This is obviously absurd, and what it really tells us is that we need new physics to solve this problem — our current toolkit just isn't good enough. Related: 8 ways you can see Einstein's theory of relativity in real life. To save the day we need some new physics, something that is capable of handling gravity and the other forces, combined, at ultrahigh energies. And that's exactly what string theory claims to be: a model of physics that is capable of handling gravity and the other forces, combined, at ultrahigh energies.
Which means that string theory claims it can explain the earliest moments of the universe. One of the earliest string theory notions is the "ekpyrotic" universe, which comes from the Greek word for "conflagration," or fire. In this scenario, what we know as the Big Bang was sparked by something else happening before it — the Big Bang was not a beginning, but one part of a larger process.
Extending the ekpyrotic concept has led to a theory, again motivated by string theory, called cyclic cosmology. I suppose that, technically, the idea of the universe continually repeating itself is thousands of years old and predates physics, but string theory gave the idea firm mathematical grounding.
The cyclic universe goes about exactly as you might imagine, continually bouncing between big bangs and big crunches, potentially for eternity back in time and for eternity into the future.
As cool as this sounds, early versions of the cyclic model had difficulty matching observations — which is a major deal when you're trying to do science and not just telling stories around the campfire. The main hurdle was agreeing with our observations of the cosmic microwave background, the fossil light leftover from when the universe was only , years old.
While we can't see directly past that wall of light, if you start theoretically tinkering with the physics of the infant cosmos, you affect that afterglow light pattern. But the ekpyrotic torch has been kept lit over the years, and a paper published in January to the arXiv database has explored the wrinkles in the mathematics and uncovered some previously missed opportunities.
The physicists, Robert Brandenberger and Ziwei Wang of McGill University in Canada, found that in the moment of the "bounce," when our universe shrinks to an incredibly small point and returns to a Big Bang state, it's possible to line everything up to get the proper observationally tested result. 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! Stephen Hawking chose the august setting to present what he would later regard as his most important idea: a proposal about how the universe could have arisen from nothing.
But where did the initial energy come from? The Big Bang theory had other problems. Physicists understood that an expanding bundle of energy would grow into a crumpled mess rather than the huge, smooth cosmos that modern astronomers observe.
Inflation quickly became the leading theory of our cosmic origins. Yet the issue of initial conditions remained: What was the source of the minuscule patch that allegedly ballooned into our cosmos, and of the potential energy that inflated it? Just as a shuttlecock has a diameter of zero at its bottommost point and gradually widens on the way up, the universe, according to the no-boundary proposal, smoothly expanded from a point of zero size.
Entropy increases from the cork to the feathers, aiming an emergent arrow of time. The no-boundary proposal has fascinated and inspired physicists for nearly four decades. The proposal represented a first guess at the quantum description of the cosmos — the wave function of the universe.
The proposal is, of course, only viable if a universe that curves out of a dimensionless point in the way Hartle and Hawking imagined naturally grows into a universe like ours. Hawking and Hartle argued that indeed it would — that universes with no boundaries will tend to be huge, breathtakingly smooth, impressively flat, and expanding, just like the actual cosmos.
The paper ignited a controversy. After two years of sparring, the groups have traced their technical disagreement to differing beliefs about how nature works. Hartle and Hawking saw a lot of each other from the s on, typically when they met in Cambridge for long periods of collaboration. In , Albert Einstein discovered that concentrations of matter or energy warp the fabric of space-time, causing gravity.
Hawking and Hartle were thus led to ponder the possibility that the universe began as pure space, rather than dynamical space-time.
And this led them to the shuttlecock geometry. In the s, Feynman devised a scheme for calculating the most likely outcomes of quantum mechanical events. To predict, say, the likeliest outcomes of a particle collision, Feynman found that you could sum up all possible paths that the colliding particles could take, weighting straightforward paths more than convoluted ones in the sum.
Likewise, Hartle and Hawking expressed the wave function of the universe — which describes its likely states — as the sum of all possible ways that it might have smoothly expanded from a point. 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. 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. Recent mapping efforts actually suggest that the universe is lopsided, with more fluctuations in some areas than in others. Some cosmologists see this observation as supporting evidence that our universe "bubbled off" from a parent universe, in the words of California Institute of Technology researcher Adrienne Erickcek [source: Lintott ].
In chaotic inflation theory , this concept goes even deeper: an endless progression of inflationary bubbles, each becoming a universe, and each of these birthing even more inflationary bubbles in an immeasurable multiverse [source: Jones ].
Still other models revolve around the formation of the pre-Big Bang singularity itself. If you think of black holes as cosmic trash compactors, they stand as prime candidates for all that primordial compression, so our expanding universe could theoretically be the white hole output from a black hole in another universe. A white hole is a hypothetical body that acts in the opposite manner of a black hole, giving off serious energy and matter rather than sucking it in.
Think of it as a cosmic exhaust valve. Some scientists propose that our universe may have been born inside a black hole, and every black hole in our own universe could each contain separate universes as well [source: Choi ].
Long ago, medieval religious philosophers in India taught that the universe goes through an endless cycle of creation and destruction, in which it evolves from an undifferentiated mass unto the complex reality the we see around us, before destroying itself and starting anew [source: Davis ].
Some contemporary scientists have arrived at an idea with striking parallels. They believe that instead of a Big Bang , the universe expands and contracts in a cycle, bouncing back each time that it shrinks to a certain size. In the Big Bounce theory , each cycle would begin with a small, smooth universe that wouldn't be as tiny as the singularity.
It would gradually expand, and become clumpier and more warped over time.
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