How will the universe end ?

Abidal Sala

If we proposed that the universe is expanding forever, will black holes eventually get rid of all ordinary matter? and what remains of the universe is just dark matter and dark energy ?

Cantstandit

If there is a black hole in the center of a galaxy, then it will probably suck the galaxy into it eventually, but I don't know if every galaxy has to have black hole in its center, or if it's not possible for a body to have stable orbit around such black hole.

Dark matter and dark energy are not necessarily actual matter and energy. These are just placeholder names for phenomena that we don't yet understand that look *like* it were matter and energy at work, that we can't see. It could turn out that it's not an additional matter, but that our equations were wrong, or that we were looking in wrong place/wrong way.

Ryan_m_b

There are multiple ideas as to the ultimate fate of the universe such as the heat death.Considering the time scales involved are on the order of 10¹⁰⁰ years (ten thousand, trillion, trillion trillion, trillion, trillion, trillion, trillion, trillion times greater than the current age of the universe) I doubt anyone will be around to see it.

salvestrom

Sean M Carroll stated (in a talk on cosmology) that all matter would end up in blackholes. I had previously ventured this opinion on these boards and was told 'no, that won't happen'. I currently have no idea who's right. This seems like a good thread to hammer it out.

Ryan_m_b

Why would you think it would? Note that black holes do not "suck". The gravity of a black hole is no different to the gravity of anything else, if the sun suddenly became a black hole it would make absolutely no difference to Earth's orbit (though it would get quite cold). To say that all matter will end up in black holes is to imply that over deep time all matter will at some point come into contact with a black hole. Without clear maths showing the probability of that it is an unfounded assertion especially considering the vanishingly small volume of the universe occupied by black holes.

See this section of the link I provided above.

salvestrom

Why I would think so isn't relevant. I was already shot down. The actual question is why did Sean M Carroll say it would.

EDiT: I actually read that link. It says 1-10% of a galaxy's content will end up in the blackhole. The rest will be flung out into empty space and decay into photons.

Haelfix

There is a blackhole era, where most matter in galaxies will be concentrated (the rest will have decayed into photons and/or be ejected)

See

http://en.wikipedia.org/wiki/Future_...nding_universe

But eventually they too will decay away via Hawking radiation.

What happens after that point is a real puzzle. The approximations used in statistical mechanics start to break down when you deal with length and timescales of that magnitude, and all sorts of exotic effects start to become possible!

Drakkith

Wouldn't orbital energy be radiated away over huge timescales by gravity waves?

Haelfix

There are several effects at play. Stellar winds, accretion rate's of matter etc. But over long timescales black holes mostly grow until the CMB cools sufficiently at which point Hawking radiation will dominate.

ynot1

As I see it electrical charges are stripped out of their atoms and ejected from black holes as high energy cosmic rays. The ultimate fate of the universe is charged particles and radiation. I suspect gravitational fields separate oppositely charged particles until the electrostatic forces overcome gravitational forces. Charged particles come together and annihilate, causing the quark-gluon plasma to be formed and another big bang.

Chronos

While most mass may eventually reside in black holes, it is unlikely all of it has this destiny. Even an extraordinarily thin gruel of matter dispersed throughout space creates havoc with most bounce models - unless you are willing to settle for gazillion of years between bounces.

Drakkith

I'm sorry, none of this makes any sense.

phinds

"As I see it" and "I suspect" are not helpful arguments and your statements are utter nonsense. Read some physics.

ynot1

I'm not a lawyer. I'm not here to litigate. I'm here to propose what I view as a most plausible scenario. You might try reading up on Van de Graf generators. Imagine an outer shell of positrons and an inner shell of electrons. Do you understand electrostatic attraction between unlike charges? What would happen in that case?

ynot1

The Van de Graff generator is used as an analogy of the universe after the black holes have long gone. Sorry for the confusion.

Certainly charge has no affect on gravitational attraction. Only matter. Charged particles do have mass, I believe. And gravity has effect on mass. I'm suggesting gravity has an attractive force on matter and a repulsive force on antimatter. Positrons, being I believe antimatter, would then be repelled by gravity. Electrons, of course, attracted. So as long as gravity is around it will separate positrons and electrons. I know it's is a bit indirect. Difficult to understand I guess. But I wouldn't waste time looking for any references about charge having any effect on gravitational attraction. Could be though. I just never thought about it I guess.

ynot1

I understand even the proton decays, but before that time it would most likely be recycled by a black hole.

Drakkith

The current view of science is that both matter and antimatter follow the same laws regarding gravity. It is "possible" that antimatter would be repelled, but by possible I mean that we simply haven't tested it conclusively yet.