Big crunch

[copperstream]

After several years will the universe end in a small particle which is called big crunch?

[Klaynos]

This is one of the possible ends of the universe, of course we don't know what will happen at the very end of a big crunch scenario, it's possible it'd cause another big bang, we just don't know.... There are other hypothesis about the end including heat death... Have a look on wp about it.

[swansont]

mod note: the variable G conjecture has been moved to speculations. Any further discussion of it should take place there

 

http://www.scienceforums.net/forum/showthread.php?t=33036

[Graviphoton]

There is no definate value, only approxamtions. One is 45 billion years. Tipler has one that calculates trillions of years

[mooeypoo]

I'm not sure, but isn't the entire speculation about dark energy pointing out towards the possible "neverending expansion" of the universe? I know those are two competing theories, I'm just not sure where the speculations lead atm... anyone?

[Graviphoton]

Mooey is 99% correct. The universe, according to carefull calculations, finds overwhelmig evidence that our cosmoc is indeed... open...

[Klaynos]

But we don't really know until we know wtf dark matter is and what the mechanism causing dark energy is. So it's still a big unknown.

[mooeypoo]

But we don't really know until we know wtf dark matter is and what the mechanism causing dark energy is. So it's still a big unknown.

 

Oh, yes, I know, I'm just asking where the "majority" of the assumptions lead at the moment.. Which is considered more plausible?

[BumFluff]

The cyclic universe theory (big crunch) has continued to be updated as new discoveries are being made. Dark energy is thought by those that support this theory to be a type of energy that will eventually diminish and gravity will take over beginning the big crunch.

 

Another theory, spelt something like ekpyrote, theorizes that two branes (part of string or M-theory) will eventually coalesce and the cyclic universe will begin over again.

[lucaspa]

But we don't really know until we know wtf dark matter is and what the mechanism causing dark energy is. So it's still a big unknown.

 

Doesn't matter. The data is clear that the expansion -- by whatever cause -- is accelerating. The expansion is such that the gravity of the universe will never be able to slow it down and bring all the matter back together to a Big Crunch. This is a one way trip.

 

The cyclic universe theory (big crunch) has continued to be updated as new discoveries are being made. Dark energy is thought by those that support this theory to be a type of energy that will eventually diminish and gravity will take over beginning the big crunch.

 

It's already too late for that. Not enough matter to make enough gravity. If dark energy stopped today, the universe would continue to expand forever.

 

Another theory, spelt something like ekpyrote, theorizes that two branes (part of string or M-theory) will eventually coalesce and the cyclic universe will begin over again.

 

Ekpyrotic is different. You have a 5 D universe in which 2 4D branes sit. One of the branes sheds a brane that floats toward the other one. When those 2 branes collide the 4 D universe is wiped out but a new 4 D universe comes into being. Not exactly "cyclic". The acceleration of expansion is interpreted as moving toward that new brane.

 

Of course, ekpyrotic depends on M Theory, and M Theory is in trouble.

[Ladeira]

I'm not an expert at all...

But I think that we're only seeing a way.

As you can imagine an elastic. We're seeing it in expansion, but sometime (in the future) it might torn or regret (when the universe can't expand more).

I think Big Crunch is a good theory.

[Risingashes]

lucaspa can such readings really be relied upon based on current technology scope limitations?

 

I'll admit relative ignorance when it comes to methods of measuring the rate of expansion: would you be able to direct me to any articles or studies that attempt it?

[Royston]

lucaspa can such readings really be relied upon based on current technology scope limitations?

 

I'll admit relative ignorance when it comes to methods of measuring the rate of expansion: would you be able to direct me to any articles or studies that attempt it?

 

To give you some background, accelerated expansion was discovered, by Adam Reiss and his team, with the first article published in 1998 in the Astrophysical journal. So I'd start your search there.

 

The method involves observing Type 1a supernovae, for the obvious reason that they're incredibly bright...some have been visible with the naked eye.

 

The basic method, is that you can plot the observed brightness against the Hubble redshift (don't confuse this with the doppler effect, it's not frame dependant) so the y axis would be time...the farther away the object, the further back in time you're looking. Then on the x axis, you have the a measurement of redshift (ie the wavelength of light is stretched.) So, for distant observations at a given time, the less redshift, would mean acceleration. Higher redshifts, would be the opposite...the expansion is slowing down.

 

Here's a thread I started a while ago, that has links to future projects...

 

http://www.scienceforums.net/forum/showthread.php?t=30633

 

The observations tie in and are intrinsic with the Lambda CDM model, so you may want to google that as well. But there are more than enough articles on the subject, hopefully I've given you enough information on where to look.

Edited May 28, 2008 by Snail
EDIT: sorry if that's too brief, but I'm in the middle of an assignment :)

[lucaspa]

lucaspa can such readings really be relied upon based on current technology scope limitations?

 

I'll admit relative ignorance when it comes to methods of measuring the rate of expansion: would you be able to direct me to any articles or studies that attempt it?

 

The data is what it is. Here are some articles. You shoud be able to find all the journals at your public library.

 

5. A Watson, Clusters point to a never-ending universe. Science, 278: 1402, 21 Nov. 1997. Discusses paper that will appear in Astronomy and Astrophysics about the clusters that bend light from distant objects. The model predicts the number of such clusters we should see. With 33% of the critical mass the model predicts 2500 clusters. We see 2300-2700. Up the mass to the critical value and the predicted number drops to 25.

7. J Glanz, Exploding stars point to a universal repulsive force. Science 279:651-652, 30 Jan. 1998. New data indicates the cosmological constant is back.

7a. J Glanz, No backing off from the accelerating universe. Science 282: 1249-1250, Nov. 13, 1998. As the title says, 2 independent and competing groups continue to get data that agrees.

8. G Tarke and S.P. Swordy, Cosmic Antimatter. Scientific American, 278(4): 36-41, April 1998.

10. CJ Hogan, RP Kirshner, and NB Suntzeff, Surveying space-time with supernovae. Scientific American, 280: 46-51, Jan. 1999. Studies indicate that the rate of expansion of the universe is accelerating.

11. LM Krauss, Cosmological antigravity. Scientific American, 280: 52-61, Jan. 1999. discusses cosmological constant to explain accelerating expansion.

4. J Glanz, Microwave hump reveals flat universe. Science 283: 21, Jan 1, 1999. Data on microwave background radiation indicates that universe is flat. Means there must be the cosmological constant. And inflation theory survives.

15. SJ Goldstein, Jr The cosmological constant. [letter] Science 283: 794, Feb. 5, 1999. Attempted critique of using supernovae to measure distance. Answered by J Glanz in a Response.

15a. K Wright, Very dark energy. Discover 22: 70-76, March 2001. Readable lay article 17. LM Krauss and GD Starkman, The fate of life in the universe. Scientific American 281: 58-67, Nov. 1999. Speculation of fate of the universe based on continued expansion.about new discoveries in cosmology, including increasing rate of expansion.

[iNow]

Just a note... All of those references are a decade old (or just under). It might be good to get something more current.