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The Big Crunch


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Thats the theory, evidently even black holes will radiate energy, and the universe will end up a very uniform, fairly cold, particle-less place.

So make sure you cash in your ISA's and 407K's in plenty of time, as you wont be able to spend 'em then!!!

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I believe wiseman has the current accepted theory, yeah. The most basic law of thermodynamics is that entropy increases.

In other words, any organised system will have a tendency to become less organised as time passes.

Taking our solar system as an example, orbits will gradually become more eccentric, natural satellites will slip free of their planets and the ain's behaviour will become more erratic.

At the moment, the universe isn't just expanding, that rate of expansion is actually accelerating.

In any explosion, there is a period of time when the constituent parts of the explosion are accelerated away from the centre of the explosion. Generally, that period of expansion is over in milliseconds, then the rest of the action is pretty much inertia and air currents.

If you think about that fact and equate it to the theory of the big bang, then 13.7 years ago, something ignited that explosion and the universe is still in the first few "milliseconds" of its existence.

In trillions of years, tens of trillions of years, the constituent parts of the big bang will have expanded to the point when thermodynamic temperature exchange can't take place and gradually, temperature will be lost to vacuum.

It is believed that when matter reaches absolute zero, the cohesive properties inherent to it are no longer functioning.

When that happens, atoms drift apart and maximum entropy is achieved. Time and space no longer have any relevancy. Atoms fall to their components, then those components fall apart as well.

I have a personal theory that this state of maximum entropy is the beginning as well as the end. Two or three particles meet by chance, energy is exchanged, another chance encounter, we see clumps of matter, gravity begins to take effect, the cycle begins again.

There is a lot of holes in the theory, but hey, I'm not a physicist, I'm just this guy, you know?

Alan

Excuse the typos, I'm typing on my phone.

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It's awesome to think about this kind of stuff. :D

What is existence? Is the universe always going to have a big bang and big crunch forever? If so, then nothing is permanent. But if the universe keeps expanding forever than eventually everything will die out.

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There is also theory of the big rip caused by accelerating expansion of space, which is fueled in theory by dark energy, as an energy of an empty space. According to this theory mather will by annihilated (riped) by expansion forces which will overcome gravity force.

See interesting lecture by Brian Schmidt who was member of one of the two teams responsible for discovery that expansion of the universe is accelerating.

Edited by spider72
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...the universe will end up a ... particle-less place.

So this model assumes proton decay? I asked Prof Cox this on twitter, which he kindly replied to, but 140 characters isn't really enough to answer the question properly. His answer was yes, but they don't know for sure yet. Can anyone else expand on this for me?

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Dark Energy looks increasingly likely to end the universe in the big rip, with everything ripped apart and a almost featureless universe.

However the ekpyrotic model of the universe, which I find quite attractive, requires this to happen as a prelude to a new big bang when two branes collide and restart the whole process - something that may have happened many times before!

As a side fact, it also helps explain inflation and a number of other early universe things, and is testable through high resolution cosmic microwave background data. So watch this... um universe!

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Effectively, yes it will happen from what we know. The universe will become more balanced again, due to "settling" of its contents, the rule of raising/higher entropy. The same mechanism also drove the expansion in the first place, when it was disturbed, imbalances occurred meaning matter could exist, for a while anyway...

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As i see it, the problem with the 'law of entropy' lies right in front of our faces. Or, to be more to the point, behind them. Us. Intelligent life. We're that massive exception to the rule, we create order out of chaos.

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Dark Energy looks increasingly likely to end the universe in the big rip, with everything ripped apart and a almost featureless universe.

I'm not sure about this, but maybe we mean different things by "big rip". In a Big Rip universe, the scale factor becomes unbounded at some finite time in the future. If dark energy is vacuum energy, this doesn't happen, i.e., the scale factor become (exponentially) unbounded at infinite time.

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As i see it, the problem with the 'law of entropy' lies right in front of our faces. Or, to be more to the point, behind them. Us. Intelligent life. We're that massive exception to the rule, we create order out of chaos.

Not really, we create lots of extra entropy to make that order. Far more than is consumed by making us. Its easy to reduce entropy locally, but doing it without generating excess entropy - usually in the form of heat or similar is the trick!

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I'm not sure about this, but maybe we mean different things by "big rip". In a Big Rip universe, the scale factor becomes unbounded at some finite time in the future. If dark energy is vacuum energy, this doesn't happen, i.e., the scale factor become (exponentially) unbounded at infinite time.

Well I think that is not much different if you happen to find yourself in such a place. Whether the universe is almost infinitely spread about, or infinitely spread about, its pretty featureless either way! :eek:

I don't think anyone knows what dark energy is (vacuum energy or otherwise), just what it's effects are at present.

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Not really, we create lots of extra entropy to make that order. Far more than is consumed by making us. Its easy to reduce entropy locally, but doing it without generating excess entropy - usually in the form of heat or similar is the trick!

I would say there's a difference between entropy and efficiency.

Even so - there seem to be two main theories, one of the Big Freeze, the other of the Big Crunch. Would it not be possible (albeit unimaginably unlikely) for the universe to reach equilibrium?

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I would say there's a difference between entropy and efficiency.

Even so - there seem to be two main theories, one of the Big Freeze, the other of the Big Crunch. Would it not be possible (albeit unimaginably unlikely) for the universe to reach equilibrium?

Equilibrium with what?

If you think of it as a hot gas in a thermos flask, then that would come to equilibrium at whatever temperature it was at. I.e., it would all be the same temperature with no hot spots.

However assume the thermos flask is continually getting bigger. The gas will cool down, as the space gets larger and larger the gas gets cooler and cooler. When the thermos flask is the size of the earth it will be very cold, make it the size of the solar system colder still, etc etc.

Currently it looks like dark energy (whatever it turns out to be) is accelerating the expansion of the universe, so everything will thin out. That's the force that is expanding the thermos flask.

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Equilibrium with what?

If you think of it as a hot gas in a thermos flask, then that would come to equilibrium at whatever temperature it was at. I.e., it would all be the same temperature with no hot spots.

However assume the thermos flask is continually getting bigger. The gas will cool down, as the space gets larger and larger the gas gets cooler and cooler. When the thermos flask is the size of the earth it will be very cold, make it the size of the solar system colder still, etc etc.

Currently it looks like dark energy (whatever it turns out to be) is accelerating the expansion of the universe, so everything will thin out. That's the force that is expanding the thermos flask.

Well if the theory of the big freeze is linked with dark energy, and the theory of the big crunch is linked with dark matter then between both of them?

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Well if the theory of the big freeze is linked with dark energy, and the theory of the big crunch is linked with dark matter then between both of them?

Dark energy wins! Dark matter had its day, it formed galaxies and galaxy clusters. It's holding on to what it can, but dark energy will win in the long run, it's winning now!

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Dark energy wins! Dark matter had its day, it formed galaxies and galaxy clusters. It's holding on to what it can, but dark energy will win in the long run, it's winning now!

Well surely we can't say that for sure since we can't technically prove the existence of either? Besides, it's not a competition - i'm talking about a hypothetical situation where the amount of dark matter in the universe is perfectly balanced with the amount of dark energy at a point where it is neither expanding or contracting.

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Well surely we can't say that for sure since we can't technically prove the existence of either? Besides, it's not a competition - i'm talking about a hypothetical situation where the amount of dark matter in the universe is perfectly balanced with the amount of dark energy at a point where it is neither expanding or contracting.

Well I guess it depends what you mean by prove. We don't really know what either is, although there are some good ideas for DM, but none proven yet. However, we can see what the effect is, no matter what its really made up of. There are about 4 different lines of evidence that show DM doing it's stuff, making measurable changes on large scales.

We can clearly see the presence of DM, because of its gravitational effects. We can also see the effects of DE, by looking at galaxies further and further away. There are about 2 different lines of evidence to show DE doing its stuff.

When you look at the contribution from both, which has been found by various experiments to narrow down exactly how much of each is present, it comes down to about 3:1 DE:DM.

The other thing is that the amount of DM is fixed, generated by the big bang. DE probably continues to grow as the universe expands as its a function of space (probably - depends on the exact theoretical model - although I'm a bit out of my depth there!).

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