Before the Big Bang: A Twin Universe?

Before the Big Bang: A Twin Universe?
The new study suggests that the universe that came before our own universe was its identical twin. Image credit: NASA and ESA.

Until very recently, asking what happened at or before the Big Bang was considered by physicists to be a religious question. General relativity theory just doesn’t go there – at T=0, it spews out zeros, infinities, and errors – and so the question didn’t make sense from a scientific view.

But in the past few years, a new theory called Loop Quantum Gravity (LQG) has emerged. The theory suggests the possibility of a “quantum bounce,” where our universe stems from the collapse of a previous universe. Yet what that previous universe looked like was still beyond answering.

Now, physicists Alejandro Corichi from Universidad Nacional Autónoma de México and Parampreet Singh from the Perimeter Institute for Theoretical Physics in Ontario have developed a simplified LQG model that gives an intriguing answer: a pre-Big Bang universe might have looked a lot like ours. Their study will appear in an upcoming issue of Physical Review Letters.

“The significance of this concept is that it answers what happened to the universe before the Big Bang,” Singh told “It has remained a mystery, for models that could resolve the Big Bang singularity, whether it is a quantum foam or a classical space-time on the other side. For instance, if it were a quantum foam, we could not speak about a space-time, a notion of time, etc. Our study shows that the universe on the other side is very classical as ours.”

The finding builds on previous research, with some important differences. Last year, Penn State physicist Martin Bojowald used a simplified version of LQG to show that a universe “on the other side” of the bounce could have existed. However, although that model produced valid math, no observations of our current universe could have lead to any understanding of the state of the pre-bounce universe, as nothing was preserved across the bounce. Bojowald described this as a sort of “cosmic amnesia.”

But Corichi and Singh have modified the simplified LQG theory further by approximating a key equation called the quantum constraint. Using their version, called sLQG, the researchers show that the relative fluctuations of volume and momentum in the pre-bounce universe are conserved across the bounce.

“This means that the twin universe will have the same laws of physics and, in particular, the same notion of time as in ours,” Singh said. “The laws of physics will not change because the evolution is always unitary, which is the nicest way a quantum system can evolve. In our analogy, it will look identical to its twin when seen from afar; one could not distinguish them.”

That means that our universe today, roughly 13.7 billion years after the bounce, would share many of the same properties of the pre-bounce universe at 13.7 billion years before the bounce. In a sense, our universe has a mirror image of itself, with the Big Bang (or bounce) as the line of symmetry.

“In the universe before the bounce, all the general features will be the same,” said Singh. “It will follow the same dynamical equations, the Einstein’s equations when the universe is large. Our model predicts that this happens when the universe becomes of the order 100 times larger than the Planck size. Further, the matter content will be the same, and it will have the same evolution. Since the pre-bounce universe is contracting, it will look as if we were looking at ours backward in time.”

Specifically, Corichi and Singh calculate that the change in relative fluctuations across the bounce is less than 10-56, a number which becomes even smaller for universes that grow larger than 1 megaparsec (our universe is somewhere between 3,000 and 6,000 megaparsecs).

As the researchers explain, having an identical twin universe would not necessarily mean that every single feature of both universes would be identical. For instance, it doesn’t imply that there was another you that existed at some point, a person who has already lived your life.

“If one were able to look at certain microscopic properties with a very strong microscope – a very high-energy experiment probing the Planck scale – one might see differences in some quantities, just as one might see that twins have different fingerprints or one has a mole and the other does not, or a different DNA,” Singh said.

As Singh explained, there are still many questions regarding the details of the possible pre-bounce universe.

“The biggest question is whether these features survive when we consider more complex situations,” he said. “For example, one would like to know whether some structures present in the previous universe – like galaxies – will leave some imprint in the new expanding one that will give rise to identical structure or just 'similar.' For instance, it could happen that, in the previous universe, galaxies formed in a different way, so one might have a different distribution of galaxies on the other side. We will be able to answer this question when we understand these models.”

Ultimately, Corichi and Singh’s model might even tell us what a future universe would look like. Depending on how fast our present universe is accelerating – which will ultimately determine its fate – there’s a possibility that a generalization of the model would predict a re-collapse of our own universe.

“Such a universe will have many bounces from one branch to another,” Singh said. “It is also possible that universes in different branches will be identical.”

More information: Corichi, Alejandro, and Singh, Parampreet. “Quantum bounce and cosmic recall.” Arxiv:0710.4543v2. Accepted for publication in Physical Review Letters.

Copyright 2008
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of

Explore further

Our Universe: A Quantum Loop

Citation: Before the Big Bang: A Twin Universe? (2008, April 9) retrieved 26 June 2019 from
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Feedback to editors

User comments

Apr 09, 2008
Um. Two words: measurable predictions.

Apr 09, 2008
How is this theory different from the Big Bang --> Great Collapse --> Big Bang theory?

Apr 09, 2008
The Universe is infinite and the only non-possibility is no possibility at all.

"Rabble, rabble, rabble - Non-sense!" shout the geniuses and intellectuals, "It simple isn't possible for the Universe to be infinite because of such and such a law and formula and perspective! We can SEE the edge of the Universe! How foolish you are earls to simply ASSUME!"

And who can argue with them? Them, having traveled from edge to edge of the vast cosmos, back and forth through the beginnings and ends of time...

If you can imagine something, it can be made real. And the only thing I can't imagine is nothing at all.

But congratulations to the team for making their assumptions fit an equation.

Apr 09, 2008
>"The significance of this concept is that it answers what happened to the universe before the Big Bang,"

It doesnt answer anything, its just some wild speculation based on approximate equations of a simplified version of one of many proposed theories of quantum gravity which was unable so far to provide any testable hypothesis.

It is not science.

Apr 09, 2008
Maybe the first one was the real earth and we are the heaven?

Apr 09, 2008
The answer is simple. The expansion theory is valid. All things accelerate to the point of
near non-existence. At that point a gravity loop is left and from the gravity loop the big bang. I would be willing to bet that there would be some radiation left. Probably similar to the background radiation left by the big bang itself.

Apr 09, 2008
This comment has been removed by a moderator.

Apr 09, 2008
It is difficult to understand the concept of time, but the twin universe is our universe with time perceived moving backwards. Time is a looped dimension. For our perception, we move forward in time, but it is only a perception. We are unable to distinguish if we would be moving backwards in time. Time itself doesn't move anywhere. Our universe exists in every point of time, we just can't see it, since we all stuck in the same time frame. At some point we will reach the opposite point from the big bang and time will stop for us. We will not even notice. The universe will play the history backwards and shrink back into singularity at the time of the big bang.. and everything will repeat itself.

Apr 09, 2008
Consider the idea that this universe is a virtual reality.
Wikipedia, overview
Nick Bostrom, 2002
Brian Whitworth, 2007

In addition to those arguments, one way to explain the apparent fact that space and time and mass and energy are quantized would be to say that their quantization is a result of the fact that the 3-D monitor, in which our virtual reality is displayed, has a finite spatial screen resolution, and a finite repetition rate.

So if this universe is a virtual reality, we need to ask the originator of this virtual reality, yes?

Apr 09, 2008
It is still an open question whether their astrophysicists observe(d) their universe expanding (i.e. time reversed relative to our experince) or a contracting universe (time direction conserved)as this is an entirely subjective experience anyhow....

Apr 10, 2008
The laws of physics say that energy must be conserved and momentum must be conserved.
From the point of the big bang on, matter has conserved its momentum by expanding outward.
But before the big bang, there must still have been energy because energy is conserved. I don't know why all the energy of the universe would stay still (in one spot) for half of an eternity and then explode outward. It seems to me that there must have been a previous collapse of energy that brought it all to one point.

Apr 10, 2008
Just pick a random universe with random boundary conditions.

Apr 10, 2008
Wow congratulations to this "scientist". He figured out what I stumbled upon in the sixth grade. Not all the math but the general idea.

Things are born, get old, then die, and are reborn, ware have I heard that before?

All this about the last universe being just like this one is crap too. Tweak any set of variables such as mass or collapse velocity and it would look completely different without changing the result.

What happened before the big bang can never really be proven, this makes it a matter of faith not science. Science is based on provable fact not useless speculation.

Apr 10, 2008
What a crock.

The Universe is INFINITE. There is NO EDGE - it just keeps going. It has no beginning, it has always been. It has no end, it will always be.
The ARROGANCE of all of the scientists assumes that WE ARE IN THE CENTER OF THE UNIVERSE. We are not. There is no center, it is infinite. If we had a big bang on our salt speck it would have no effect on the salt speck off the coast of Japan.

In many ways, we are still applying scientific thought as if we were in the days of Galileo and Copernicus - when will science figure out we are not at the center of the universe?

What make you believe in we are assumed the "center" of universe in science? We are already in 21st century, man. The arrogance is in you, not the scientists.

And mind you, while our universe were found no edge, that doesn't mean the universe is infinitely large. The space can warp just like the earth is round. The ground we stand on has no end but nontheless a limited area. Same as our universe.

Apr 10, 2008
This comment has been removed by a moderator.

Apr 11, 2008
Wouldn't this create another Information Paradox?

I know that's meant to be applied to Black Holes, but the same basic idea seems to apply.

Apr 12, 2008
I found this rather amusing as it reminded me of something I read in Hitchhikers Guide to the Galaxy:

"There is a theory that states that is ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable."

Apr 14, 2008
> The Universe is INFINITE.

No, the universe is finite, but unbounded.

Apr 14, 2008
Yes, thanks, we all know what the textbook says.

Apr 15, 2008
If this study and our subsequent comments don't reek of religion, nothing does. Most (not all) are passionate statements of belief with absolutely no proof.

Apr 15, 2008
er... correction required? The authors seem to have lost a very large slice of our universe.

3000-6000 Megaparsecs? Try nearly 48,000

Apr 22, 2008
So .. start working on a way to preserve information past the crunch. And as this probably isn't the 1st time, chances are when you find some method that will work, you will find a message already waiting.

May 02, 2008
I got this site in the first place to learn about such. Turtles all the way down is what we have in that the law of conservation forces us to conclude that there is eternal Existence, however the number of universes. It is a matter of vacuum fluctuation energy.

May 13, 2008
I have had a "stringless string theory" that nobody has given me any feedback on. I hope that this theory will bridge the gap between Relativity and Quantum. I try to make everything compatible with the former, but, since I never really understood the latter, I can just hope.

Simply put, there are the three large spatial dimensions that we are familiar with, a number of small dimensions (probably six), plus time, which acts like an imaginary (in the sense of the square root of -1) dimension. Thus we may have 9 i dimensions.

The spatial dimensions vibrate or pulsate, getting repeatedly bigger and smaller. For the big dimensions, the period is billions or trillions of years; for the small dimensions, maybe yoctoseconds, or even shorter. What should I call this? Pulsating Yocto-Dimensions Theory (PYDT).

There is also a rule that every closed region of space, the hypervolume is constant. If one dimension gets larger, another must get smaller to compensate. The combined effect of the (assumed sinusoidal) pulsations of the small dimensions is to dilate the large dimensions, leading directly to Einsteinian Gravity, and eliminating the need for Gravitons or Higgs Bosons.

The overall intensity of the small-dimension pulsations (energy) leads to gravity, and, by applying Einstein's Equivalence Principle, mass. These vibrations or pulsations always travel at the speed of light. If all the motion is in the small dimensions, then you have a stationery particle. If all the motion is in the large dimensions, then you have a "massless" particle like a photon. A moving massive particle moves in both the large and small dimensions (or more properly, moves in the large dimensions and pulsates in the small dimensions), providing a novel explanation of time dilation that is not inconsistent with Minkowski's.

Now, there must be some sort of resonance between pulsations in different small dimensions in order to explain quantum effects. Perhaps the differences in phase between pulsations in different dimensions explains the various different non-gravitational forces of nature. I believe that Gravity is different, and is inherently non-quantum. If there are many Universes in the Multiverse, they all would have gravity, but their Quantized forces could be different.

Also, the Big Bang might have been when three of the previous small dimensions became our large dimensions, while the previous large dimensions became small dimensions.

This is just a nutshell outline.

May 13, 2008
Correction: Not "9 i" dimensions, but "9 i" dimensions.

May 13, 2008
OK, this seems to ignore plus signs. Where it says "9 i" dimensions, I mean "Nine plus eye", that is, the sum of three squared plus the square root of negative one.

May 15, 2008
I just want to raise another possibility -- as the large dimensions expand, the small (yocto) dimensions might be getting smaller, slowly changing the laws of physics. The observations of conditions from many billion of years ago might be skewed because the constants of physics may have been different back then, so inflation might be an illusion.

Jun 02, 2008
We will be hearing more- much more about this "twin" universe. The term "twin universe" is conceptually only the beginning of the concept. I have a description of a bifid universe cosmology posted at:

Best Wishes, Sam Cox

May 08, 2009
I can speculate on much cooler things with no supporting evidence.

May 09, 2009
Before the Twin Universe: A Big Bang?

Before the Big Bang: A Twi......zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

Jul 05, 2009
I like to think that the universe eventually collapses in on itself which creates a big bang that starts the cycle of existence over again.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more