Pondering the Big Bang

[AstroGuy]

Hi all,

:question: I've been doing a lot of thinking regarding this event. I for one subscribe to the Big Bang Theory. I also subscribe to the Big Crunch Theory also. My Question is: How many times has our universe banged and crunched, and is there a way we could find out using Astronomy and Science? Anybody seen any articles or have any theories regarding this phenomena?

[CraigS]

Hi Eugenio:

Sounds like you actually subscribe to the oscillating universe concept .. Bang .. Crunch .. Bang .. Crunch .. etc, etc. Unfortunately, this can't easily be explained in terms of the Second Law of Thermodynamics, (temperature, pressure etc, balance out in an isolated physical system), due to the rise in entropy and ultimate heat death. Ie: there ain't no such thing, (in the real world), as a perpetual motion machine .. (for good reasons) !

The Cyclic universe theory overcomes this however, as it is based on String/M-Theory 'branes', which moderates entropy.

Cheers

[mjc]

Craig

Any chance you can elaborate - I personally don't see the difference between an oscillating universe and a cyclic one.

I understand that the second law of thermodynamics decrees that temperature tends to equilibrium - and I feel that that is synonymous with increased entropy (disorder).

If the universe enters a stage where it contracts back to a singularity then I see no reason why this second law of thermodynamics ( and increasing disorder - increasing erosion of structure) should be violated. It's the the next phase which raises questions.

At the singularity laws of physics (as we know them - or of what I understand them to be) break-down. Hence any subsequent re-expansion of the universe could start out highly ordered and no violation of our understood laws has taken place.

I'm completely beyond my competency level here - but that is how I see this.

With regards to Astroguy's (Eugenio) query - I don't think we can know - I think that we should assume an infinite number of times as anything else would raise the question of why any particular "start" time was so special and unique.

Mark C.

[CraigS]

Hi Mark;

The traditional oscillating universe models are closed models, and are thus still constrained by the second law (entropy can only increase). This implies that each successive cycle gets longer and bigger. If you run this backwards in time, it ends up in a Big Bang. So which is it .. an initial BB with increasing longer and larger cycles, or an infinitely oscillating universe ? Externally provided energy would sort out this dilemma .. so an oscillating model requires Dark Energy which, for all intents an purposes, is externally added energy (ie: a fudge factor added).

(By the way .. I didn’t say the 2nd Law was violated by an oscillating model).

In the cyclic models, two parallel M-branes collide in higher dimensions. Our observable universe is on one of them. A contraction phase is kicked into a violent expansion (or BB) whenever there is a collision. The expansion during each cycle, prevents entropy from building up. No-one really understands the collision process, nor the origin of the forces that causes them to collide - mysterious quantum fluctuation forces between the branes, I believe.

Subtle differences .. one bounded by the 2nd Law, the other not necessarily bounded because no-one really understands it ! :lol:
:)

Cheers

[AstroGuy]

mmmmmmm........Interesting......you mention that:

"The traditional oscillating universe models are closed models, and are thus still constrained by the second law (entropy can only increase). This implies that each successive cycle gets longer and bigger."

Should not each succesive cycle emit radiation which is now beyond our/the known physical universe? (energy that cannot be reclaimed before the next cycle begins anyway, especially nutrino energy), and if so, then should the energy expelled by such radiation deplete the original matter used to create the universe? and if so, should not the cycles be getting smaller having less energy to expand on each cycle? therefore, cycles will get smaller and shorter?

If the energy/radiation expelled during each cycle's initial "Bang" is not reclaimed quick enough before the next cycle is created, it could be reclaimed in succesive cycles adding a kind of harmony (not the peace kind, although it would be good if it were :) ) rather than a fixed or slightly changing cycle frequency? I think If these specific harmony's exist they could tell us how old we really are.

Thanks Craig and Mark, you raise some interesting views on this matter and got me thinking! i will ponder this some more:question: Thanks!

[mjc]

Thanks for the clarification Craig.

Astroguy,

The following might have some relevance to your enquiry:
http://blogs.discovermagazine.com/80beats/2010/11/29/have-physicists-found-echoes-from-before-the-big-bang/

There were two concurrent threads on this earlier in the forum:
http://www.iceinspace.com.au/forum/showthread.php?t=68808&highlight=penrose
http://www.iceinspace.com.au/forum/showthread.php?t=68543&highlight=penrose

Mark C.