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posted by Fnord666 on Sunday October 27 2019, @12:12AM   Printer-friendly
from the 3-2-1-Universe! dept.

Submitted via IRC for Bytram

Putting the 'bang' in the Big Bang: Physicists simulate critical 'reheating' period that kickstarted the Big Bang in the universe's first fractions of a second

As the Big Bang theory goes, somewhere around 13.8 billion years ago the universe exploded into being, as an infinitely small, compact fireball of matter that cooled as it expanded, triggering reactions that cooked up the first stars and galaxies, and all the forms of matter that we see (and are) today.

Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. During this period, matter -- a cold, homogeneous goop -- inflated exponentially quickly before processes of the Big Bang took over to more slowly expand and diversify the infant universe.

Recent observations have independently supported theories for both the Big Bang and cosmic inflation. But the two processes are so radically different from each other that scientists have struggled to conceive of how one followed the other.

Now physicists at MIT, Kenyon College, and elsewhere have simulated in detail an intermediary phase of the early universe that may have bridged cosmic inflation with the Big Bang. This phase, known as "reheating," occurred at the end of cosmic inflation and involved processes that wrestled inflation's cold, uniform matter into the ultrahot, complex soup that was in place at the start of the Big Bang.

"The postinflation reheating period sets up the conditions for the Big Bang, and in some sense puts the 'bang' in the Big Bang," says David Kaiser, the Germeshausen Professor of the History of Science and professor of physics at MIT. "It's this bridge period where all hell breaks loose and matter behaves in anything but a simple way."

Journal Reference:
Rachel Nguyen, Jorinde van de Vis, Evangelos I. Sfakianakis, John T. Giblin, David I. Kaiser. Nonlinear Dynamics of Preheating after Multifield Inflation with Nonminimal Couplings. Physical Review Letters, 2019; 123 (17) DOI: 10.1103/PhysRevLett.123.171301


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  • (Score: 1, Insightful) by Anonymous Coward on Monday October 28 2019, @04:46AM (2 children)

    by Anonymous Coward on Monday October 28 2019, @04:46AM (#912649)

    This is reversing causation.

    The problem that cosmic inflation sought to solve is that a straight forward big bang doesn't work. If you just look at universal expansion and go backwards until everything's mushed up, as the big bang hypothesis initially held, it fails. Areas in our universe that should not be causally connected in such a scenario, are causally connected. Causally connected just meaning that light's had enough time to get from point A to point B, and thus point A can have a causal effect on point B. Cosmic inflation was a patchwork hypothesis. Well, what we see doesn't match the big bang. However, if we magically send the universe into hyperdrive for a few moments at exactly this time, and then slow it down again at exactly this time, then we could get things to match! And thus cosmic inflation was born.

    So no, reality does not validate cosmic inflation. Cosmic inflation is a hack to 'fix' the big bang hypothesis.

    Cosmic inflation is poor science, but highly regarded. I think the reason there is that without cosmic inflation you have to discard the big bang. And the problem is that there's quite a lot of evidence for the big bang including stuff that was not known about when it was first hypothesized, such as the cosmic microwave background radiation. So something like the big bang very likely did happen. Nonetheless, cosmic inflation is a big part of the reason I turned away from cosmology as a field. It's an extremely critical building block of cosmology, but one that is only supported by the observations it set out to hack a broken hypothesis to get to match. If cosmic inflation is wrong, and there's every reason in the world to think it might be, then the current state of cosmology could effectively be akin to trying to understand planetary dynamics while under the assumption that everything in the universe revolves around the Earth.

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  • (Score: 3, Funny) by aristarchus on Monday October 28 2019, @08:57AM (1 child)

    by aristarchus (2645) on Monday October 28 2019, @08:57AM (#912720) Journal

    If you just look at universal expansion and go backwards until everything's mushed up, as the big bang hypothesis initially held, it fails.

    That is just common sense, and advanced physics, you Coward of Anonymity! Did you not ever notice that once you open a package, and try to re-insert the contents, whether it be socks, or pop-corn, or muckluck, they never all fit neatly back in the way they came out? Same with biologic beings. Birth is a one-way ride. So, you are surprised it fails? Of course it does! Big bangs do no negate the fundamental laws of thermodynamics and packaging!

    • (Score: 0) by Anonymous Coward on Monday October 28 2019, @05:59PM

      by Anonymous Coward on Monday October 28 2019, @05:59PM (#912905)

      That's not quite the problem. It's not the ordering of things but the 'causality' of things. Imagine you shoot out a bunch of stuff from a single point in all directions at the speed of light. After x light seconds, the distance between distant points on the expansion points will be greater than x light seconds. And so it would take time for these points to become causally connected, that would be proportional to their location and the time spent inflating. The problem we have in our universe is that areas that should not be causally connected (in other words, even at the speed of light nothing should have been able to get from point 1 to point 2) are causally connected.

      And there's no good explanation for this. Cosmic inflation was a patch-work solution. It says "Well what really happened is the universe expanded far faster than the speed of light for a bit as the big bang was banging, and then it slowed back down again." Instead of actually trying to resolve through any logic or principle why things that should not be causally connected are, it simply applied an ad-hoc patch to the big bang to make it fit what we already knew to be true. Quite a depressing realization that even the "hard sciences" are playing similar games as those in the social sciences now a days.

      In my opinion it would be far more productive to simply leave such things as open unexplained questions rather than applying ad-hoc patches to retrofit falsified hypotheses. The big reason is that there is every reason to think that cosmic inflation might be wrong. But as it has become a foundation of cosmology it now has a substantial amount of further work built atop it. And so if and when it's falsified it stands to set science back many decades or even centuries. Indeed the worse option is that it's wrong, but not even able to be cleanly falsified. Then cosmology could ultimately just hit a dead end in the case where it is building upon a broken foundation.

      We probably are substantially more intelligent, owing in part to genetic selection and in part to environmental factors (negligible malnutrition in formative years, negligible lead exposure in formative years, etc) than we were in the past. But I suspect the outliers probably have not changed all that much. In other words average Joe today is much smarter than average Joe of 300 years ago. But I doubt Einstein was really all that much more intelligent than Newton, and one might even argue that perhaps some individual such as Aristotle may have been the most naturally intelligent individual to ever grace this Earth. The concern then is what was the hold up...? And I think when we look back at science in the past we can see that they got clogged up on incorrect theories. Astrology draws so many parallels to psychology of today. And in times past geocentricism seems analogous to the way we are treating an increasingly large number of hypotheses. It fits reality enough that it keeps being pushed along by inertia, even though it was always quite a troubled hypothesis.