# What keeps the universe going and will it stop or go on forever?

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I'm not sure if I mean matter or the entire universe in general since I lack the technical knowledge to really understand what I'm asking but I'm going to ask anyway.

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What do you mean by "keeps it going"?

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Not sure what the question is, maybe you wish to discuss the ultimate fate of the universe and what alternatives the current models for the universe may contain? For instance Big Rip* (Universe continues to expand) vs Big Crunch* (Expansion will halt and a contraction will follow) ?

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If by 'keep on going' you mean do things, like work, then it is energy that keeps it 'going'.

Energy has some funny properties.
If you have a box divided by a partition, where one side has a more energetic gas than the other side, the partition will be accelerated, and move. That is an example of doing work ( much like the pistons moving in your car's engine let you travel down the road )
When the gas on both sides of the partition has equal energy, obviously the partition will stop moving, and no more work can be done.
Notice that the total gas still has energy, but it is the difference in energy that allows work, and processes to happen.

So, we have useable energy, which can do work, and un-useable energy which cannot.
We call this process, of converting useable energy into un-useable, entropy.
Entropy can also be a measure of the 'order' of a system, which means that, although it can be reversed locally ( life is proof of that ), it must always increase globally. That is where the idea for the 'heat death' of the universe comes from. Once entropy of the universe is maximized, and there are no more energy differences, all work and processes will cease, and the universe will essentially be dead.

This is a rather simple explanation, which is, hopefully, suitable for your level of understanding.
If you should need elaboration, don't be afraid to ask.

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The discovery of an acceleration in the expansion rate, suggests that space will expand forever and ever, amen.

All the matter in the universe will though undergo decay at various rates...stars will go nova and supernova, WD's will become black cinders, BH's will evaporate via Hawking radiation, and possibly even protons will undergo decay. The universe/space/time, will be a cold dark place. We are though looking at a time frame approaching hundreds of trillions of years.

Edited by beecee
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4 hours ago, MigL said:

This is a rather simple explanation, which is, hopefully, suitable for your level of understanding.
If you should need elaboration, don't be afraid to ask.

Simple but really cool. +1

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On 9/14/2021 at 4:16 AM, studiot said:

Simple but really cool. +1

I can only second that +1

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• 4 weeks later...
On 9/13/2021 at 7:15 PM, MigL said:

If by 'keep on going' you mean do things, like work, then it is energy that keeps it 'going'.

Energy has some funny properties.
If you have a box divided by a partition, where one side has a more energetic gas than the other side, the partition will be accelerated, and move. That is an example of doing work ( much like the pistons moving in your car's engine let you travel down the road )
When the gas on both sides of the partition has equal energy, obviously the partition will stop moving, and no more work can be done.
Notice that the total gas still has energy, but it is the difference in energy that allows work, and processes to happen.

So, we have useable energy, which can do work, and un-useable energy which cannot.
We call this process, of converting useable energy into un-useable, entropy.
Entropy can also be a measure of the 'order' of a system, which means that, although it can be reversed locally ( life is proof of that ), it must always increase globally. That is where the idea for the 'heat death' of the universe comes from. Once entropy of the universe is maximized, and there are no more energy differences, all work and processes will cease, and the universe will essentially be dead.

This is a rather simple explanation, which is, hopefully, suitable for your level of understanding.
If you should need elaboration, don't be afraid to ask.

Yeah, I loved your lowdown too.

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On 9/13/2021 at 11:15 AM, MigL said:

This is a rather simple explanation, which is, hopefully, suitable for your level of understanding.

But M Kaku used flowerier language and a LOT more drama and made it sound so sensational in his books! Next time, maybe some explosions. And more cowbell.

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