Astronomy

How was all the matter curled up inside a singularity during big bang ?

How was all the matter curled up inside a singularity during big bang ?


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If the singularity had infinite mass, temperature and density, then it should curve space and time but there was no space-time before big bang. So where did the singularity come to existence without space-time ?


There are multipble theories that could provide an answer to your question. One of them is that the universe is a quantum fluctuation that created forces, energy, etc… This would explain why we observe the total energy of the universe to be 0 (negative energy from repulsive gravity and positive energy from radiation, mass etc.). This theory is supported by alan guth's and Andrei Linde called inflation. http://en.wikipedia.org/wiki/Quantum_fluctuation http://en.wikipedia.org/wiki/Inflation_%28cosmology%29

Another theory called brane-theory, an idea that arose frome string theory which include multiverses etc., states that our universe was created in a collison between to branes. http://en.wikipedia.org/wiki/String_cosmology


The very short answer is "no one knows". The available evidence very strongly suggests that the Universe 13.8 billion years ago was hot, dense and expanding and the further back we look, the more indirect the clues we get are, but the hotter and denser it seems to have been.

There are multiple theories for what happens as we follow this process back and back, but theories is all they are. Scientists work to make testable predictions that would follow from some of them but not others, and allow us to whittle down the pool, but it's hard.

All that said, at the broadest level there seem to be two common current views as to how to address the question "what happened before the big bang".

One is to argue that it is simply a bad question: time, like space, is "curved" by the presence of a lot of mass or energy and the question may be analagous to asking "what is North of the North pole". There simnply is no "before" direction from "the Big Bang", or to put it another way, it is the nature of this universe to have a time dimension which only goes a finite distance in the "past" direction. This, very loosely, is the "no boundary" approach of Hawking and others.

The other view, which has names like "eternal inflation" or "cosmic inflation" is that the original state of the universe was a smooth and fairly featureless, but extremely rapidly expanding (exponentially rapidly) one, which was only meta-stable. Part or all of this universe, spontaneously "changed phase" to produce normal space and time, and as a result of the energy released by the phase change, was filled with very hot, very dense, matter and energy, still expanding, but no longer exponentially. Indeed, gravity then started to slow the expansion. In some theories just a small region would undergo this phase change, in others it would be the whole universe. Either way, all of the universe we see comes from a small region of the inflating universe.


Big Bang

The Big Bang theory is the prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent large-scale evolution. [1] [2] [3] The model describes how the universe expanded from an initial state of high density and temperature, [4] and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure.

Crucially, the theory is compatible with Hubble–Lemaître law — the observation that the farther away galaxies are, the faster they are moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity"). [5] Detailed measurements of the expansion rate of the universe place the Big Bang singularity at around 13.8 billion years ago, which is thus considered the age of the universe. [6]

After its initial expansion, an event that is by itself often called "the Big Bang", the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. Giant clouds of these primordial elements – mostly hydrogen, with some helium and lithium – later coalesced through gravity, forming early stars and galaxies, the descendants of which are visible today. Besides these primordial building materials, astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang theory and various observations indicate that this excess gravitational potential is not created by baryonic matter, such as normal atoms. Measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to dark energy's existence. [7]

Georges Lemaître first noted in 1927 that an expanding universe could be traced back in time to an originating single point, which he called the "primeval atom". Edwin Hubble confirmed through analysis of galactic redshifts in 1929 that galaxies are indeed drifting apart this is important observational evidence for an expanding universe. For several decades, the scientific community was divided between supporters of the Big Bang and the rival steady-state model which both offered explanations for the observed expansion, but the steady-state model stipulated an eternal universe in contrast to the Big Bang's finite age. In 1964, the CMB was discovered, which convinced many cosmologists that the steady-state theory was falsified, [8] since, unlike the steady-state theory, the hot Big Bang predicted a uniform background radiation throughout the universe caused by the high temperatures and densities in the distant past. A wide range of empirical evidence strongly favors the Big Bang, which is now essentially universally accepted. [9]


A Holographic Big Bang

Did the universe begin with a black hole in a higher-dimensional reality?

Depending on your level of cynicism, that question sounds like either an exciting idea or something you might hear from the stoner in your social circle. The reality: It’s a bit of interesting but speculative science from physicists attempting to solve a somewhat obscure problem in cosmology. Despite media coverage in Nature (later picked up by PBS and io9), the paper describing the research is unpublished and doesn’t correspond to existing observations. It’s still an interesting idea—one that can help us understand the study of our universe.

Over the past century, astronomers discovered that the universe is expanding. In the distant past, matter was compressed into a hot, opaque plasma with no stars. It expanded into what we see today, with the distance between galaxies growing larger with time. These observations and their theoretical description are known as the Big Bang model, a remarkably successful explanation for a wide variety of phenomena.

However, there’s a limit to our knowledge. Because the universe was opaque during its earliest times, we have only indirect information about what happened then. The more distant an object is from us, the farther back in time we’re seeing it, since light takes time to travel. We eventually reach a point where everything in the observed cosmos may have been compressed into a single point—but that’s not something we can see.

The infinite compression—called the Big Bang singularity—is problematic for many people, and for good reason. While infinity is fine in math, it causes some problems in physics, so a lot of researchers have tried to remove the singularity.

That’s the motivation for the recent paper by Razieh Pourhasan, Niayesh Afshordi, and Robert B. Mann. Their proposal begins with the hypothesis that our universe is actually embedded in a higher-dimensional reality, much as a photograph or (more appropriately) a hologram compresses three dimensions onto a two-dimensional surface. The force of gravity extends into the dimensions we can’t observe, but light and matter are confined to the four dimensions of space and time that we know.

This scheme, known as a braneworld, is not a new idea. (“Brane” is short for “membrane,” the concept being that our observable universe is a kind of membrane with other dimensions extending from it.) Braneworlds are a possible way to understand phenomena like the Big Bang singularity and also the acceleration of the universe, which is caused by a substance called dark energy. Fascinating as they are, though, braneworlds so far predict things that don’t gel with reality—faster-than-light particles or other pathological entities, for instance—or they otherwise fail to produce characteristics that fit with the observed Universe.

The new paper postulates that the Big Bang singularity is actually akin to a black hole in the braneworld scheme. A black hole—which is a well-studied and real type of object in our universe—consists of mass packed into a sufficiently small volume until it becomes so dense and has such a strong gravitational pull that it becomes surrounded by a boundary called an event horizon. Nothing falling past the event horizon can return to the outside universe, including light. The event horizon is what defines a black hole in any meaningful sense. The event horizon prevents us from directly observing a black hole’s singularity: the hypothetical point or ring at the center where all the mass is concentrated.

In the standard formulation, the Big Bang singularity has no event horizon, since it’s difficult to define an “inside” and “outside” when talking about the whole universe. However, in a braneworld the situation may be different. The authors of the new paper propose that a kind of higher-dimensional “star” collapsed to form an event horizon, just as high-mass stars die to form black holes, and that collapse produced our observable universe. According to this theory, the event horizon of the cosmos is a boundary beyond which we’re unable to observe, masking the Big Bang singularity from us. (As a bonus, this proposal solves many problems in other braneworld models.)

However, there’s a significant difficulty. As the authors themselves point out in the paper, their braneworld “white hole” model predicts a small but measurable fluctuation in the density of the Universe—and current observations from the Planck mission have already ruled out that possibility.

Even if a refined version of the braneworld white hole theory solves its immediate problem, it won’t overthrow the prevailing Big Bang model. The confusion lies in the language we use. The term “Big Bang model” describes an extensive set of observations—including the way galaxies are moving apart the light left over from when the universe became transparent and the relative number of hydrogen, helium, and lithium atoms—yet the term is also used to describe the initial singularity. However, that singularity is not essential to the Big Bang model.

No matter how cool it sounds, the braneworld white hole model has a set of challenges before it can be considered a viable explanation for the very early universe. The theory was formulated to solve a problem in braneworld cosmology, which itself may or may not be a meaningful model.

More than that: as with all theories, the braneworld white hole must agree with the existing data, which it currently doesn’t do. The fact that the authors recognize the problem is a credit to them. Exciting ideas must be compatible with observation and experiment, and all scientific theories should be considered provisional, constantly tested by evidence. If the authors can’t reconcile their model with the data, the theory will join many others that seem exciting at first but don’t turn out to correspond to reality.


What Happened During the Big Bang?

The Big Bang. That incredible, cosmic moment that led to everything we see and everything we know today. When the theory was first suggested, it seemed outlandish. Impossible. Insane. But when it comes to the universe, what seems crazy is often true. We understand the overarching concept of the Big Bang, but what exactly happened? Here’s what we know (or suspect) about the first moments of the Big Bang, 13.7 billion years ago:

1. First, there was nothing. Then, there was a singularity.
The question of what came before the Big Bang is both frustrating and futile. There was nothing, according to the theory, so there was no “before”. It came about suddenly, instantaneously. First, nothing. Then, a singularity, or something very close to a singularity, which is an infinitely small point, arose. This singularity is what “experienced” the Big Bang. It contained everything, all the mass and all the space-time that would be ejected out in the next phase.

2. In one big rush of inflation, the universe expanded.
The reason we call it the Big Bang is due to the main event, inflation. In a single moment, the singularity expanded rapidly at a rate that we believe was faster than the speed of light. Space-time itself was expanding, and suddenly all the mass contained within the singularity was released and began to expand as well.

The theory suggests that the original matter was actually dark energy, which then converted into ordinary matter. This conversion, which we call reheating, made the existing universe very hot. All this heat gave rise to a quark-gluon plasma. These extreme temperatures didn’t last forever, though.

3. Plasma cools, leaving protons and neutrons to form.
As the universe began to cool, elementary particles that had been freely shooting around in the energetic universe were finally able to combine to form protons and neutrons. Many of these protons and neutrons then combined into deuterium and helium, but most of the protons hung around by themselves to remain as hydrogen nuclei. Eventually, the hydrogen and helium began to collect electrons, which had been moving too quickly to be combined before that point. Once these particles were combined, photons could more easily move about.

There’s a lot more to know about the Big Bang, of course, but this simplistic overview gives a general image of what we know, and how we can explain what we see today.

Concise here and easy to read and follow. I note about point 2 "The reason we call it the Big Bang is due to the main event, inflation"

Inflation was never part of the original, standard Big Bang model (go back to George Gamow and Ralph Alpher in late 1940s). It was developed by Alan Guth et al to answer the horizon-problem in the Big Bang model. Energy and information can only exchange at velocity c so the origin of the cosmic microwave background would be very lumpy all over as the universe expanded and not smooth as observed today. The standard Big Bang model has a light-travel-time issue in the model that inflation seeks to answer - as well as find a way out of the *singularity* in the beginning

Truthseeker007

Voidpotentialenergy

Maybe a neighbor universe collided with our universe size black hole that started the expansion.
At some point we will run into our neighbors and begin to contract.
Each universe started from (nothing) just potential energy of void space.
Over colossal lengths of time each one grew.
Will and has happened forever.

No singularity and magical appearance needed.
All JMO

Maybe a neighbor universe collided with our universe size black hole that started the expansion.
At some point we will run into our neighbors and begin to contract.
Each universe started from (nothing) just potential energy of void space.
Over colossal lengths of time each one grew.
Will and has happened forever.

No singularity and magical appearance needed.
All JMO

Voidpotentialenergy

Standard thinking was made to be broken.
Almost a guarantee that everything taught in physics will be wrong and continue to be wrong.

At best the brightest minds of today won't be right.
All just best guess work.

Standard thinking was made to be broken.
Almost a guarantee that everything taught in physics will be wrong and continue to be wrong.

At best the brightest minds of today won't be right.
All just best guess work.

Voidpotentialenergy

IMO we live in a black hole in expansion phase.
And reason everything looks flat projector like.

Like i said everyone is probably wrong so take it for what its worth.

Truthseeker007

Well as far as I know Quantum Physics is finding some interesting things. And if it isn't an infinite number of universes I think more then likely their is more then one. Yea I know we are just finding planets we didn't know about in this massive universe but I like to think outside the box.

Ponder this: What is at the end of this Universe? I know they have seen the end but if you were to fly to the end of this universe would it be kind of like what happens when you leave a planet? Also if you could fly through a black hole would that be like a wormhole to another universe?

I don't claim to be an expert on this at all but I do like to ponder on this. I do believe in the future we will find that this is not the only universe. And what about even parallel universes that are like this but a little different ?Such as their is still and earth in a parallel dimension but maybe in the parallel one earth has more land and less ocean.

Truthseeker007

Well as far as I know Quantum Physics is finding some interesting things. And if it isn't an infinite number of universes I think more then likely their is more then one. Yea I know we are just finding planets we didn't know about in this massive universe but I like to think outside the box.

Ponder this: What is at the end of this Universe? I know they have seen the end but if you were to fly to the end of this universe would it be kind of like what happens when you leave a planet? Also if you could fly through a black hole would that be like a wormhole to another universe?

I don't claim to be an expert on this at all but I do like to ponder on this. I do believe in the future we will find that this is not the only universe. And what about even parallel universes that are like this but a little different ?Such as their is still and earth in a parallel dimension but maybe in the parallel one earth has more land and less ocean.

Given some of your comments here, I think you may enjoy this book, if you do not already have it. *Black Holes & Time Warps Einstein's Outrageous Legacy* by Kip S. Thorne, forward by Stephen Hawking. My copy is from 1994. This book talks about quantum gravity and that quantum gravity used to model the Big Bang and black holes - is not well understood. Unlike Kepler's planetary laws, Newton's laws of motion, gravity, etc. those laws are defined by math and tested now for several centuries. I have never seen quantum physics or mechanics applied to model the motion of the Galilean moons at Jupiter and publish a QM ephemeris table for astronomy to use to view and test Galilean moon events at Jupiter and what telescope users on Earth should see along with the time of these events too. In fact, I have not seen a QM electron gazer's almanac published for 2020 like I have for upcoming celestial events viewable published by Sky & Telescope magazine. My point - quantum physics has its domain but not perhaps, an unlimited domain and application for everything we see today in nature, macro astronomical celestial events like the Galilean moons and motion looks like one of those areas and is better modeled and explained using old school astronomy

When it comes to other dimensions and parallel universes or other worlds in quantum thinking, last night I was out viewing Auriga constellation using my telescope and enjoyed views of four, open clusters. NGC 1857, M38, M36, and M37 in Auriga. I could plainly see the Earth is rotating in the field of view (the angular velocity rate across the field of view), however, I did not see any other universes peering back at me using my telescope

Voidpotentialenergy

Well as far as I know Quantum Physics is finding some interesting things. And if it isn't an infinite number of universes I think more then likely their is more then one. Yea I know we are just finding planets we didn't know about in this massive universe but I like to think outside the box.

Ponder this: What is at the end of this Universe? I know they have seen the end but if you were to fly to the end of this universe would it be kind of like what happens when you leave a planet? Also if you could fly through a black hole would that be like a wormhole to another universe?

I don't claim to be an expert on this at all but I do like to ponder on this. I do believe in the future we will find that this is not the only universe. And what about even parallel universes that are like this but a little different ?Such as their is still and earth in a parallel dimension but maybe in the parallel one earth has more land and less ocean.

Voidpotentialenergy

I always wondered if we are just 1 of an infinite number of universes are we part of a galaxy of universes.

Infinite regression.
Make some seance that if it goes on forever a structure would appear in the forever .

Truthseeker007

Given some of your comments here, I think you may enjoy this book, if you do not already have it. *Black Holes & Time Warps Einstein's Outrageous Legacy* by Kip S. Thorne, forward by Stephen Hawking. My copy is from 1994. This book talks about quantum gravity and that quantum gravity used to model the Big Bang and black holes - is not well understood. Unlike Kepler's planetary laws, Newton's laws of motion, gravity, etc. those laws are defined by math and tested now for several centuries. I have never seen quantum physics or mechanics applied to model the motion of the Galilean moons at Jupiter and publish a QM ephemeris table for astronomy to use to view and test Galilean moon events at Jupiter and what telescope users on Earth should see along with the time of these events too. In fact, I have not seen a QM electron gazer's almanac published for 2020 like I have for upcoming celestial events viewable published by Sky & Telescope magazine. My point - quantum physics has its domain but not perhaps, an unlimited domain and application for everything we see today in nature, macro astronomical celestial events like the Galilean moons and motion looks like one of those areas and is better modeled and explained using old school astronomy

When it comes to other dimensions and parallel universes or other worlds in quantum thinking, last night I was out viewing Auriga constellation using my telescope and enjoyed views of four, open clusters. NGC 1857, M38, M36, and M37 in Auriga. I could plainly see the Earth is rotating in the field of view (the angular velocity rate across the field of view), however, I did not see any other universes peering back at me using my telescope

I do love reading so thanks for the tip on the book. It does sound very interesting. Have you ever heard of exopolitics? You seem very intelligent so I am sure you have. Here is an interesting link for you to check out if you get time. https://www.exopolitics.org/

Wow! You must have a pretty awesome telescope! Are you able to take pictures of what you see through it? That is really neat. I am pretty sure you wouldn't be able to see other universes or dimensions with the naked eye. After all isn't the universe roughly 68% dark energy. Yes we don't know what it is exactly but I have my theories. Lol!

I do love reading so thanks for the tip on the book. It does sound very interesting. Have you ever heard of exopolitics? You seem very intelligent so I am sure you have. Here is an interesting link for you to check out if you get time. https://www.exopolitics.org/

Wow! You must have a pretty awesome telescope! Are you able to take pictures of what you see through it? That is really neat. I am pretty sure you wouldn't be able to see other universes or dimensions with the naked eye. After all isn't the universe roughly 68% dark energy. Yes we don't know what it is exactly but I have my theories. Lol!

Truthseeker007

Truthseeker007

I always wondered if we are just 1 of an infinite number of universes are we part of a galaxy of universes.

Infinite regression.
Make some seance that if it goes on forever a structure would appear in the forever .

Truthseeker007

I think the whole flat earth theory was some kind of psyops created by something such as the CIA to see how gulliable people can be. But I don't know for sure but clearly it is a fact our Earth and the Sun and all the other planets are round. But hey to each their own I guess. I mean many people are gullible enough to think some Jesus is coming back to save them.

I had a telescope at one point but it wasn't very good or worth even using. I am guessing you have to spend in the 1,000 dollar range to get anything worth looking into.

I think the whole flat earth theory was some kind of psyops created by something such as the CIA to see how gulliable people can be. But I don't know for sure but clearly it is a fact our Earth and the Sun and all the other planets are round. But hey to each their own I guess. I mean many people are gullible enough to think some Jesus is coming back to save them.

I had a telescope at one point but it wasn't very good or worth even using. I am guessing you have to spend in the 1,000 dollar range to get anything worth looking into.

Truthseeker007

David-J-Franks

Steady State of The Infinite: Time Free will Randomness Cause and effect Information and order Black holes Big bang: Franks, David J: 9781098852924: Amazon.com: Books

Steady State of The Infinite: Time Free will Randomness Cause and effect Information and order Black holes Big bang: Franks, David J: 9781098852924: Amazon.com: Books

David-J-Franks, you are correct about the multiverse and a fingerprint in the CMBR. My telescopes cannot see detail like this in the CMBR, I enjoy optical light viewing in the eyepieces. I have not seen anything on this topic since the Dec 2012 Sky & Telescope magazine. This is a quick summary of the S&T report, 'Cosmic Collisions' in the December 2012 issue which reviewed the multiverse or bubble cosmology. Efforts are underway in cosmology to establish that the big bang is part of an eternal inflating universe which during the early inflation period, about 10^-35 second after the big bang, some bubbles collided with our universe and left behind fingerprints in the cosmic microwave background radiation or CMBR that point to other universes and bubbles in cosmology. These bubble fingerprints could support that the universe is just part of a grand multiverse that is eternal and according to string theory, perhaps 10^500 different universes exist (p. 23). Cosmologists are studying intently WMAP data and waiting for results from the European Space Agency Planck spacecraft measurements to look for evidence of past colliding bubbles in the CMBR. Some problems were discussed in the big bang model that inflation solves like the missing magnetic monopoles, uniformity of space in all directions and the flatness problem of the universe. The largest conflict between calculation and observation was discussed, namely dark energy influence should be > 10^100 than observations allow. This is considered to be the largest discrepancy between theory and observation in science. However the multiverse using string theory could solve this. As the report stated – “String theory could solve this problem if multiple universes exist. The theory implies the existence of 10^500 different types of empty space, with different particles, forces, and amounts of dark energy allowed in each, Guth explains. If instead of just one, every one of these 10^500 possible solutions is correct – meaning each solution matches a different universe that exists in a larger multiverse – then dark energy’s value isn’t weird at all. We just live in one of the universes where the amount of dark energy is what we measure it to be, a value particularly friendly to our existence. These theoretical arguments do not constitute direct evidence for multiple universes. But such evidence might be found. The infinite, higher-dimensional multiverse (the cheese in the Swiss cheese) into which these bubble universes are born would expand faster than any of its individual bubbles, but if enough universes popped into being in this landscape, some of them might form close enough to collide with our own. This collision could leave a temperature bruise in the CMB’s mottled surface shaped like a faint, round disk. Such a disk would consist of photons that are slightly warmer (or cooler) than the surrounding CMB, anomalies that are even weaker than those that show up in the iconic map from NASA’s Wilkinson Microwave Anisotropy Probe (WMAP). That’s saying something, because the CMB’s 2.7-kelvin temperature deviates by at most 0.0002 kelvin from one point to another across the entire sky.” – page 23., ref - Cosmic Collisions, Sky & Telescope 124(6):20-26, 2012 (December)

When I view galaxies like M31, M33, and others, I have very good views using my 10-inch telescope and cannot observe anomalies in the CMBR. According to the Big Bang model and especially inflation theory, there is an immense space beyond the CMBR but telescopes do not observe this universe When George Gamow and Ralph Alpher developed the Big Bang in the late 1940s, the background radiation was supposed to be some 50 kelvin degrees and very lumpy that would be seen, not smooth and near 3 kelvin degrees. The cosmology department went to work explaining what was found in the 1960s, now we have inflation and the multiverse For me, I can see M31, M33, etc. but no multiverse


Mind-Bending Study Suggests Time Did Actually Exist Before The Big Bang

According to a straightforward interpretation of general relativity, the Big Bang wasn't the start of 'everything'.

Taking Einstein's famous equations at face value and making as few assumptions as possible, a team of researchers has rewound the clock on our Universe to find it wouldn't lead to a stopping point at all, but would take us through a different kind of beginning into a flipped space.

To understand what all the fuss over the Big Bang is, we need to rewind a bit to understand why physicists think it may not have been the start of everything.

Around 90 years ago, a Belgian astronomer named Georges Lemaître proposed that observed changes in the shifting of light from distant galaxies implied the Universe is expanding. If it's getting bigger, it stands that it used to be smaller.

Keep rewinding the clock – by around 13.8 billion years – and we get to a point where space has to be confined to an incredibly tiny volume, also known as a singularity.

"At this time, the Big Bang, all the matter in the universe, would have been on top of itself. The density would have been infinite," Stephen Hawking once explained in his lecture on The Beginning of Time.

There are a number of models physicists use to describe the nothingness of empty space. Einstein's general relativity is one - it describes gravity as it relates to the geometry of the Universe's underlying fabric.

Theorems proposed by Hawking and mathematician Roger Penrose claim that solutions to general relativity's equations on an infinitely constrained scale – like the one inside a singularity – are incomplete.

In everyday terms, it's often said physics breaks down at the singularity, leading to a mix of speculations on what little we can tease out of the physics that still makes sense.

Hawking only recently gave his own take in an interview with Neil deGrasse Tyson, where he likened the space-time dimensions of the Big Bang to the South Pole. "There is nothing south of the South Pole, so there was nothing around before the Big Bang," he said.

But other physicists have argued there's something beyond the Big Bang. Some propose that there is a mirror Universe on the other side, where time moves backwards. Others argue in favour of a rebounding Universe.

Taking a slightly different approach, physicists Tim A. Koslowski, Flavio Mercati, and David Sloan have come up with a new model, pointing out that the breakdown arises from a contradiction in properties at a particular point in time as defined by general relativity.

What the theorem doesn't imply is how the Universe as we observe it necessarily gets to that point in the first place.

Stepping back from the whole singularity issue, the researchers reinterpreted the existing model of shrinking space by distinguishing the map of space-time itself from the 'stuff' in it.

"All the terms that are problematic turn out to be irrelevant when working out the behaviour of quantities that determine how the Universe appears from the inside," said Sloan, a physicist from the University of Oxford.

What this essentially adds up to is a description of the Big Bang where physics remains intact as the stage it acts upon reorientates.

Rather than a singularity, the team call this a Janus Point, named after the Roman god with two faces.

The relative positions and scales of the stuff that makes up the Universe effectively flatten into a two-dimensional pancake as we rewind time. Passing through the Janus Point, that pancake turns 3D again, only back-to-front.

What that means in physical terms is hard to say, but the researchers believe it could have profound implications on symmetry in particle physics, maybe even producing a Universe based primarily on antimatter.

While the idea of a flipped Universe is old news, the approach of working around the singularity problem in this particular way is novel.

"We introduce no new principles, and make no modifications to Einstein's theory of general relativity – only of the interpretation that is put upon objects," said Sloan.

No doubt this debate will rage on well into the future. Who knows? Maybe there's a similar argument happening in the mirror Universe sometime on the other side of the Janus Point.


Big Bang query: Mapping how a mysterious liquid became all matter

The leading theory about how the universe began is the Big Bang, which says that 14 billion years ago the universe existed as a singularity, a one-dimensional point, with a vast array of fundamental particles contained within it. Extremely high heat and energy caused it to inflate and then expand into the cosmos as we know it -- and, the expansion continues to this day.

The initial result of the Big Bang was an intensely hot and energetic liquid that existed for mere microseconds that was around 10 billion degrees Fahrenheit (5.5 billion Celsius). This liquid contained nothing less than the building blocks of all matter. As the universe cooled, the particles decayed or combined giving rise to. well, everything.

Quark-gluon plasma (QGP) is the name for this mysterious substance so called because it was made up of quarks -- the fundamental particles -- and gluons, which physicist Rosi J. Reed describes as "what quarks use to talk to each other."

Scientists like Reed, an assistant professor in Lehigh University's Department of Physics whose research includes experimental high-energy physics, cannot go back in time to study how the Universe began. So they re-create the circumstances, by colliding heavy ions, such as Gold, at nearly the speed of light, generating an environment that is 100,000 times hotter than the interior of the sun. The collision mimics how quark-gluon plasma became matter after the Big Bang, but in reverse: the heat melts the ions' protons and neutrons, releasing the quarks and gluons hidden inside them.

There are currently only two operational accelerators in the world capable of colliding heavy ions -- and only one in the U.S.: Brookhaven National Lab's Relativistic Heavy Ion Collider (RHIC). It is about a three-hour drive from Lehigh, in Long Island, New York.

Reed is part of the STAR Collaboration , an international group of scientists and engineers running experiments on the Solenoidal Tracker at RHIC (STAR). The STAR detector is massive and is actually made up of many detectors. It is as large as a house and weighs 1,200 tons. STAR's specialty is tracking the thousands of particles produced by each ion collision at RHIC in search of the signatures of quark-gluon plasma.

"When running experiments there are two 'knobs' we can change: the species -- such as gold on gold or proton on proton -- and the collision energy," says Reed. "We can accelerate the ions differently to achieve different energy-to-mass ratio."

Using the various STAR detectors, the team collides ions at different collision energies. The goal is to map quark-gluon plasma's phase diagram, or the different points of transition as the material changes under varying pressure and temperature conditions. Mapping quark-gluon plasma's phase diagram is also mapping the nuclear strong force, otherwise known as Quantum Chromodynamics (QCD), which is the force that holds positively charged protons together.

"There are a bunch of protons and neutrons in the center of an ion," explains Reed. "These are positively charged and should repel, but there's a 'strong force' that keeps them together -- strong enough to overcome their tendency to come apart."

Understanding quark-gluon plasma's phase diagram, and the location and existence of the phase transition between the plasma and normal matter is of fundamental importance, says Reed.

"It's a unique opportunity to learn how one of the four fundamental forces of nature operates at temperature and energy densities similar to those that existed only microseconds after the Big Bang," says Reed.

Upgrading the RHIC detectors to better map the "strong force"

The STAR team uses a Beam Energy Scan (BES) to do the phase transition mapping. During the first part of the project, known as BES-I, the team collected observable evidence with "intriguing results." Reed presented these results at the 5th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan in Hawaii in October 2018 in a talk titled: "Testing the quark-gluon plasma limits with energy and species scans at RHIC."

However, limited statistics, acceptance, and poor event plane resolution did not allow firm conclusions for a discovery. The second phase of the project, known as BES-II, is going forward and includes an improvement that Reed is working on with STAR team members: an upgrade of the Event Plan Detector. Collaborators include scientists at Brookhaven as well as at Ohio State University.

The STAR team plans to continue to run experiments and collect data in 2019 and 2020, using the new Event Plan Detector. According to Reed, the new detector is designed to precisely locate where the collision happens and will help characterize the collision, specifically how "head on" it is.

"It will also help improve the measurement capabilities of all the other detectors," says Reed.

The STAR collaboration expects to run their next experiments at RHIC in March 2019.

In addition to her involvement in STAR, Reed is also part of the sPHENIX Collaboration which will build a new detector at Brookhaven, which is anticipated to begin running in 2023.

The material Reed presented at the conference is based upon work supported by the National Science Foundation under Grant No. 1614474.


Definitioner

In a general sense: Collective name for all phenomena in which energy is transported through space in the form of waves or particles. In a more restricted sense, the word is often used synonymously with electromagnetic radiation.

quantum gravity Theory based both on the effects, concepts and laws of quantum theory and on those of general relativity. To date, no complete such theory exists the best-known candidate theories are string theory and loop quantum gravity. Some information on the question of quantum gravity can be found in the chapter Relativity and the quantum of Elementary Einstein, starting with the page Border regions of gravity. Selected aspects of quantum gravity are described in the category Relativity and the quantum of our Spotlights on relativity. point Elementary "building block" of geometrical entities such as surfaces or more general spaces. For instance, a surface is the set of all its points, of all possible locations on the surface, and all geometrical objects in that surface are defined by the points that belong to them - for instance, a line on the surface is the set of (infinitely many) points. planet Planets are not-too-small companions of a star that are not stars themselves (nor ever were stars). In our solar system, the planets are, listed from the one closest to the sun to the one farthest: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. As of August 2006, Pluto, which used to be a proper planet, is officially a "dwarf planet". In the night sky, the distinguishing characteristic of planets is that they move around relative to the unchanging background of stars - which gave them their name, loosely translated from Greek as "wanderers". matter In general relativity: All contents of spacetime that contribute to its curvature: particles, dust, gases, fluids, electromagnetic and other fields. In particle physics: All elementary particles with half-integer spin, such as electrons and quarks, as well as their composites such as protons and neutrons, in contrast with force particles. mass In classical physics, mass plays a triple role. First of all, it is a measure for how easy it is to influence the motion of a body. Imagine that you're drifting in emtpy space. Drifting by are an elephant and a mouse, and you give each of them a push of equal strength. The fact that the mouse abruptly changes its path, while the elephant's course is as good as unaltered, is a sure sign that the mass (or, in the language of physics, the inertia or inertial mass) of the elephant is much greater than that of the mouse. Secondly, mass is a measure of how many atoms there are in a body, and of what type they are. All atoms of one and the same type have the same mass, and adding up all those tiny component masses, the total mass of the body results. Thirdly, in Newton's theory of gravity, mass determines how strongly a body attracts other bodies via the gravitational force, and how strongly these bodies attract it (in this sense, mass is the charge associated with the gravitational force). In special relativity, one can also define a mass that is a measure for a bodies resistance to changing its motion. However, the value of this relativistic mass depends on the relative motion of the body and the observer. The relativistic mass is the "m" in Einstein's famous E=mc² (cf. equivalence of mass and energy). The relativistic mass has a minimum for an observer that is at rest relative to the body in question. This value is the so-called rest mass of the body, and when particle physicists talk of mass, this is usually what they mean. Just as in classical physics, the rest mass is a kind of measure for how much matter the body is made up of - with one caveat: For composite bodies, the energies associated with the forces holding the body together contribute to the total mass, as well (another consequence of the equivalence of mass and energy). In general relativity, mass still plays a role as a source of gravity however, it has been joined by physical quantities such as energy, momentum and pressure. light Light in the strict sense of the word is electromagnetic radiation the human eye can detect, with wave-lengths between 400 and 700 nanometres. In relativity theory and in astronomy, the word is often used in a more general sense, encompassing all kinds of electromagnetic radiation. For instance, astronomers might talk about "infrared light" or "gamma light" in this context, light in the stricter sense is referred to as "visible light". Within classical physics, the properties of light are governed by Maxwell's equations in quantum physics, it turns out that light is a stream of energy packets called light quanta or photons. In the context of relativistic physics, light is of great interest, and for a number of reasons. First of all, the speed of light plays a central role in both special and general relativity. Also, there are a number of interesting effects in general relativity which are associated with the propagation of light, namely deflection, the Shapiro effect and the gravitational redshift. light elements According to the big bang models, the early universe underwent a brief period of primordial nucleosynthesis between a few seconds and a few minutes cosmic time, during which nuclei of light elements such as heavy hydrogen, helium and lithium formed. A brief account of this Big Bang Nucleosynthesis can be found in the spotlight text Big Bang Nucleosynthesis, while Equilibrium and change provides more information about the physical processes involved and Elements of the past describes how the predictions of Big Bang Nucleosynthesis can be tested against astronomical observation. inflation

Hypothetical phase in the earliest universe during which the cosmos underwent exponentially growing expansion.

helium After hydrogen, the second lightest chemical element. Its atomic nucleus consists of two protons and, ordinarily, two neutrons ("helium-4") such helium nuclei are also called alpha particles. Another variety of helium, helium-3, has only one neutron in its nucleus. In the context of general relativity, both helium-3 and helium-4 are is of interest as two species of light atomic nuclei that formed in the early universe during Big Bang Nucleosynthesis. gravity See gravitation gravity (gravitation) In classical physics: An action-at-a-distance force by which all bodies that possess mass attract each other (see Newtonian theory of gravity), synonym: gravitational force. In Einstein's general theory of relativity: The fact that matter that possesses mass, energy, pressure or similar properties distorts spacetime, and that this distortion in turn influences whatever matter might be present. An introduction to the basic ideas of general relativity is provided by the section General relativity of Elementary Einstein. More information about the nature of gravity in general relativity can be found in the spotlight text Gravity: From weightlessness to curvature. geometry That part of mathematics concerning itself with surfaces or more general spaces as well as objects defined on such spaces, such as points or lines as well as the objects constructable from points and lines, such as triangles. general relativity (general theory of relativity) Albert Einstein's theory of gravity a generalization of his special theory of relativity. For information about the concepts and applications of this theory, we recommend the chapter general relativity of our introductory section Elementary Einstein. Further information about many different aspects of general relativity and its applications can be found in our section Spotlights on relativity. gas In a strict sense: A state of matter in which the atoms and/or molecules wildly careen and collide, without being bound to each other. This movement leads to an inner pressure, while the average kinetic energy of the moving particles is a measure for the temperature of the gas. Compare the other states of matter: solid state, liquid, plasma. In a broader sense, gas is also used to denote other mixtures of freely careening particles, for instance in the case of the electron gas whose pressure stabilizes a white dwarf against further collapse. galaxy Stars are rarely found alone - usually, they congregate in conglomerates of millions, billions or even more stars called galaxies. A case in point is our sun, part of a galaxy we call the milky way. The life of a young galaxy can be very turbulent. Examples of such young, active galactic nuclei are radio galaxies and quasars. energy Physical quantity with the special property that, in physical processes, energy is neither destroyed nor created, simply transformed from one form of energy to another. Some of the different forms of energy that are defined separately are kinetic energy, thermal energy and the energy carried by electromagnetic radiation. Processes that transform one form of energy into another take place in all machines we use in everyday life, from the engine of a subway train (electrical energy into kinetic energy of the train) to an electric blanket (electrical energy into thermal energy). One important consequence of special relativity is that energy and mass are completely equivalent - two different ways to define what is, on closer inspection, one and the same physical quantity. See the keyword equivalence between mass and energy. density In a stricter sense synonymous with "mass density": The average density of matter in a region of space is the total mass of all matter contained in that region, divided by the region's volume. More generally, density can refer to other physical quantities as well. The energy density, for instance, is the total sum of energy localized in a region divided by that region's volume. curvature For a two-dimensional surface: criterion that allows us to decide whether that surface is a plane, or part of a plane (i.e. a surface on which the usual rules of high school geometry apply), or not. Two possibilities to define the curvature of a plane are the following: Sum of the angles of a triangle. In a plane, the sum of the three angles in a triangle formed by three straight lines is always 180 degrees. In a more general surface, the sum of the angles of a more general triangle formed by three straightest-possible lines (i.e. geodesics) can be larger or smaller than 180 degrees. The difference (the surplus or deficit), divided by the area of the triangle, is a measure for the curvature of that region of the surface. Second possibility: the circumference of a circle. In the plane, that circumference is equal to 2 times pi times the circle's radius. On a more general surface, it can be larger or smaller. The difference, divided by the third power of the radius, leads to the same measure for the curvature as the first definition. Simple examples for curved surfaces are the surface of a sphere (positive curvature, that is to say: sum of the angles in a triangle larger than 180 degrees, circumference of a circle smaller than 2 times pi times radius) and that of a saddle (negative curvature, that is to say: sum of the angles in a triangle smaller than 180 degrees, circumference of a circle larger than 2 times pi times radius). Curvature cannot only be defined for surfaces, but also for higher-dimensional, more general spaces or spacetimes. However, the generalized definition is substantially more complicated, and curvature is defined not by a single number, but by a set of numbers (that, together, form the "curvature tensor"). It's basic meaning, however, is the same: it measures the space's deviation from a flat space of the same dimension. For physics, an important aspect of curvature is its connection with gravity, as described in Einstein's general theory of relativity. Basic information about this can be found in the spotlight text Gravity: From weightlessness to curvature. current

Matter in coordinated, flowing motion - think of water flowing in a pipe. An important example is the electric current associated with moving electric charges. Electric currents are the sources of magnetic fields.


Relics of the Big Bang –“Dark Matter is Composed of Primordial Black Holes”

“Ancient black holes would give us access to physics we would never otherwise be able to do,” wrote Dan Hooper , head of the theoretical astrophysics group at Fermilab, in an email to The Daily Galaxy. If primordial black holes are real, they’d have potential to solve a whole host of the biggest problems in cosmology, not the least being the mystery of dark matter, considered to be the backbone to the structure of the universe.

The First Second after the Big Bang

“If these black holes were initially lighter than a million kilograms or so,” Hooper added, “they would have evaporated in the first second after the Big Bang. In the process of this evaporation, they could have created any number of exotic forms of matter and energy, including dark matter.”

“But it is also undeniable that we are profoundly puzzled, especially when it comes to the first fraction of a second that followed the Big Bang,” Hooper adds . “I have no doubt that these earliest moments hold incredible secrets, but our universe holds its secrets closely. It is up to us to coax those secrets from its grip, transforming them from mystery into discovery.”

Primordial black holes (PBHs) could account for all or part of dark matter, be responsible for some of the observed gravitational waves signals, and seed supermassive black holes found in the center of our Galaxy and other galaxies, reports the Kavli Institute for the Physics and Mathematics of the Universe .

Intriguing PBH Candidate Event

The first observations of the Hyper Suprime-Cam (HSC) of the 8.2m Subaru Telescope, a gigantic digital camera near the 4,200 meter summit of Mt. Mauna Kea in Hawaii, have already reported a very intriguing candidate event consistent with a PBH from the “multiverse,” with a black hole mass comparable to the mass of the Moon. Encouraged by this first sign, and guided by the new theoretical understanding, the team is conducting a new round of observations to extend the search and to provide a definitive test of whether PBHs from the multiverse scenario can account for all dark matter.

PBH’s could also play a role in the synthesis of heavy elements when they collide with neutron stars and destroy them, releasing neutron-rich material, reports the Kavli Institute. “In particular, there is an exciting possibility that the mysterious dark matter, which accounts for most of the matter in the universe, is composed of primordial black holes.”

Existence of Black holes Confirmed –Enter PHBs

The 2020 Nobel Prize in physics was awarded to a theorist, Roger Penrose, and two astronomers, Reinhard Genzel and Andrea Ghez, for their discoveries that confirmed the existence of black holes. Since black holes are known to exist in nature, contradicting Albert Einstein who believed that they “did not exist in the real world,” nor that a fathomless dark creation existed at the very real, violent center of our home galaxy.

In January 1965, ten years after Einstein’s death, Penrose proved that black holes really can form and described them in detail at their heart, black holes hide a singularity in which all the known laws of nature cease. His groundbreaking theory is still regarded as the most important contribution to the general theory of relativity since Einstein.

Their existence proven, says the Kavli Institute, PHBs make a very appealing candidate for dark matter. The recent progress in fundamental theory, astrophysics, and astronomical observations in search of PBHs has been made by an international team of particle physicists, cosmologists and astronomers, including Kavli IPMU members Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada and Volodymyr Takhistov.

To learn more about primordial black holes, the research team looked at the early universe for clues. The early universe was so dense that any positive density fluctuation of more than 50 percent would create a black hole. However, cosmological perturbations that seeded galaxies are known to be much smaller. Nevertheless, a number of processes in the early universe could have created the right conditions for the black holes to form.

PHBs Form Baby Universes

One exciting possibility, suggests the Kavli Institute, is that primordial black holes could form from the “baby universes” created during inflation, a period of rapid expansion that is believed to be responsible for seeding the structures we observe today, such as galaxies and clusters of galaxies. During inflation, baby universes can branch off of our universe (image at the top of the page). A small baby (or “daughter”) universe would eventually collapse, but the large amount of energy released in the small volume causes a black hole to form.

Small baby universes are seen by us as primordial black holes, which conceal the underlying structure of multiple universes behind their “event horizons

“There is good reason to think that everything we can see in our sky represents only the smallest tip of the cosmic iceberg, writes Hooper, who was not involved in the Kavli study, in The Edge of Time . “During inflation, countless pieces of space were stretched into newly formed universes, populating a greater multiverse of disconnected worlds. And despite the fact that we have no way to observe this panoply of universes, there is every reason to suspect that it does, in fact, exist.”

A Diversity of Physical Laws

It is also possible, Hooper, adds, “different regions of the multiverse could be dictated by a diversity of physical laws. New forces and new forms of matter may rule many of these realms of existence. In some, there might be more—or fewer—than three dimensions of space. Many worlds may be utterly unlike anything we can imagine.”

The Event Horizon Boundary

An even more peculiar fate awaits a bigger baby universe, suggests the Kavli team. If it is bigger than some critical size, Einstein’s theory of gravity allows the baby universe to exist in a state that appears different to an observer on the inside versus the outside. An internal observer sees it as an expanding universe, while an outside observer (such as us) sees it as a black hole. In either case, the big and the small baby universes are seen by us as primordial black holes, which conceal the underlying structure of multiple universes behind their “event horizons.” The event horizon is a boundary below which everything, even light, is trapped and cannot escape the black hole.

In their paper, the team described a novel scenario for PBH formation and showed that the black holes from the “multiverse” scenario can be found using the HSC. Their work is an exciting extension of the HSC search of PBH that Masahiro Takada, a Principal Investigator at the Kavli IPMU, and his team are pursuing. The HSC team has recently reported leading constraints on the existence of PBHs in Niikura, Takada et. al. (Nature Astronomy 3, 524-534 (2019)

The Indispensable Hyper Suprime-Cam

The Hyper Suprime-Cam was indispensable, says the Kavli Institute, through its unique capability to image the entire Andromeda galaxy every few minutes. If a black hole passes through the line of sight to one of the stars, the black hole’s gravity bends the light rays and makes the star appear brighter than before for a short period of time. The duration of the star’s brightening tells the astronomers the mass of the black hole. With HSC observations, one can simultaneously observe one hundred million stars, casting a wide net for primordial black holes that may be crossing one of the lines of sight.

Source: Alexander Kusenko et al, Exploring Primordial Black Holes from the Multiverse with Optical Telescopes , Physical Review Letters (2020). DOI: 10.1103/PhysRevLett.125.181304

The Daily Galaxy, Maxwell Moe , astrophysicist, NASA Einstein Fellow , University of Arizona. via Dan Hooper, At the Edge of Time: Exploring the Mysteries of Our Universe’s First Seconds (Kindle Edition) and The Kavli Institute


These are the discoveries that made Stephen Hawking famous

Stephen Hawking is probably the most famous genius of the modern age.

But what exactly is he famous for &ndash apart from his astonishing resilience to an incapacitating disease, that instantly-recognizable retro-robotic voice, and his walk-on roles on The Simpsons and Star Trek?

Didn't he discover black holes? Or the Big Bang? Or tell us what time is, or something? No, no and no again. But it's hard to cut through the thickets of myth and get to the things that he really did discover. Hawking's own legend risks obscuring his real achievements.

Today, Hawking delivers this year's Reith Lecture: an appointment that signifies the speaker's status, not just as an expert in his or her discipline, but as a public intellectual. So now seems an opportune moment to put aside Hawking the icon and examine Hawking the physicist.

In several polls of the greatest physicists of the 20th century, or even of the top living physicists, Hawking is either absent or crawls in at the bottom of the list. Is he, then, not all he's cracked up to be?

Massive bodies, such as the Sun, cause space to curve around them

On the contrary, he is a huge presence in modern physics. It's just that physics has a lot of astonishing minds, and Hawking is one among many.

Hawking's genius, which arguably deserves a Nobel Prize, is to have brought together several different but equally fundamental fields of physical theory: gravitation, cosmology, quantum theory, thermodynamics and information theory.

It starts with general relativity: the theory of gravitation that Albert Einstein devised in the 1910s to replace that of Isaac Newton.

Newton's view of gravity assumed that massive objects created a "field" that permeated space, rather like the field of a magnet. This field enabled one body with mass, like the Earth, to exert a force on another, like the Moon or an apple. Newton did not claim to know what this force was. It was simply a fact of nature that all objects that possess mass create it.

Many physicists could not believe in something as bizarre as a singularity

But according to Einstein's theory of general relativity, gravity is not a field in space. Instead, it is a property of space itself.

The idea is that massive bodies, such as the Sun, cause space to curve around them. This distortion of space affects the motion of anything nearby. For instance, it holds the Earth in orbit around the Sun, like a marble rolling around the rim of a bowl.

One of the predictions of Einstein's theory is that a sufficiently large object, such as a really massive star, can collapse under the pull of its own gravity in a runaway process. All the mass shrinks into an infinitesimally small point of infinite density, called a singularity.

This collapse creates a region of space so severely warped by gravity that not even light can escape from it. We call this a black hole.

All this had been proposed in a 1939 paper by the American physicist Robert Oppenheimer &ndash who would later help develop the atomic bomb &ndash and his student Hartland Snyder.

It was only really at this point that Hawking's exceptional intellect began to shine through

But many physicists could not believe in something as bizarre as a singularity. So for years the idea languished, as others assumed that some process would intervene to prevent it.

It was only around 1959, when Hawking began his undergraduate studies at the University of Oxford, that physicists started to take the idea seriously. It was examined closely by John Wheeler at Princeton University in New Jersey, who allegedly gave black holes their name, Roger Penrose in the UK, and Yakov Zel'dovich in the Soviet Union.

After completing his degree in physics, Hawking started a PhD at the University of Cambridge, under the supervision of cosmologist Denis Sciama. His attention was captured by this resurgence of interest in general relativity and black holes.

It was only really at this point that Hawking's exceptional intellect began to shine through. He had just scraped a First at Oxford, and had a lot of mathematical catching-up to do. He had also recently been diagnosed with a form of motor neurone disease called amyotrophic lateral sclerosis, which would ultimately leave him almost entirely paralysed.

Hawking's disability was severe, and even walking with crutches was very difficult for him

Under Sciama's guidance, Hawking began thinking about the Big Bang theory: the idea that the universe began as a tiny speck that subsequently expanded. Nowadays this is widely accepted, but at the time it was still up for debate.

Hawking realised that the Big Bang was rather like the collapse of a black hole in reverse.

He developed this idea with Penrose. In 1970 the two of them published a paper showing that general relativity implies that the universe must have begun as a singularity.

By this time Hawking's disability was severe, and even walking with crutches was very difficult for him. In late 1970, as he was getting laboriously into bed one night, he had a sudden realisation about black holes: one that would spark a series of discoveries about how they behave.

Hawking realised that a black hole can only increase, never decrease, in size.

This may seem obvious. Since nothing that gets too close can escape, a black hole can only ever swallow more matter and thus gain mass.

The total entropy of the universe can only increase, never decrease

A black hole's mass in turn determines its size, measured as the radius of the event horizon, the point beyond which nothing can escape. This boundary will creep inexorably outwards like the skin of an inflating balloon.

But Hawking went further. He showed that a black hole can never be split into smaller ones &ndash even, say, through the collision of two black holes.

Then Hawking made another intuitive leap. He argued that the event horizon's ever-expanding surface area was analogous to another quantity that, according to physics, could only grow.

That quantity was entropy, which measures the amount of disorder in a system. Atoms stacked together regularly in a crystal have low entropy, while atoms drifting around randomly in a gas have high entropy.

According to the second law of thermodynamics, the total entropy of the universe can only increase, never decrease. In other words, the universe inevitably gets more disordered as it gets older. Hawking pointed out that these two rules of nature &ndash the increasing surface area of a black hole and the increasing entropy of the universe &ndash were oddly similar.

Most physicists &ndash including Hawking &ndash thought Bekenstein's proposal made no sense

When Hawking announced his result at the end of 1970, a young physicist named Jacob Bekenstein made a bold proposal: what if this wasn't just an analogy? Bekenstein suggested that the surface area of a black hole's event horizon might be a measure of the black hole's entropy.

But that seemed wrong. If an object has entropy, it must also have a temperature. And if it has a temperature, then it must radiate energy, yet the whole point of a black hole is that nothing gets out.

For this reason, most physicists &ndash including Hawking &ndash thought Bekenstein's proposal made no sense. Even Bekenstein himself said that the black hole's apparent temperature couldn't be "real" since it leads to a paradox.

But when Hawking set out to prove Bekenstein wrong, he found that the young student was, as he later admitted, "basically correct". In order to show this, he had to bring together two areas of physics that nobody else had managed to unify: general relativity and quantum theory.

Quantum theory is used to describe invisibly small things, like atoms and their component particles, while general relativity is used to describe matter on the cosmic scale of stars and galaxies.

According to quantum theory, allegedly empty space is in fact far from a void

The two theories seem fundamentally incompatible. General relativity assumes that space is smooth and continuous like a sheet, whereas quantum theory insists that the world and everything in it is grainy at the smallest scales, parcelled into discrete lumps.

Physicists have struggled for decades to unify the two theories &ndash which might then point to a "theory of everything". Such a theory is, to use an apt cliché, a holy grail of modern physics.

In his early career Hawking expressed a yearning for such a theory, but his analysis of black holes did not pretend to offer one. Instead, his quantum analysis of black holes used a sort of patchwork of the two existing theories.

According to quantum theory, allegedly empty space is in fact far from a void, because space cannot be smoothly, absolutely empty at all scales. Instead it is alive with activity.

Pairs of particles are constantly fizzing spontaneously into existence, one made of matter and the other antimatter. One of the particles has positive energy and the other negative, so overall no new energy is being created. The two then annihilate one another so quickly that they cannot be directly detected. As a result, they are called "virtual particles".

Hawking had proved himself wrong: black holes can get smaller after all

Hawking suggested that these pairs of particles could be upgraded from virtual to real, but only if they are created right next to a black hole.

There is a chance that one of the pair will be sucked inside the event horizon, leaving its partner stranded. This severed twin may then shoot out into space. If the negative-energy particle is absorbed by the black hole, the total energy of the black hole decreases, and therefore so does its mass. The other particle then carries away positive energy.

The end result is that the black hole radiates energy, now known as Hawking radiation, while gradually getting smaller. In other words, Hawking had proved himself wrong: black holes can get smaller after all. This is tantamount to saying that the black hole will slowly evaporate, and that it is not truly black at all.

What's more, that shrinkage would not necessarily be gradual and sedate.

In 1971 Hawking conceived a radical new vision of black holes. During the Big Bang, he suggested, some lumps of matter could have collapsed into miniature black holes. Each lump would weigh billions of tons, which sounds a lot but is far smaller than the Earth, and the resulting black hole would be smaller than an atom.

Because a black hole's temperature increases as its event horizon's surface area gets smaller, black holes this tiny would be hot: Hawking described them as "white hot". They would fizz with Hawking radiation, shedding mass until they eventually disappeared.

And they would not go quietly. A mini-black hole would get hotter as it got smaller, until eventually it would explode with the energy of a million one-megaton hydrogen bombs.

Hawking outlined his theory of Hawking radiation and exploding primordial mini-black holes in a paper in Nature in 1974. It was a shocking, controversial idea. Yet nowadays most physicists believe that Hawking radiation really will be generated by black holes.

So far nobody has managed to detect this radiation. That's not surprising, though: an ordinary black hole's temperature would barely be above absolute zero, so the energy it emits as Hawking radiation would be extremely tiny.

Seven years later, Hawking announced another disturbing implication of disappearing black holes. They destroy information, he said.

When particles or light rays pass inside a black hole's event horizon, they never return to the rest of the universe. Any such entity can be considered to carry information: for example, information about a particle's mass and position. This information is also locked away inside the black hole.

However, what happens to that information if the black hole evaporates? There are two possibilities: either it is somehow encoded in the Hawking radiation emitted by the black hole, or it is gone for good. Hawking claimed that it vanished.

When Hawking suggested that black holes destroy information, Susskind argued that he was plain wrong

When Hawking spoke in San Francisco in 1981 about the paradox of vanishing information in black-hole physics, the American physicist Leonard Susskind disagreed. He was one of the few who appreciated just how disturbing it would be if information were lost from the universe.

We like to imagine that causes come before their effects, not the other way around. In principle, although generally not in practice, that means we could trace and reconstruct the history of any particle in the universe based on the information about its current state.

But that reconstruction from effects to cause would become impossible if information is being destroyed in black holes. If information is truly being lost, the whole notion of cause and effect starts to look shaky.

So when Hawking suggested that black holes destroy information, Susskind argued that he was plain wrong.

The debate raged, in a fairly collegial manner, for decades. In 1997 it took on the form of a wager, something Hawking loves to indulge. Hawking bet John Preskill of the California Institute of Technology an encyclopaedia that information was indeed lost in black holes, while Preskill bet that it was not.

He tried to describe the Big Bang in quantum mechanical terms

At a conference in Dublin in 2004, Hawking finally conceded that Susskind was right &ndash and that Preskill should get his encyclopaedia. But in typically stubborn fashion, he qualified that statement by claiming that the information was only returned to the universe in a corrupted form that was virtually impossible to read, and that he had proved that this was so.

Hawking spelt out his argument in a short paper the following year. It did not convince everyone that his argument was better than Susskind's.

The episode was characteristic of Hawking's style. He is bold and brilliant, but not always rigorous enough to fully persuade, and sometimes seemingly driven by an intuition that can turn out to be quite wrong &ndash as when he bet against experimental detection of the Higgs particle.

The melange of general relativity, quantum theory, thermodynamics and information theory in Hawking's work on black holes is innovative and remarkable. Nothing else he has done has equalled it.

The very concept of an "origin" in time vanishes into the quantum foam

In the 1980s he tried to describe the Big Bang in quantum mechanical terms. Working with James Hartle, he developed a simple quantum equation that supposedly describes the entire universe in its early stages. But it does so in such general terms that, for many physicists, it doesn't say anything very meaningful.

The one thing the equation does suggest, however, is that it is futile to ask about the ultimate origin of the universe.

When the universe was still extremely tiny, less than a billionth of a yoctometre across, quantum theory implies that the distinction between space and time was extremely fuzzy. That means the early universe did not have meaningful boundaries in time or space, even though it was still self-contained. The very concept of an "origin" in time vanishes into the quantum foam.

This is the model explained in Hawking's best-selling A Brief History of Time (1988), which secured his status as a global celebrity. The idea is still debated.

There is now a sense that Hawking is tinkering, inventively but somewhat marginally, at the end of his career, taking thoughtful excursions into ideas largely conceived by others. He has more than earned the right to do that.

We as a society are still uncomfortable with disability

It is almost unfortunate that the iconic Hawking has so much eclipsed the physicist. Nowadays, nothing can be spoken in that trademark android monotone without immediately acquiring oracular status and being breathlessly reported.

This is the flipside of the otherwise life-affirming Hawking story. There is a presumption that he must be an endless source of gnomic wisdom. In fact he is fallible, just like every other human being regardless of their genius. His story is an inspiring one, but that doesn't mean we should deny him this aspect of his humanity.

Perhaps it is because we as a society are still uncomfortable with disability. We are strangely fascinated with the idea that a severely disabled person in a wheelchair can be enormously intelligent. We should not be surprised, and the fact that we are says more about us than it does about Stephen Hawking.


Time lapse footage captures the magnificent stars passing over the UK.

The Milky Way above Ijen Volcano, Malaysia

In their cosmology model, the cyclic nature of the universe occurs as a result of incorporating quantum effects into a cosmological model of the universe.

Prof Faizal explained that even though there are many different mind-bending approaches to quantum gravity, like string theory and loop quantum gravity, what most of these different approaches have in common is that there is a minimum length below which space does not exist.

Many of these approaches also predict that there is also a maximum energy and no object in the universe can have an energy beyond that maximum energy.

They research team incorporated the effect of having a minimum length and an maximum energy into a cosmological model, and then they ended up with a cyclic universe.

Asked about the philosophical and even possible theological implications of his work Prof. Mir said: ''No one draws any philosophical or theological implications of a finite or an infinite spatial dimension, and time is just another dimension, so why should it be treated any differently.

&ldquoIn any case, I do not believe in a God of gaps, with big bang being a big gap, but in a God who made the mathematics describing reality so perfect that there are no gaps, not now and not at big bang.''