Big Bang Theory

Usually when discussing the topic, a statement similar to this will surface: “…in the moments before the big bang all matter in the universe was contained to an area aproximately the size of an atom.” This statement in itself is hard to imagine. My question is; if the event is cyclical, why would ALL matter need to be in this location before the the ensuing explosion takes place? Couldn`t some straggling far reaching matter be outside the “atom” and thus be left out of the whole event? This would seem like a likely scenario. Would not chaos possibly come into play? Also how would the relationship between time/gravity be affected if all matter was not contained before the big bang?

There can be no stray matter. The “atom” as you put it, is so dense, and so massive nothing, absolutely nothing can escape its pull. So no, its not a likely scenario. If what you are referring to is a theoretical “big crunch”, as the Universe begins to collapse in upon itself, the centre begins to gain density and mass, thus continually strengthening its pull on all outward matter. To the point that any “stragglers” is impossible.

As for the relationship between time/gravity – In the “moments before the big bang” time and gravity did not exist. Nor did they exist as we know them moments after the big bang.

Sorry to step on Eidolon’s answer but…

Whuck, if you look at your sources on the Big Bang, they should read “…in the moments just after the big bang began…”

If it doesn’t say this, get some better books.

Now, on to why… This is hard to visualize, but… Try not to imagine the big bang happening as a tiny point in the large open space of the existing universe. If space was the size it is today, the big bang would immediately collapse into a massive blackhole and that would be the end of it. The real rules get odd when you take into that the big bang was the entire universe. The expanding ball of energy and particles created space as it went. The space was not there already to expand into.

On to one of Eidolon’s specific statements: "as the Universe begins to collapse in upon itself, the centre begins to gain density and mass, thus continually strengthening its pull on all outward matter. To the point that any “stragglers” is impossible. "

The real reason that stragglers would be impossible in the big crunch idea is not due to the gravity of the central mass. It would be because space itself, the very universe, is getting smaller and shrinking toward zero size. The only way to avoid being involved would be to actually step “outside” the universe as we know it and watch from the outside, which doesn’t seem very likely unless we find another large scale space dimension and figure out how to travel in it.

As mentioned there is no ‘before’ the Big Bang…at least not as we ubderstand the concept. Time itself began at the Big Bang hence there is no ‘before’.

Likewise, there is no ‘outside’ the Big Bang singularity. If there is it is absolutely meaningless to us. You can speculate the Big Bang singularity floated in a sea of cream cheese if you like…it’s as useful an answer as anything else you can come up with.

As for the Big Crunch the current belief is it will not happen. The Universe will continue to expand forever till eventually the Universe is one big, generally empty, cold cold place (heat death). There is a new theory out there postulating ‘membranes’ (or ‘branes’) in which multi-dimensional membranes that contain Universes unto themselves collide every few trillion years or so thus possibly providing a mechanism for renewal of our Universe (if anything were alive at such an occurence this would almost certainly destroy it). This has been discussed on these boards before so you might try a search if you’re interested.

There is also some evidence that gravity may not perfectly follow the inverse square law at VERY large distances. This could reverse this thinking, but WaM is right in that the most supported idea is that their isn’t enough matter in the universe to cause a big crunch.

If gravity falls off slower than inverse square at very large distances, there just might be enough matter to do the trick.

The theory positing this is very preliminary, and so far is inconsistent with relativity (a MAJOR stumbling block), but we’ll see what happens in the next few years as more data is collected and the guys forwarding this theory put more work into it.

I think Im missing something so forgive me here. In order for the big bang to have occurred would all matter have had to crunch together? Why isnt an outward explosion possible with only half the matter crunched together or three quarters of the matter or any fraction you choose? Why must ALL matter be involved. I understand the immense gravity involved and the speed at which this may occur, but this is all relative to whatever is happening at the time. Why can`t an outward explosion occur half-way into the crunch? Must all matter be incorprated? Are there any models that suggest this?

Understand the Universe itself is what is involved here. The ‘balloon’ is shrinking so you can have all the explosions you want inside the balloon but it doesn’t change the fact that the balloon itself is getting bigger or smaller. Everything happens within the balloon. When the balloon shrinks to zero (or nearly so) size that is your ultimate Big Crunch.

[sub]NOTE: The balloon analogy isn’t perfect when thinking about this stuff but I think it’s close enough for these purposes.[/sub]

This may lead to the question: What are the odds that the balloon would have shrunk to zero? Or that all matter was at the same point at the time of the big bang? Don`t we premise alot of our universe expansion theories on one all encompassing big bang?

The odds of everything being together (if this idea is correct) is 100%. That is the point, there is no other place to be.

This is an oversimplifications, but… picture the grid of space being inside a closed box, this box would be the actual universe. Everything must happen/exist inside that box. If the box is only 1 inch on a side, all the matter and energy in the whole universe is/must be squeezed into that single cubic inch. There is no other where to be.

At the first moment of the big bang, it is supposed that the whole universe, the very diffinition of space was microscopic and quickly inflated giving the stuff inside the elbow room they have today over time.

The documentaries often fail to mention that in the moments after the big bang all space in the universe was also contained in an area approximately the size of an atom. It’s tough to have chunks floating about outside the bang when there is no detectable “there” there.

Can there be more than one box? Can we have parrallel universes? What would rule this out? As I think about this, if there were two “boxes” relativity would place them right next to each other and that would be impossible. But what about three?

As far as we know, there is nothing that would rule out other universes.

But, the concept of right beside each other just doesn’t apply.

There is no concept of position (at least in the manner that you are familiar) outside of the box/universe.

We do premise a lot of our theories on the Big Bang. Note the use of the word ‘theory’ here. The Big Bang theory is only one of many and is the most widely accepted but it is not agreed upon by all scientists and may certainly be completely wrong. Indeed, the term ‘Big Bang’ was coined as a derogatory term by a guy (I forget his name but I know he died recently) who hated the concept. Ironically the name stuck.

As to shrinking if the Universe is headed for collapse in a Big Crunch then nothing I can think of will stop it. So the odds of shrinking to zero (or nearly zero) size are 100%. Of course, as mentioned, the Universe may not collapse on itself at all but may continue to grow forever. That’s still an open question but as of today the ‘grow forever’ theory is in favor.

If the grow forever theory is the favorable one today, how do we explain the conditions for the big crunch, the one that precipitated the big bang?
If matter had previously collapsed in the big crunch to cause the big bang why do we think the grow forever theory holds water?

Who says there was a Big Crunch prior to our Big Bang? There is simply no way for us to look back further than the Big Bang singularity. In fact, we can get close (tiny fractions of a second) to the Big Bang itself but our understanding of physics utterly breaks down at the singularity itself (or actually some fractions of a second post Big Bang). Maybe this is the first time the Big Bang ever happened. We simply cannot say with any certainty. In fact, if a Big Crunch did happen we couldn’t say that a Big Bang must again necessarily follow. It is aethetically pleasing (to me at least) to think that our Universe goes through an endless cycle of birth, death and re-birth like the mythical Phoenix but I wasn’t consulted on what I liked when the Universe was created unfortunately.

There is no requirement that a big crunch happened before the big bang.

Big bang stands alone. The big crunch is an extension to the big bang theory that comes up for a way to have a succession of big bangs, but it is not required for the big bang to hold true.

So, now what caused the big bang to happen? Any of the current theories that have any significant amount of evidence that supports them simply can’t answer this question at all.

Relativity and the Quantum Physics standard model pretty much quit working when you roll the clock back to Big Bang + very very small amounts of time. At Big Bang + 0 time, you have an uncalculable mess, so we just don’t know.

Scotth - If we assume there are other universes, cycling as ours does, is it possible that they may have broken off from one central explosion some time in the past. I think no, because they would have had to break away faster than the speed of light. Does this make sense?

What if, on the other hand, a cluster of matter on the outskirts of the universe began collapsing on itself as the rest of the universe began collapsing. Could this smaller cluster crunch and bang seperately from the larger? Theoretically of course.

Faster than the speed of light? That is the problem… the speed of light has no meaning as far as we know outside our universe or between universes if others exist.

Speed can only be measured by comparing relative position. Outside the universe, there is no relative position. There is no speed, there is no distance.

Space as you concieve it is not help to exist outside the universe. With no space, there is no such thing as speed, distance or travel.

If there are/were other universes I don’t know how we would ever know it.

“I think no” the NO was intentional.

So I do agree with what you said. Thanks for the short lesson.

I think you are asking if one Universe could be nested within another Universe. Honestly I have no idea but my guess (for no decent reason…just a gut check) would be no…you cannot do this. Of course the Universe is a strange place…make for good sci-fi (isn’t this what everyone was after in the movie Men in Black?).

As to going faster than the speed of light scotth got most of it. As an FYI there is a theory called Inflationary Theory that speculates that our own universe underwent a faster than light speed expansion in the very early phases post Big Bang. Inflationary Theory seems to resolve a number of observations of our own universe so it is fairly popular today but again is just a theory and by no means universally accepted. This doesn’t bear on your multiple universes but shows that faster than light things may indeed occur.