What will happen to all matter in the end?

[Erasmus00]

Originally Posted by infamous

That would be true if we only defined stars as bright shining objects. .

I was just pointing out that all the stars would eventually burn out. I think, given enough time, matter would just sorta settle into a ground state. You'd have lots of cold lumps of iron floating around. White dwarfs, neutron stars and brown dwarfs still cool with time, and will continue to cool untill they hit a ground state.
-Will

[niviene]

Originally Posted by Erasmus00

The big bang, under standard model.
-Will

And nothing else in the universe expels hydrogen? (sorry, I really don't know this stuff...I hope I'm not coming across as being rude. )

[Erasmus00]

Originally Posted by niviene

And nothing else in the universe expels hydrogen? (sorry, I really don't know this stuff...I hope I'm not coming across as being rude. )

As far as I know, that is correct. All the matter in the universe started as hydrogen. Stars forge it into heavier elements, slowly over time. As far as I know, there is no source for fresh hydrogen.
-Will

[niviene]

Wow... I really had no idea. This is one field (of many) that I find fascinating but never learned more than the basics.

*begins running around with signs that read "The End is Nigh!"*

[EWright]

OK, I'm starting to question the competence of some of the knowledge on this site. The fate of all matter in the universe depends on the shape of the universe. The shape of the universe is what will determine ITS overall fate. Current projections are that because the universe is expanding at an ever-increasing rate, due to a force dubbed "dark energy", that it will continue to expand to the point that every atom in the universe will be spread into smaller and smaller particles. First galaxies will be spread so far apart that we would not be able to view other galaxies. Then our own start will become so distant that there'd be no other stars in the night sky (yes, i realize this is long after the earth is dead and gone). Everything will be spread so far and at such an increasing rate that gasses will not be able to form new stars, etc. See Scientific American magazin online for more info on this. It would have been about a year ago.

[CraigD]

Originally Posted by niviene

And nothing else in the universe expels hydrogen?

Originally Posted by Erasmus00

As far as I know, that is correct. All the matter in the universe started as hydrogen. Stars forge it into heavier elements, slowly over time. As far as I know, there is no source for fresh hydrogen

It is possible to produce hydrogen from heavier elements. Just knock the nuclei of heavy atoms together hard enough to break them into protons and neutrons, throw them back together with their electrons, cool them down, and you’ve got hydrogen and neutrons. Free neutrons decay pretty quickly – half of them every 10 minutes – into pairs of protons and electrons, which make hydrogen.

This can be done with a fairly old, low-powered particle accelerator. It’s reasonable to believe that some exotic astronomical objects like neutron stars may establish conditions where this can occur. So, while possible, it doesn’t happen in anywhere near the quantities that stars fuse hydrogen into helium, etc.

An important point is that making hydrogen from heavier elements takes energy, the major source of which is the fusion in stars of hydrogen, helium, and other elements up to but not including any as heavy or heavier than iron. So, once all the stars have fused hydrogen into heavier elements, there’ll be no energy left to transmute them back into hydrogen. Exotic objects – many-galaxy-mass black holes and the like – may postpone the energy shortage for a while, but not forever.

According to the currently Standard Model, either the universe will settle down to a lot of ordinary heavy elements, or be dominated by lots of super-massive neutron stars. (The Standard Model really doesn’t say much about anything more massive than big neutron stars – black holes – though mainstream cosmology is pretty convinced such super-massive black holes exists) Though it’s not a well-described, accepted part of it yet, many people think that the Standard Model will eventually allow for protons, free or in heavy nuclei, to decay into various kinds of weird force and matter. Experiments suggest that, if this actually happens, it’s happens super-slowly – half of all protons in 10^33 years. If this turns out to be the case, the universe will ultimately be a soup of weird particles, and either electrons, photons, or a mixture, with increasingly few atoms of ordinary matter, but only very, very far in the future.

All this Particle Physics stuff assumes that, on a large scale, the universe will keep expanding. If that turns out not to be the case – a real possibility, given the current poor understanding of such things – the deep future could be entirely different.