is found in the interstellar medium. Almost 99% of the interstellar medium is made up of gas and of this 75% is hydrogen. Small traces of Helium is also found. Hydrogen thus plays a major role in being an integral component. Gravity makes the matter stick together if there is no gravity we will simply end up in a universe with particles floating all over. We sure don't want that. All this composture sure doesn't happen in a single day, it takes almost 10 million years to form a star. We must add patience to the ingredients list. What is Nebula? A Nebula is an enormous cloud of gas and dust thrown out into space by dying stars. This gas and dust clump together they get bigger and bigger. Their gravity increases with their size. Ultimately, it grows enormous and collapses from its own gravity. The destruction causes the material at the core of the cloud to heat and this fiery core is the beginning of a star. Cold clouds form stars with lower mass. Giant clouds that are hotter form more massive stars. Stars also form in compact, dense clouds of gas and dust called Bok Globules (named after the scientist Bart J. Bok). We consider Bok Globules star-forming cocoons. What is a protostar? Protostars are very young stars at the earliest stage of their life cycle whose cores haven't formed yet. The gas cloud collapses towards the centre under gravity and builds a low mass protostar. A pancake looking disc of gas and dust surrounds the young star. It makes protostars hard to observe. Imagine a sunny side up egg, the yolk is surrounded by the egg white like a disk, similarly, the protostar is in the centre and the gas cloud surrounds it. The gas, dust and the other fragments in the disk continue to rain into it. The protostar enters pre-main sequence stage after all it dispenses the material in the disk. How are star clusters formed? The above process is how individual stars form, what about star clusters? How are they formed? The interstellar gas clouds remain under equilibrium until they attain a particular mass known as Jean's mass. Beyond that mass, the cloud collapses on itself because of the internal gravitational pull. Molecular clouds of extreme density collapse under gravity to form thousands of stars almost instantaneously. This event form star clusters. Events such as molecular clouds colliding with each other, nearby supernova explosions, galactic collisions can also result in star formation. Why is it important to learn about star formation? Our sun is a star we live deriving its energy. Learning about other star systems and their origins can help us trace out our own history. Planets form from particles in a disk of gas and dust, colliding and clinging together as they revolve around a Star. Earth took form the same way. Studying the origin of stars is almost same as looking at our own past. We are all made of star-stuff! Presentations are a great tool to simplify the content and communicate your message quickly, check out ours below.

How are stars formed?

science has blessed us with knowledge about them. Have you ever asked yourself what are these stars, anyway? How are they formed?

25 Oct 2020
"We are a way for the universe to know itself. Some part of our being knows this is where we came from. We long to return. And we can, because the cosmos is also within us. We are made of star-stuff," - Carl Sagan. Carl Sagan uttered above quote in his show "Cosmos" aired on PBS. Why did he say we are star-stuff? What did he mean? Did life on this planet jump out of stars and live on Earth one day? Of course not! All organic matter containing carbon formed in stars and got here through explosions called Nova. SuperNova is a stage in the life cycle of stars where massive ones explode billion times brighter than our Sun. We know how stars form from the giant molecular clouds called Nebula and how they sustain themselves through fission reaction. In this article, we deal with the life cycle of stars and all the stages involved. Mass of the stars determines their fate, larger the star shorter the lifespan. We measure the mass of stars, black holes, nebulae etc. using the unit Solar mass. One solar mass is approximately equal to the mass of our sun. On average, In Massive stars, that are many times larger than our Sun, the fusion reaction takes place at a faster rate. They exhaust their fuel faster and die early. Small-sized stars burn slowly. The fusion reaction takes place at a much slower rate. For Example, Stars about 40 solar masses live for a million years, while they estimate the smaller stars with almost one third the mass of our sun to live for 560 billion years (Our universe itself is 13.2 billion years old). Mind-blowing, Right?! Now let's jump right in. How are Protostars formed? The gas cloud collapses towards the centre under gravity and builds a low mass protostar. A pancake looking disc of gas and dust surrounds the young star. It makes protostars hard to observe. Imagine a sunny side up egg, the egg white surrounds the Yolk like a disk, in the same manner, the protostar is in the centre and the gas cloud surrounds it. The gas, dust and the other fragments in the disk continue to rain into it. The protostar enters pre-main sequence stage after all it dispenses the material in the disk. What are the Main-Sequence Stars? A main-sequence star is any star that fuses hydrogen to form helium in its core. Almost 90% of stars in the Universe including our sun, is a main-sequence star. Main-sequence stars attain stability, the energy released by the fission reaction keeps the star collapsing under its gravitational pull towards the core. For example, imagine blowing up a balloon while your friend is trying to crush it down. Nothing happens to the balloon when the air pressure you blow is equal to the compressing pressure, the same way the gravity wants to make the star collapse on itself while the nuclear fusion pushes the energy outwards. Main sequence stars attain stability between these two opposite forces. Red Giant Stage: At some point, in larger stars of the Main-sequence stage fuses all the hydrogen in its core, it leaves them with only helium. The core exhausts all the hydrogen fuel and leaves the star with only Helium. As it exhausts hydrogen in the core, the fusion reaction spreads outwards causing the star to expand 400 times its size. It swallows the nearby planets. Eventually, the hydrogen in the shell gets exhausted leaving the star with low temperatures and a faint reddish glow. This is the Red Giant phase and it can span around for a few thousand to 1 billion years. What happens to Low-mass stars? In case of Stars with mass up to 3 solar masses, the expansion during the Red giant phase continues till the star sheds its outer shells and the white core gets exposed. The core now exposed forms a White Dwarf. The outer shell shed by the star forms a planetary nebula. The Planetary Nebula is completely unrelated to planets or exoplanets but it is a layer of ionised gas that surrounds a dying star. White Dwarfs are roughly the size of Earth. Pressure from fast-moving electrons in the core keeps the star from collapsing any further. White dwarfs glow faintly with low energy and eventually cool down forming a Black Dwarf. Black Dwarves are dead stars. The following infographic explains the life of low-mass stars with pictures: What Happens to High-mass stars? Stars with core mass up to 8 solar masses die in a dramatic supernova that can shine billion times brighter than the sun. Note that in planetary Nebula only the shell of the star erupts but in a supernova, the entire star collapses including the core. Supernova can outshine entire galaxies space and can last for days to weeks. A rich array of subatomic particles and elements produced during these titanic explosions enrich the planets and star systems within their range. In our case, these supreme explosions made our planet optimal for survival. Dying stars gave us life that's the poetic nature of the Universe we live in! Massive stars that larger than 8 solar masses the core survives at the white dwarf stage and doesn't die down to form black dwarfs but the core continues to collapse. The inward pull of the core is so intense even the protons and electrons in the core combines to form neutrons. When all the protons and electrons in the star have combined, it becomes a Neutron star. Neutron stars are extremely dense as they have very high mass packed into a minuscule volume. They have powerful magnetic fields that speed up atomic particles present near its poles and this produces powerful beams called Pulsars which we can observe from the Earth. Stars with surviving core mass greater than 3 solar masses collapse to form a black hole. Black holes are infinitely dense objects with an infinite mass that can create a tear in the fabric of space-time. Nothing escapes their gravitational pull, not even light! The following mind map compares the life of Low-mass stars with high-mass stars: New star formation: The Nova and Super Nova that spread through the cosmos in the interstellar space form huge molecular clouds. These clouds act as stellar nurseries for a new generation of stars to form.

The Life cycle of Stars- A complete Guide

We try to understand every step in the life of a star from protostar formation to its death

24 Oct 2020
'Gravity' is a term you could have come across in and outside the boundaries of Physics. 'What is gravity?', this question among scientists has helped us understand the world with astounding precision but also pushed us further into mysteries over the past couple of centuries. Gravity is a pretty enormous topic of discussion, but here's what we will cover today for understanding its underlying nature. What is gravity? Why is understanding it so important? What is Newton's view of gravity? What is Einstein's theory of gravity? What is quantum gravity? And Getting into the weird part, we will talk about, Why does gravity bend light? Why does gravity slow-down time? And Why is gravity so weak? What is Gravity? Gravity is one of the four fundamental forces (gravity, electromagnetism, strong nuclear force, and weak nuclear force) of nature, it is the most fragile among the four, but that is all we know. We only know how gravity operates; we don't understand gravity itself (Yet!). It is crucial to understand gravity because if there is no gravity, we won't be here. We learned in star formation how gravity is necessary for holding stars together as they burn their insides out. There will be no stars, no planets, no moons, no us, and no pizza without gravity. Because there is a law such as gravity, the universe can and will create itself from nothing. -Stephen Hawking Newton's Gravity: Newton's gravitational law is a part of physics we are familiar with since elementary school. We all know the classic story of the apple falling on the great Isaac Newton's head, prompting him to the brilliant discovery. The apple part is bogus, but it is a fine story that helps you remember the events. Newton believed gravity is the force of attraction between two or more objects with mass. Everything exerts an attractive gravitational force on absolutely everything else. Gravity depends on the mass of the object and the distance between them. Newton's law, with great accuracy, explained the orbit of planets around stars and helped us put rockets in space, yet there is one significant problem. Newton did not explain what gravity is or how it transmits between two objects in space. To quote the genius himself, "It is inconceivable, that inanimate brute matter, should, without the mediation of something else, which is not material, operate upon and affect other matter without mutual contact. -Sir Isaac Newton's Mathematical Principle of Natural Philosophy and His System of the World. The man who discovered orbital mechanics and integral calculus might seem confused here; but then came Albert Einstein to the rescue. Einstein's view of gravity: The way we view the Universe changed when Einstein proposed his theory of Special relativity in 1905. Einstein took the great leap no one ever took before and declared gravity results from warping space-time. Wait, what do you mean by warping of space-time? What does that even mean? Let us go through this step by step! For understanding's sake, forget time and consider space. In the absence of any matter or energy space, it could be flat like the smooth surface of a table-when a massive body like the Sun emerges, it causes space to warp. It acts like a rubber sheet that curves when a bowling ball falls on it. A massive object (like the Sun) in space warps its surroundings; this affects other stuff (like planets) in its vicinity and forces them to follow a curved path. Einstein explained how gravity is nothing but a geometric consequence of curved space. The more massive the object, the more distortion it causes; more distortion means more gravity. Remember that Einstein's version of gravity is an upgraded view of Newton's gravity; in a way, both are correct. Einstein's space is poetic. It is not just a platform for events but a live arena that responds to matter and energy; it explains how gravity transmits from the Sun to earth through spatial distortion. Special relativity has led us to fascinating discoveries like the multi-dimensional view of space, black holes, gravitational waves, etcetera, yet our understanding of gravity remains incomplete. The problem is, the theory of relativity fails when it meets Quantum mechanics. To be precise, we do not know how gravity affects particles at the microscopic scale. Quantum Gravity: Quantum mechanics is a concept for understanding the microscopic properties of the Universe. Probing into quantum mechanics has led us to one conclusion so far; 'Understanding the familiar every day fails in the microscopic realm'. Nature offers us four fundamental forces. They are gravity, electromagnetism, and strong and weak nuclear forces. Among the four, three have a quantum description; that is- we know how they operate at subatomic levels. For example, consider a massive body like Jupiter; it is relatively easier to calculate how space curves around such a giant and its gravity. Now imagine an electron; how does such a microscopic particle curve space around it? It is not just hard to calculate; it is impossible as of now. Physicists also suggest that at quantum scales, gravitons exist. They are the hypothetical elementary particle that mediates the force of gravity. We haven't detected them, or we have no proof of their existence. Scientists are struggling to crack this problem and produce a unified theory of gravity that brings General relativity and Quantum mechanics together. Loop quantum gravity and string theory are strong candidates but lack experimental evidence. The answer to this problem will provide a much better understanding of reality itself; until then, May the force be with us! Gravity and its weirdness: Gravity has pretty wild tricks up its sleeve; it is not weird as we think it is. Gravity does not behave like the other forces we know well. Gravity is unique, and it has properties that we are just beginning to grasp; here is a few of them, Gravity slows time: Gravity not only warps space but also warps time; the stronger the gravitational field, the severe the warp. This effect has a mind-bending consequence called time-dilation. The closer you are to a massive object, the slower your time flows. For example, if your friend is living on Mount Everest and you are living in the mountain valley, your clock ticks slower than his clock because you are closer to the earth's gravitational field. It is the same reason gravity decreases with altitude. Dark matter Whenever scientists calculate the amount of gravity in the universe, there is always more than what there should be. That means we don't know where it comes from. We know gravity arises from the mass; we couldn't detect the actual matter; scientists call this unknown matter Dark matter. Dark matter does not interact with the electromagnetic force; therefore, it does not absorb, reflect or emit light, making it extremely hard to detect. In fact, researchers have been able to infer the existence of dark matter only from the gravitational effect it seems to have on visible matter. Dark matter seems to outweigh visible matter on a six to one ratio. For every one gram of visible matter, there are 6 grams of dark matter out there. The stuff we know and see (that makes up all stars and galaxies) only account for 5% of the universe's content! Scientists also suggest that dark matter is not some exotic matter; it's just our lack of understanding of gravity itself. Gravity bends light: We know mass and gravity go hand in hand, but how does gravity affect massless particles like photons? (Light is composed of elementary particles or packets of light called photons) The answer is, it doesn't directly affect light but distorts its path. When light travels from Sun to Earth, it doesn't travel in a straight line all the time. Massive planets (Mercury, Venus) interfere in their path and distort space around them; as the light passes through these distortions, it follows the curved path making it bent. Gravity is the weakest force: Gravity is the weakest among the four fundamental forces; we don't know why. It is 10^24 times weaker than weak nuclear force and 10^40 times weaker than electromagnetism. We call this the hierarchy problem in Physics. String theorists suggest gravity seems weak because it travels through extra dimensions in space; we haven't unleashed its full potential, again it leaves us with no proof. Gravity increases with density: Gravity not only increases with mass but also increases with density. Black holes are excellent examples of this phenomenon. When massive stars collapse on themselves, their mass becomes concentrated on a relatively smaller area and infinitely dense. These highly dense areas form black holes; they have an enormous gravitational pull that not even light can escape them! Thank you for joining us in this quest for understanding gravity. Subscribe to our weekly newsletter to get updates every time we post. Stay tuned for more!

What is gravity and why is it so weird?

It is crucial to understand gravity because if there is no Gravity, we won't be here. We learnt in star formation how gravity is necessary

24 Oct 2020