Putting the “bang” in the Big Bang - MIT theoreticians propose the "reheating" period

[gary]

In a press release today by MIT, Jennifer Chu describes theoretical
work being done there to try and bridge the gap between the brief
inflationary period and the Big Bang itself.

The MIT theoreticians are referring to this intermediate stage as the
“reheating” period that kickstarted the Big Bang in the universe's first
few fractions of a second. They have performed computer simulations.

Originally Posted by Jennifer Chu, MIT

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.”

Kaiser and his colleagues simulated in detail how multiple forms of matter would have interacted during this chaotic period at the end of inflation. Their simulations show that the extreme energy that drove inflation could have been redistributed just as quickly, within an even smaller fraction of a second, and in a way that produced conditions that would have been required for the start of the Big Bang.

Originally Posted by Jennifer Chu, MIT

Kaiser and his colleagues attempted to work out what the earliest phases of reheating — that bridge interval at the end of cosmic inflation and just before the Big Bang — might have looked like.

“The earliest phases of reheating should be marked by resonances. One form of high-energy matter dominates, and it’s shaking back and forth in sync with itself across large expanses of space, leading to explosive production of new particles,” Kaiser says. “That behavior won’t last forever, and once it starts transferring energy to a second form of matter, its own swings will get more choppy and uneven across space. We wanted to measure how long it would take for that resonant effect to break up, and for the produced particles to scatter off each other and come to some sort of thermal equilibrium, reminiscent of Big Bang conditions.”

The team’s computer simulations represent a large lattice onto which they mapped multiple forms of matter and tracked how their energy and distribution changed in space and over time as the scientists varied certain conditions. The simulation’s initial conditions were based on a particular inflationary model — a set of predictions for how the early universe’s distribution of matter may have behaved during cosmic inflation.

The scientists chose this particular model of inflation over others because its predictions closely match high-precision measurements of the cosmic microwave background — a remnant glow of radiation emitted just 380,000 years after the Big Bang, which is thought to contain traces of the inflationary period.

Full press release here :-
http://news.mit.edu/2019/putting-bang-in-big-bang-1025

[xelasnave]

Thanks Garry I love big bang stuff...
I heard yesterday yesterday via YouTube a qualified guy say the universe was 250 times larger than the observable universe which is approx 95 billion light years diameter...so I don't know if he means 250 times greater diameter or 250 times as much stuff.
This is such a lot of stuff. I can not see how all of it could fit in a shoe box. .any views?
Alex

[morls (Stephen)]

This may be a silly question, but does the Big Bang theory postulate that all the matter that is - and ever will be - in the universe has been in existence since the very beginning, albeit in different states of being?

[gary]

Originally Posted by morls

This may be a silly question, but does the Big Bang theory postulate that all the matter that is - and ever will be - in the universe has been in existence since the very beginning, albeit in different states of being?

Hi Stephen,

Indeed, the Big Bang theory postulates that all matter originated at that
instant, starting from a singularity.

One must also be mindful of the matter/energy equivalence through
E=mc2. That is seen most dramatically when stars fuse matter, some
of which gets converted into energy.

It is believed that less than 400,000 years after the Big Bang, the first
hydrogen and helium atoms formed when electrons started to become
bound in orbits to nuclei.

But the accounting doesn't quite add up. Approximately 26% of all
matter is believed to consist of so-called "dark-matter" and 70% of all
energy to be so-called "dark-energy".

The "dark" here meaning nobody really knows what it is.

So the visible universe is possibly only 4% of the total universe.

The puzzle over what "dark matter" and "dark energy" are is one of
the deepest mysteries in science today. Suffice to say, many scientists,
engineers and technicians are actively involved in a competition
to be the one that makes the breakthrough discovery.

When you consider how much of the puzzle we have worked out since
Edwin Hubble in 1923 where before that it was believed the Milky Way
was all there was, then we have come along way in our understanding
in a short amount of time.

[morls (Stephen)]

Thanks Gary,
While I find that I can understand basic principles of the Big Bang theory, I'm a long way from fully comprehending the idea that all matter originated in that one instant.

At the moment I'm grappling with a notion, which may be mistaken, that space is created through expansion, rather than matter expanding into empty space. It is hard to understand there is no "outside" into which space expands. This metaphor probably doesn't make sense...

[gary]

Originally Posted by morls

Thanks Gary,
While I find that I can understand basic principles of the Big Bang theory, I'm a long way from fully comprehending the idea that all matter originated in that one instant.

At the moment I'm grappling with a notion, which may be mistaken, that space is created through expansion, rather than matter expanding into empty space. It is hard to understand there is no "outside" into which space expands. This metaphor probably doesn't make sense...

Hi Stephen,

Indeed space itself was created but don't worry too much, nobody can
visualise what that must have been like, especially if you try and visualise
it looking at the singularity from the "outside".