How can there be no beginning

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. And summing over universes with real values of lapse leads to the wildly fluctuating, physically nonsensical solution. He and Hartle analyzed the issue of the contour of integration in He and his colleagues argue that, in the minisuperspace case, only contours that pick up the good expansion history make sense.

Imaginary numbers pervade quantum mechanics. To team Hartle-Hawking, the critics are invoking a false notion of causality in demanding that lapse be real.

At some level, there's a fundamental unit of space-time , according to this theory. Bento and his collaborators used this causal-set approach to explore the beginning of the universe.

They found that it's possible that the universe had no beginning — that it has always existed into the infinite past and only recently evolved into what we call the Big Bang. Quantum gravity is perhaps the most frustrating problem facing modern physics. We have two extraordinarily effective theories of the universe: quantum physics and general relativity.

Quantum physics has produced a successful description of three of the four fundamental forces of nature electromagnetism , the weak force and the strong force down to microscopic scales. General relativity, on the other hand, is the most powerful and complete description of gravity ever devised.

But for all its strengths, general relativity is incomplete. In at least two specific places in the universe, the math of general relativity simply breaks down, failing to produce reliable results: in the centers of black holes and at the beginning of the universe. These regions are called "singularities," which are spots in space-time where our current laws of physics crumble, and they are mathematical warning signs that the theory of general relativity is tripping over itself.

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By using this site, you agree to our Guidelines and Privacy Policy. General Chat Search In. Sign in to follow this Followers 0. How can something have no beginning or end? Recommended Posts. Sobend Posted March 17, Share this post Link to post Share on other sites. Guitarguy Micael Fatia Renegaderp Does Death have a beginning or an ending? The Skiller Posted March 24, Is there any example of anything that has no beginning and no end? Posted March 25, Posted March 26, edited. Do we know that time has no beginning or end though?

Fatalysm Posted March 26, There are days, many of them, when I resent the size of my unbounded set. I want more numbers than I'm likely to get, and God, I want more numbers for Augustus Waters than he got. But, Gus, my love, I cannot tell you how thankful I am for our little infinity. I wouldn't trade it for the world. You gave me a forever within the numbered days, and I'm grateful. Of course, there is a bigger infinite set of numbers between 0 and 2, or between 0 and a million.

Some infinities are bigger than other infinities. A writer we used to like taught us that. But this severely alters our conceptions of how the Universe began. Earlier, I presented you a graph of how the size or scale of the Universe evolved with time. The graph displayed the differences between how the Universe would expand if it were dominated by matter in red , radiation in blue , or space itself such as during inflation, in yellow at early times.

However, I wasn't completely honest with you in displaying that graph. You see, I omitted something in the earlier graph, because I truncated it at a positive, finite time. In other words, I stopped the graph before we reached a size of zero.

That would have been where the original idea of the Big Bang occurred. But in an inflationary Universe, you only asymptote to a size of zero; you never reach it.

But in an inflationary scenario yellow , we never reach a singularity, where space goes to a singular state; instead, it can only get arbitrarily small in the past, while time continues to go backwards forever. The Hawking-Hartle no-boundary condition challenges the longevity of this state, as does the Borde-Guth-Vilenkin theorem, but neither one is a sure thing. Like many great discoveries in science, this leads to a slew of delightful new questions, including:.

The different ways dark energy could evolve into the future. Remaining constant or increasing in Under either of those two scenarios, time may be cyclical, while if neither comes true, time could either be finite or infinite in duration to the past.

Observationally, we don't know the answer to any of these questions. The Universe, as far as we can observe it, only contains information from the final 10 seconds or so of inflation.

Anything that occurred prior to that — which includes anything that would tell us how-or-if inflation began and what its duration was — gets wiped out, as far as what's observable to us, by the nature of inflation itself.

Theoretically, we don't fare much better. The Borde-Guth-Vilenkin theorem tells us that all points in the Universe, if you extrapolate back far enough, will merge together, and that inflation cannot describe a complete spacetime.

But that doesn't necessarily mean an inflating state couldn't have lasted forever; it could just as easily imply that our current rules of physics are incapable of describing these earliest stages accurately. We do not have enough information in our Universe, today, to know which of these possibilities is accurate.

Even though we can trace our cosmic history all the way back to the earliest stages of the hot Big Bang, that isn't enough to answer the question of how or if time began.

Going even earlier, to the end-stages of cosmic inflation, we can learn how the Big Bang was set up and began, but we have no observable information about what occurred prior to that. The final fraction-of-a-second of inflation is where our knowledge ends. Thousands of years after we laid out the three major possibilities for how time began — as having always existed, as having begun a finite duration ago in the past, or as being a cyclical entity — we are no closer to a definitive answer.

Whether time is finite, infinite, or cyclical is not a question that we have enough information within our observable Universe to answer. Unless we figure out a new way to gain information about this deep, existential question, the answer may forever be beyond the limits of what is knowable. This is a BETA experience.