Big Bang Mystery: Where Did the Explosion Take Place?

[QAZI]

If there were no Space-Time before the Big Bang, then where did that explosion took placed?

 

[JaredJames]

There was no explosion. The big bang did not explode.

Perhaps there should be a sticky on this mentors? There's at least one of these threads a week.

 

[mjacobsca]

Current theories suggest that the Big Bang was a rapid expansion of the FABRIC of space, and not an explosion at all. After the initial expansion reached a critical phase, the energy from the expansion "froze" into normal matter, consisting of matter and antimatter, at which point the two types of matter annihilated each other, leaving only regular matter and pure energy in the form of photons. The whole process may have been completely silent for all we know. Obviously, I am simplifying the Big Bang completely, but hopefully you get my point. There is lots to read up on in this forum!

 

[QAZI]

Current theories suggest that the Big Bang was a rapid expansion of the FABRIC of space, and not an explosion at all. After the initial expansion reached a critical phase, the energy from the expansion "froze" into normal matter, consisting of matter and antimatter, at which point the two types of matter annihilated each other, leaving only regular matter and pure energy in the form of photons. The whole process may have been completely silent for all we know. Obviously, I am simplifying the Big Bang completely, but hopefully you get my point. There is lots to read up on in this forum!

hmm. where did that expansion took placed then ?

 

[QAZI]

There was no explosion. The big bang did not explode.

Perhaps there should be a sticky on this mentors? There's at least one of these threads a week.

yup.

 

[Cosmo Novice]

hmm. where did that expansion took placed then ?

That expansion did not take place somewhere:

The Big Bang (BB) was the beginning of the Universe (U).
U = "the totality of everything"
The totality of everything = matter (stars and planets etc), space (the vacuum of space between matter), time, and energy in all its forms.

Therefore at the BB (Actually we are talking about >planck time as only t>0 is meaningful t=0 is a singularity so there is no current theory for then) everything began. Geometrically space/time (the space/time continuum that is our U) began in all points, as essentially you cannot define space or time outside of our current space/time manifold. So the BB didnt begin at a "point in space" as prior to the beginning of existence there was none.

The expansion takes place in all points in the fabric of space/time, space/time is expanding in all points isotropically with only local variance. An expansion can happen without need to expand "into" something. You need to take away this notion of "empty space" or a "void" for this to become clearer. Essentially reality expanded.

Does this make things a little easier perhaps?

 

[MJA]

Did the big bang make any sound?

=
MJA

 

[bcrowell]

If there were no Space-Time before the Big Bang, then where did that explosion took placed?

We have a FAQ on this topic: https://www.physicsforums.com/showthread.php?t=506991

Did the big bang make any sound?

There were sound waves in the early universe, but you don't want to imagine them as sound waves spreading out from a point, because there was no specific point where the Big Bang happened.

-Ben

 

[marcus]

...
The expansion takes place in all points in the fabric of space/time, space/time is expanding in all points isotropically with only local variance. An expansion can happen without need to expand "into" something. You need to take away this notion of "empty space" or a "void" for this to become clearer. Essentially reality expanded.
...

That's well put ("reality expanded"). Experienced from the inside of what is expanding (not pictured from the "outside" because there is no "outside") it just refers to distances increasing--according to a regular pattern.

So you say "get rid of the notion" of some surrounding context. The picture of the U expanding within a surrounding context is contradictory. All existence can contract and it can expand---meaning a pattern of distances decreasing, or increasing, experienced by an observer inside. As you say, when we are talking about the U, which is all existence, there is no outside. Good.

So Cosmo Novice I want to suggest that you have a look at this May 2010 review paper by Abhay Ashtekar:
http://arxiv.org/pdf/1005.5491

Here is the one-page summary http://arxiv.org/abs/1005.5491 but I hope you have a look at the PDF of the whole thing. Just read what is currently comfortable for you. I think some will be. Pick out the understandable parts that are not too technical.

He refers to the various models of cosmology which have been constructed over the years in an attempt to resolve the singularity (where classical 1915 General Relativity breaks down.)

There is a two-week international conference going on at Zurich now ("Quantum Theory and Gravitation") where Ashtekar gave the main cosmology talk last week. Here is the programme with links to slides PDF just in case anyone is interested:
http://www.conferences.itp.phys.ethz.ch/doku.php?id=qg11:programme
The conference gathers together people from the several main approaches to quantum gravity (string, loop, ...several others) and cosmology.

 

[Cosmo Novice]

That's well put ("reality expanded"). Experienced from the inside of what is expanding (not pictured from the "outside" because there is no "outside") it just refers to distances increasing--according to a regular pattern.

So you say "get rid of the notion" of some surrounding context. The picture of the U expanding within a surrounding context is contradictory. All existence can contract and it can expand---meaning a pattern of distances decreasing, or increasing, experienced by an observer inside. As you say, when we are talking about the U, which is all existence, there is no outside. Good.

So Cosmo Novice I want to suggest that you have a look at this May 2010 review paper by Abhay Ashtekar:
http://arxiv.org/pdf/1005.5491

Here is the one-page summary http://arxiv.org/abs/1005.5491 but I hope you have a look at the PDF of the whole thing. Just read what is currently comfortable for you. I think some will be. Pick out the understandable parts that are not too technical.
.

Thanks Marcus - Sometimes I think it is easier for a novice to explain these things - as I recently struggled to grasp them.

Thanks for the reading material - I will definitely have a look when I have a bit more time on my hands. Currently I think I have a decent conceptual understanding on the BB so it might be worthwhile me doing a bit of reading and maybe delving into the mathematics a little.

Thanks again, Cosmo.

 

[bcrowell]

Thanks Marcus - Sometimes I think it is easier for a novice to explain these things - as I recently struggled to grasp them.

Like Marcus, I often really like your explanations.

-Ben

 

[leonstavros]

This idea of the BB not banging will not go away. Where did the rules come from? Theory says from some condition that produces universes with different rules and our universe has the rules that we know. But doesn't that mean there was time before our time? Can time exist without space? I don't think so. So space/time existed before, therefore our universe expanded into a previous space/time. I just don't buy the idea of our universe is not expanding into some other space/time.

 

[bcrowell]

This idea of the BB not banging will not go away. Where did the rules come from? Theory says from some condition that produces universes with different rules and our universe has the rules that we know.

This is true for some theories but not others (such as general relativity). Can you point us to a specific, professionally researched theory that you have in mind here?

So space/time existed before, therefore our universe expanded into a previous space/time.

Your "therefore" doesn't follow from the assumption. There are theories in which spacetime existed before the Big Bang, but according to which the universe did not expand into a previously existing spacetime. If you think there is a professionally researched theory in which our universe did expand into a previously existing spacetime, please post a reference to a scientific publication, preferably in a peer-reviewed journal.

 

[JDoolin]

If there were no Space-Time before the Big Bang, then where did that explosion took placed?

There's actually no conflict, since the explosion takes place at the moment of the Big Bang, or after, but not before.

Time and space before that event is not necessary. It's kind of a unique event in history that may or may not have a cause.

I think of it kind of like a function that has a domain of (0,infinity). You plug in ln(0) or ln(-1) you just get a math error. That doesn't mean ln is a bad function. It just means that it doesn't have any answer for t<0.

Are there "models" of the universe that go back forever? Of course. In most cases, those are called steady-state models. It's just that those theories are really hard to justify given what the astronomers are seeing.

 

[marcus]

Are there "models" of the universe that go back forever? Of course. In most cases, those are called steady-state models...

Haven't heard much about steady state models lately, though. I wouldn't call them typical of today's models that go back forever.

This search finds 242 quantum cosmology papers written 2009 or later:
http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=dk+quantum+cosmology+and+date+%3E+2008&FORMAT=WWW&SEQUENCE=citecount%28d%29

Most are about models that go back in time before bang (don't suffer singularity) and are not steady state. The problem now is to devise ways to *test* the new singularity-free cosmo models.

I think steady state kind of dropped out of the running 50 years ago like around 1960 give or take a few---so it doesn't have to be brought up in this context AFAICS.

 

[narrator]

I think, for the novice (like me ), an entry level explanation is required.

From my understanding, causality is a paradigm of our current expectations of how things work. But at or around t=0, the rules were nothing like we know them (in the novice sense).

When we boil the kettle or hit something with a hammer or design a load bearing beam or ignite fuel in an engine cylinder, we know roughly what to expect because all these reactions are within the realm of our experience and our rules.

As a novice, I can intellectually comprehend the reactions inside a sun, but I have difficulty visualizing it all. Yet it's still relatively within the realm of experience and understanding.

But when you stuff all the contents of the whole universe into one tight little package, the temperatures and pressures are so foreign to our reality that as a novice we make the mistake of trying to interpret it from our usual paradigms. It ain't so.

At that level of compaction, the rules do not resemble anything we laymen can conceive, and have to resort to a mathematical interpretation, and trust those who have done the modelling and the peer review to have the best idea of it that we can currently offer.

The closer you go to t=0, the weirder it gets. When you allow that the rules were nothing like your experience tells you, then the fog begins to clear.

Myself, I still wonder about t<0, but I've resolved this with two possibilities. 1) There was something before t=0, but it could have been anywhere from something like our current reality to something even weirder (lol), or 2) There was nothing before the BB because the notion of any before and after, like time itself, was created along with the BB.

One of the problems we novices have is that if it doesn't fit our understanding, then we're tempted to doubt those who have done the science - which amounts to doubting several million man-hours spent researching and challenging each other's research in an established process that has proven itself. Challenge is a good thing - it's part of science - but understanding is the first stepping stone.