What was here before the big bang

In other words, the complicated and, admittedly, poorly understood physics of this critical epoch may indeed allow for a radically revised view of our time and place in the cosmos. But to fully test this model, we'll have to wait for a new generation of cosmology experiments, so let's wait to break out the ekpyrotic champagne.

Paul M. Originally published on Live Science. Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community space. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in , and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe, to the earliest moments of the Big Bang, to the hunt for the first stars.

As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!

View Deal. Paul Sutter. See all comments Admin said:. PaulWolf said:. The space. If the weighted sum of all possible expansion histories yields some other kind of universe as the likeliest outcome, the no-boundary proposal fails. The problem is that the path integral over all possible expansion histories is far too complicated to calculate exactly. Countless different shapes and sizes of universes are possible, and each can be a messy affair. Even the minisuperspace calculation is hard to solve exactly, but physicists know there are two possible expansion histories that potentially dominate the calculation.

These rival universe shapes anchor the two sides of the current debate. Weirder expansion histories, like football-shaped universes or caterpillar-like ones, mostly cancel out in the quantum calculation. One of the two classical solutions resembles our universe. As in the real universe, density differences between regions form a bell curve around zero. If this possible solution does indeed dominate the wave function for minisuperspace, it becomes plausible to imagine that a far more detailed and exact version of the no-boundary wave function might serve as a viable cosmological model of the real universe.

The other potentially dominant universe shape is nothing like reality. As it widens, the energy infusing it varies more and more extremely, creating enormous density differences from one place to the next that gravity steadily worsens.

Density variations form an inverted bell curve, where differences between regions approach not zero, but infinity. If this is the dominant term in the no-boundary wave function for minisuperspace, then the Hartle-Hawking proposal would seem to be wrong. The two dominant expansion histories present a choice in how the path integral should be done. If the dominant histories are two locations on a map, megacities in the realm of all possible quantum mechanical universes, the question is which path we should take through the terrain.

Researchers have forked down different paths. In their paper, Turok, Feldbrugge and Lehners took a path through the garden of possible expansion histories that led to the second dominant solution.

Lacking a causal element, lapse is not quite our usual notion of time. Yet Turok and colleagues argue partly on the grounds of causality that only real values of lapse make physical sense. The Big Bang, then, would have represented the moment that classical physics took over as the major driver of the universe's evolution.

For Stephen Hawking, this moment was all that mattered: Before the Big Bang, he said, events are unmeasurable, and thus undefined. Or perhaps there was something else before the Big Bang that's worth pondering.

One idea is that the Big Bang isn't the beginning of time, but rather that it was a moment of symmetry. In this idea, prior to the Big Bang, there was another universe, identical to this one but with entropy increasing toward the past instead of toward the future. Increasing entropy, or increasing disorder in a system, is essentially the arrow of time, Carroll said, so in this mirror universe , time would run opposite to time in the modern universe and our universe would be in the past.

Proponents of this theory also suggest that other properties of the universe would be flip-flopped in this mirror universe. For example, physicist David Sloan wrote in the University of Oxford Science Blog , asymmetries in molecules and ions called chiralities would be in opposite orientations to what they are in our universe.

A related theory holds that the Big Bang wasn't the beginning of everything, but rather a moment in time when the universe switched from a period of contraction to a period of expansion.

This "Big Bounce" notion suggests that there could be infinite Big Bangs as the universe expands, contracts and expands again. Moreover, Augustine argued that the world was not made by God at a certain time, but that time and the universe had been created simultaneously [source: Villanova University ].

In the early 20th century, Albert Einstein came to very similar conclusions with his theory of general relativity. Just consider the effect of mass on time. A planet's hefty mass warps time -- making time run a tiny bit slower for a human on Earth's surface than a satellite in orbit. The difference is too small to notice, but time even runs more slowly for someone standing next to a large boulder than it does for a person standing alone in a field.

Based upon Einstein's work, Belgian cosmologist Rev. According to Einstein's theory of relativity, time only came into being as that primordial singularity expanded toward its current size and shape. Case closed? Far from it. This is one cosmological quandary that won't stay dead.

In the decades following Einstein's death, the advent of quantum physics and a host of new theories resurrected questions about the pre-big bang universe. Keep reading to learn about some of them. Here's a thought: What if our universe is but the offspring of another, older universe?

Some astrophysicists speculate that this story is written in the relic radiation left over from the Big Bang : the cosmic microwave background CMB.

Astronomers first observed the CMB in , and it quickly created problems for the Big Bang theory -- problems that were subsequently addressed for a while in with the inflation theory. This theory entails an extremely rapid expansion of the universe in the first few moments of its existence.

It also accounts for temperature and density fluctuations in the CMB, but dictates that those fluctuations should be uniform.

That's not the case.