Monday, October 1, 2012

On the Zen of the Big Bang and Nothingness

My good friend George commented on my Zen of Nothingness posting, to wit:
"Your mistakes are too numerous to discuss individually; we will need several hours to do that!
But your basic mistake is straightforward: You're looking at only one side of a two-sided state-of-being. Try thinking about what existed before the Big Bang. How did our "something" come into existence out of "nothing"? When you get a handle on that question you'll have a better understanding of what happens next."

So, I thought it might be useful to share with our readers a few of the lines of thinking about what existed before the Big Bang. There are many, but here are three I recently came across.
Just trying to be helpful here.





The Birth of Time: Quantum Loops Describe the Evolution of the Universe

ScienceDaily (Dec. 17, 2010) — What was the Big Bang and what happened before it? Scientists from the Faculty of Physics, University of Warsaw have attempted to answer the question. Within the framework of loop quantum gravity they have put forward a new theoretical model, which might prove useful for validating hypotheses about events prior to the Big Bang. This achievement is one of the few models describing the full Einstein's theory and not merely its greatly simplified version.



Physicists from the Faculty of Physics, University of Warsaw have put forward -- on the pages of Physical Review D -- a new theoretical model of quantum gravity describing the emergence of space-time from the structures of quantum theory. It is not only one of the few models describing the full general theory of relativity advanced by Einstein, but it is also completely mathematically consistent. "The solutions applied allow to trace the evolution of the Universe in a more physically acceptable manner than in the case of previous cosmological models," explains Prof. Jerzy Lewandowski from the Faculty of Physics, University of Warsaw (FUW).

While the general theory of relativity is applied to describe the Universe on a cosmological scale, quantum mechanics is applied to describe reality on an atomic scale. Both theories were developed in the early 20th century. Their validity has since been confirmed by highly sophisticated experiments and observations. The problem lies in the fact that the theories are mutually exclusive.

According to the general theory of relativity, reality is always uniquely determined (as in classical mechanics). However, time and space play an active role in the events and are themselves subject to Einstein's equations. According to quantum physics, on the other hand, one may only gain a rough understanding of nature. A prediction can only be made with a probability; its precision being limited by inherent properties. But the laws of the prevailing quantum theories do not apply to time and space. Such contradictions are irrelevant under standard conditions -- galaxies are not subject to quantum phenomena and quantum gravity plays a minor role in the world of atoms and particles. Nonetheless, gravity and quantum effects need to merge under conditions close to the Big Bang.

Traditional cosmological models describe the evolution of the Universe within the framework of the general theory of relativity itself. The equations at the core of the theory suggest that the Universe is a dynamic, constantly expanding creation. When theorists attempt to discover what the Universe was like in times gone by, they reach the stage where density and temperature in the model become infinite -- in other words, they lose their physical sense. Thus, the infinities may only be indicative of the weaknesses of the former theory and the moment of the Big Bang does not have to signify the birth of the Universe.

In order to gain at least some knowledge of quantum gravity, scientists construct simplified quantum models, known as quantum cosmological models, in which space-time and matter are expressed in a single value or a few values alone. For example, the model developed by Ashtekar, Bojowald, Lewandowski, Pawłowski and Singh predicts that quantum gravity prevents the increase of matter energy density from exceeding a certain critical value (of the order of the Planck density). Consequently, there must have been a contracting universe prior to the Big Bang. When matter density had reached the critical value, there followed a rapid expansion -- the Big Bang, known as the Big Bounce. However, the model is a highly simplified toy model.

The real answer to the mystery of the Big Bang lies in a unified quantum theory of matter and gravity. One attempt at developing such a theory is loop quantum gravity (LQG). The theory holds that space is weaved from one-dimensional threads. "It is just like in the case of a fabric -- although it is seemingly smooth from a distance, it becomes evident at close quarters that it consists of a network of fibres," describes Wojciech Kamiński, MSc from FUW. Such space would constitute a fine fabric -- an area of a square centimetre would consists of 1066 threads.

Physicists Marcin Domagała, Wojciech Kamiński and Jerzy Lewandowski, together with Kristina Giesel from the Louisiana State University (guest), developed their model within the framework of loop quantum gravity. The starting points for the model are two fields, one of which is a gravitational field. "Thanks to the general theory of relativity we know that gravity is the very geometry of space-time. We may, therefore, say that our point of departure is three-dimensional space," explains Marcin Domagała, PhD (FUW).

The second starting point is a scalar field -- a mathematical object in which a particular value is attributed to every point in space. In the proposed model, scalar fields are interpreted as the simplest form of matter. Scalar fields have been known in physics for years, they are applied, among others, to describe temperature and pressure distribution in space. "We have opted for a scalar field as it is the typical feature of contemporary cosmological models and our aim is to develop a model that would constitute another step forward in quantum gravity research," observes Prof. Lewandowski.

In the model developed by physicists from Warsaw, time emerges as the relation between the gravitational field (space) and the scalar field -- a moment in time is given by the value of the scalar field. "We pose the question about the shape of space at a given value of the scalar field and Einstein's quantum equations provide the answer," explains Prof. Lewandowski. Thus, the phenomenon of the passage of time emerges as the property of the state of the gravitational and scalar fields and the appearance of such a state corresponds to the birth of the well-known space-time. "It is worthy of note that time is nonexistent at the beginning of the model. Nothing happens. Action and dynamics appear as the interrelation between the fields when we begin to pose questions about how one object relates to another," explains Prof. Lewandowski.

Physicist from FUW have made it possible to provide a more accurate description of the evolution of the Universe. Whereas models based on the general theory of relativity are simplified and assume the gravitational field at every point of the Universe to be identical or subject to minor changes, the gravitational field in the proposed model may differ at different points in space.

The proposed theoretical construction is the first such highly advanced model characterized by internal mathematical consistency. It comes as the natural continuation of research into quantization of gravity, where each new theory is derived from classical theories. To that end, physicists apply certain algorithms, known as quantizations. "Unfortunately for physicists, the algorithms are far from precise. For example, it may follow from an algorithm that a Hilbert space needs to be constructed, but no details are provided," explains Marcin Domagała, MSc. "We have succeeded in performing a full quantization and obtained one of the possible models."

There is still a long way to go, according to Prof. Lewandowski: "We have developed a certain theoretical machinery. We may begin to ply it with questions and it will provide the answers." Theorists from FUW intend, among others, to inquire whether the Big Bounce actually occurs in their model. "In the future, we will try to include in the model further fields of the Standard Model of elementary particles. We are curious ourselves to find out what will happen," says Prof. Lewandowski. 

 


 


 

And for those of you not already hopelessly lost in the mists of time and QuantumTalk, here is yet another discussion of this same basic question. 

What happened before the Big Bang?


We spend a lot of time thinking about futurism, but the past is pretty interesting, too. In this week's "Ask a Physicist" we get extra speculative and think about what things may have been like before the beginning of time. What was there before the Big Bang? Did anything exist before our current universe? Here's what we know.

For the most part, I try to keep these columns as by-the-numbers as possible. I generally want to focus on the consensus view of physics, and only like to veer off into the realm of crackpot science and speculation every so often.

But sometimes people have burning questions that they need answered that physics doesn't have an authoritative answer to. Discussion section, here's your lucky day! Step into your time cube and consider a question put to me by Dave Ranautta and several others. They ask:

What was there before the big bang? I appreciate that there are no facts concerning what existed prior (if anything) but are there popular theories?

Standard Answer: Nothing. So please don't ask.

I've talked a lot about the expanding universe in this column. The standard picture comes from general relativity, which describes a sort of stretching of space-time. The normal analogy is to think of us as ants on a balloon. In the past, the universe (aka "the balloon") was smaller than it is now, and, taken far enough back, the universe, presumably, was a single point. That was the moment of the big bang.

In the normal general relativity picture of things, the moment of creation produced not only space, but time; the two are incredibly intermixed, after all. To Einstein, talking about what happened before the Big Bang is just as nonsensical as asking what happens if you travel north of the North Pole. There just isn't just a place, or consequently such a time.

This is likely to make people squeamish. After all, if there was no time before the Big Bang (or no space, for that matter) where did we come from? Shouldn't there be something resembling causality in the universe?

What are our options?

We have some wiggle room, however. As I've discussed previously (and far less speculatively) not only don't we know what happened before the Big Bang, we don't even know what happened in the instant immediately following the Big Bang.

Our knowledge of physics in the first 10^-44 seconds after the beginning (which, admittedly, is a pretty damn short time) is virtually non-existent. This instant is known as the Planck Time, and since we don't know what happened before the Planck time with anything even remotely resembling certainty, we absolutely don't know what happened before the Big Bang. Regardless, logic dictates that we're left with one of two possibilities:

§  The universe had some sort of beginning, in which case we're left with the very unsettling problem of what caused the universe in the first place.

§  The universe has been around forever, in which case there's literally an infinite amount of history, both before and after us.


Neither of these is satisfying. Take the Old Testament view, for instance. We're to understand that God created the world. In that case our universe has a definite beginning. However, God himself is supposed to be eternal. What was he doing before he created our universe? It's no more satisfying to assert that the universe has been here all along. Is there literally an infinite amount of history? That doesn't make sense.

As a particularly clever cheat (or theory, if you prefer), in 1982 Alex Vilenkin of Tufts University showed how what we've learned from quantum mechanics might shed light on the how the universe popped into being.

Model #1: The Universe out of Nothing

Vilenkin noted that if we were to somehow start with a small bubble of a universe, two things could happen. If it were large enough, it would undergo exponential growth — just like our universe did in the first instants. If it were small, it would collapse.

Here's where things get weird. Quantum mechanics predicts all sorts of strange things, including half-dead/half-alive cats, or the possibility of teleportation. It also predicts the possibility that apparently impossible things are really just improbable. Image by CottonIJoe/Flickr.

For instance, it's possible (but brain-bendingly unlikely) that you could spontaneously find yourself teleported to Alpha Centauri (readers: please insert obligatory Hitchiker's reference here). More commonly radioactive decay can be thought of as a small piece of an atomic nucleus that shouldn't really be able to escape from the rest somehow randomly tunneling away. The universe is just like that sometimes.

In the same way, a small universe can randomly tunnel into a larger one. The amazing thing about Vilenkin's model is that even if you make the "little" universe as small as you like, this tunneling still can occur. It even works if the little universe has no size at all. You know what we call something with no size?

Nothing.

Prior to the Big Bang, the state of the universe was something that possessed (no fooling) zero size and for which time was essentially undefined. The universe then tunneled out of nothing into the expanding universe we know and love.

The problem is that the "nothing" that the universe popped out of wasn't really nothing. It had to know about quantum mechanics somehow, and we've always been taught to think that the physics is a property of the universe. It's troubling to think that the physics existed before the universe did, or, for that matter, before time did.

Of course, this is the basic problem with any definite origin for the universe. Somehow all of the complexity had to be created from nothing, and it's difficult to reconcile that.

The other possibility seems equally troubling. The universe might literally be eternal — or at least have an infinite history. While it's not clear what the theological implications of an infinite universe, we can at least try to figure out how an infinite universe might work.

Model #2: The Universe gave birth to itself

In 1998, J. Richard Gott and Li Xin Li, both then at Princeton, proposed a model in which the universe arose from what can only be described as a time machine. Gott and Li showed that it was possible to solve Einstein's equations of general relativity in such a way that a universe started off going around and around in a continuous loop, and that that loop could serve as the "trunk" of a tree that sprouted, giving rise to our own universe. Since a picture says a thousand words, let's illustrate with their own figure.Credit J.R. Gott and L.-X. Li
The way to read this image is that for the most part, time travels from bottom to top, and that everything begins with the little loop at the bottom. That is the origin of the universe. This means that the universe has no beginning, since the loop goes around and around infinitely.

We can talk about the "time after the Big Bang" as the time after the loop sprouted off into the future and a universe was born. You'll also notice that there isn't just a single horn coming out of the initial time loop, but many. This is totally consistent with the concept of a multiverse, just to add another level of speculative awesomeness to the discussion.

Model #3: This Is Not the First Universe

For a long time, cosmologists played around with the idea that the universe might ultimately collapse on itself. Then, in 1998, two teams discovered that the universe was accelerating, essentially demonstrating that we were way off base. You may also recall that these folks won the Nobel prize this year for their discovery.

Even though on the surface it doesn't look as though our universe will ultimately collapse under its own weight, there is still a great deal of allure to this picture. If the universe were somehow to end in a big crunch, then maybe what's really happening is that we'll eternally undergo a series of expansions and contractions, on and on for infinity. Our universe, in this case, is just one in an infinite series.

The problem with this (besides the fact that there is too little stuff in our universe to make it collapse again) is one of disorder. As we've discussed previously, the universe loves disorder. If you've ever stacked soda cans, there's only one way to stack them, and that's straight up. But if you knock them over, they go everywhere. There are more ways to destroy a soda can tower then there are to build one, and as time goes on, the universe finds ways of destroying all other forms of order, too.

If our universe was the result of a series of expansions and collapses, then our Big Bang occurred billions or trillions of years after some beginning (and what caused that?), so it would have had a very long time to get disordered. But it isn't. Looking back, our universe was very smooth, and in a very high state of order. This wouldn't solve the problem at all.

But in recent years, there have been a number of new cyclic models that allow an eternal universe to exist. In 2002, Paul Steinhardt, of Princeton University, and Neil Turok, of Cambridge, devised a model that exploits the extra dimensions found in string theory. String theory supposes that our universe might not be three-dimensional at all, but might have as many as ten spatial dimensions. Our own universe might simply live on a three-dimensional membrane (or "brane" for short) that is floating through the universe, barely interacting with the other universes.

However, the different branes (universes) could interact gravitationally. In this model, the dark energy that accelerates the universe isn't a real thing at all, but just a remnant of the gravitational attraction between branes, and the dark matter is just ordinary matter on the other, nearby brane. Occasionally the branes collide with one another, which would set off "Big Bangs" within the different branes and then everything would proceed as we've already seen.

These models are extremely elegant and deal with the whole "increase of disorder" problem in a really novel way. In cycle after cycle, the branes get more and more stretchy, which means that the disorder gets spread out over a larger and larger volume. The local patch that we call our universe, however, is just a small patch of the brane, so we seem to start nearly from scratch at each go-round. It sounds great, but a big problem is that these models require string theory to be correct, and on that the jury is definitely still out.

And there are even more models, some including extra dimensions, some include concepts like "loop quantum gravity," some infinite in time, and some with a definite duration. At the end of the day, the Big Bang theory has the same basic problem as evolutionary theory. Both do a nearly perfect job in explaining how the universe (or life) changed when it first came about, but neither can explain how things really got started in the first place.

This column was adapted from parts of Chapter 7 of A User's Guide to the Universe.

Dave Goldberg is the author, with Jeff Blomquist, of "A User's Guide to the Universe." (follow us on twitter, facebook, twitter or our blog.) He is an Associate Professor of Physics at Drexel University and is currently working on "The Universe in the Rearview Mirror," a new book all about symmetry that will be published by Dutton in 2013. Please send email to askaphysicist@io9.com with any questions about the universe.

 

Now, for those of you who like to obtain "all the news that's fit to print" from our very own NY Times, here is their interpretation of the question.

What Happened Before the Big Bang?


By DENNIS OVERBYE
Published: November 11, 2003

Like baseball, in which three strikes make an out, three outs on a side make an inning, nine innings make a regular game, the universe makes its own time. There is no outside timekeeper. Space and time are part of the universe, not the other way around, thinkers since Augustine have said, and that is one of the central and haunting lessons of Einstein's general theory of relativity.

In explaining gravity as the ''bending'' of space-time geometry, Einstein's theory predicted the expansion of the universe, the primal fact of 20th-century astronomy. By imagining the expansion going backward, like a film in reverse, cosmologists have traced the history of the universe credibly back to a millionth of a second after the Big Bang that began it all.

But to ask what happened before the Big Bang is a little bit like asking who was on base before the first pitch was thrown out in a game, say between the Yankees and the Red Sox. There was no ''then'' then.

Still, this has not stopped some theorists with infinity in their eyes from trying to imagine how the universe made its ''quantum leap from eternity into time,'' as the physicist Dr. Sidney Coleman of Harvard once put it.

Some physicists speculate that on the other side of the looking glass of Time Zero is another universe going backward in time. Others suggest that creation as we know it is punctuated by an eternal dance of clashing island universes.

In their so-called quantum cosmology, Dr. Stephen Hawking, the Cambridge University physicist and author, and his collaborators envision the universe as a kind of self-contained entity, a crystalline melt of all possibilities existing in ''imaginary time.''

All these will remain just fancy ideas until physicists have married Einstein's gravity to the paradoxical quantum laws that describe behavior of subatomic particles. Such a theory of quantum gravity, scientists agree, is needed to describe the universe when it was so small and dense that even space and time become fuzzy and discontinuous. ''Our clocks and our rulers break,'' as Dr. Andrei Linde, a Stanford cosmologist likes to put it.

At the moment there are two pretenders to the throne of that ultimate theory. One is string theory, the putative ''theory of everything,'' which posits that the ultimate constituents of nature are tiny vibrating strings rather than points. String theorists have scored some striking successes in the study of black holes, in which matter has been compressed to catastrophic densities similar to the Big Bang, but they have made little progress with the Big Bang itself.

String's lesser-known rival, called loop quantum gravity, is the result of applying quantum strictures directly to Einstein's equations. This theory makes no pretensions to explaining anything but gravity and space-time. But recently Dr. Martin Bojowald of the Max Planck Institute for Gravitational Physics in Golm, Germany, found that using the theory he could follow the evolution of the universe back past the alleged beginning point. Instead of having a ''zero moment'' of infinite density -- a so-called singularity -- the universe instead behaved as if it were contracting from an earlier phase, according to the theory, he said. As if the Big Bang were a big bounce.
 
Oh, there's one minor problem I have noted in all of the material I have read on Quantum Physics. None of it seems to shed any light on what happens to us after our filament burns out and we go dark. Maybe we need to consult one of our Quantum Physicists about that minor omission in their papers. Dr. Hawking . . .??? Dr. Einstein . . .Hello??? Anyone there???
Post a Comment