Big Bang Theory or can we drop 'theory' now?

[Not Afraid]

Who's Dimsdale?

[scaeagles]

Originally Posted by Moonliner

Not necessarily. You are assuming a universe that is essentially coasting. That does not seem to be the case. As I posted above the "universe" has been shown to be accelerating.

Nope. I am assuming a universe that is not accelerating as quickly as it once did. From what I've read, over the next several billion years, the acceleration will continue to slow to a point where it is not accelarating any longer, and gravity will take over, leading to the "big crunch".

[Alex]

Big Crunch or Eternal Expansion have been the question for a couple decades now but the recent evidence is pointing towads Eternal Expansion and figuring out where the energy for that is coming from is a new Big Question.

[Moonliner]

Originally Posted by scaeagles

Nope. I am assuming a universe that is not accelerating as quickly as it once did. From what I've read, over the next several billion years, the acceleration will continue to slow to a point where it is not accelarating any longer, and gravity will take over, leading to the "big crunch".

Fair enough, but how about this..

You are also assuming that there are no outside influences acting on what us puny humans think is the universe.

[scaeagles]

Interesting.....I thought new theories about the existance of "dark matter" that provides a large portion of the mass to the universe were contributing to thinking in the other direction. As in more mass = higher energy output to continue the expansion = slower accelaration to the point of stopping and reversing.

But to be honest, I do not consider myself an expert or even well read on the subject.

[scaeagles]

Originally Posted by Moonliner

Fair enough, but how about this..

You are also assuming that there are no outside influences acting on what us puny humans think is the universe.

Oh, I agree....I'm not thowing in any of my personal religious beliefs into this whatsoever, as that would certainly take it a bit off topic. Trust me - both in the supernatural realm and in the natural realm there is WAY too much that we have no clue about to make any sort of theory that will last longer than the next important discovery will allow it to. In that way, I agree with ISM wholeheartedly.

[innerSpaceman]

Originally Posted by scaeagles

I agree with ISM wholeheartedly.

I'm going to be using this, completely out of context, for the forseeable future.

[Alex]

Here's an example of the recent evidence for an ever expanding universe (not only that but a universe in which the rate of expansion is increasing).

One of the key things to keep in mind is when discussing the expansion and contraction of the universe you are not simply talking about the movement of matter moving away from the center of the universe but of spacetime itself actually expanding (that is, if you took two galaxies side by side and gave them the exact same movement they would still move apart from each other because the spacetime between them is expanding).

When talking about a Big Crunch it is not just that all matter recondenses in the middle of a now very huge empty space but that all space crunches down into a very small volume, outside of which neither space nor time as we understand it exist.

As for the "speed of light" thing Moonliner mentioned, GD is right that in the way we think about it now the speed of light was much higher in the early moments after the big bang. However, "speed of light" as an applicable concept didn't become relevant until after the four forces (electromagnetic, gravity, strong nuclear, weak nuclear) "condensed" out of the cooling universe aftre the Big Bang. At sufficiently high temperatures these forces "evaporate."

And on multiple big bangs it is possible that there are others in our universe but nothing in the "visible" universe supports the idea of multiple expansions in our spacetime. However, the "visible universe" will never be equal to "the entire universe" in an ever expanding universe so it is always possible that there is contrarian (blue-shifted galaxies, for example) evidence in parts of the universe we'll never be able to see.

There are cosmologies that conjecture beyond our universe that involve multiple (and perhaps frequent) Big Bangs creating other universes. For example, one theory has pieces of spacetime being lost through wormholes at sizes near the Planck constant, these wormholes evaporate and then the lost bit of spacetime creates its own Big Bang creating a new universe, but one that is completely separated and unmeasurable from our own.

But this is another topic (like GD's mechanical thinking thread a couple weeks ago) where I quickly get into territory I'm sometimes just happy to understand the questions being asked, even if I don't understand the answers being provided.

[Alex]

And if interested, Brian Greene's The Fabric of the Cosmos: Space, Time, and the Texture of Reality is a mostly accessible lay account of the issues involved. I strongly recommend it for anybody interested in the topic.

Greene is best known for his book on superstring theory (that was turned into a popular PBS show) called The Elegant Universe.



And of course this is all irrelevant if there is a God because any attempt at figuring out how the universe works is pointless since the rules can be changed at any time and may have changed at any time in the past.

[scaeagles]

I always liked A Brief History of Time by Hawking.