

Double Logarithmic Timeline of the Universe - bungula
http://en.wikipedia.org/wiki/Graphical_timeline_from_Big_Bang_to_Heat_Death

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russell
I am not an astrophysicist or even a physicist, so bear with me. What happens
in the far future really depends on what theory you look at. Is dark energy
accelerating the expansion of the universe? If so, there will be a point where
all we can see is our own galaxy. Proton decay? Experimental evidence says
that protons are stable, or the half-life is much longer than 10^38 years.

Shock waves from supernovae trigger star formation by compressing the
intragalactic hydrogen, but they dont provide the material for fusion. (Lots
of other effects though.) So when the hydrogen is too dilute, star formation
stops. There are old galaxies wher star formation has essentially stopped.

Edit: I meant this as a reply to gpmedia, but pushed the wrong link, giving a
real astrophysicist the chance to reply.

~~~
andrewcooke
good point on burning all the hydrogen. i hadn't thought of that.

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gpmedia
Some of the information is this article is new for me. I know it's i
wikipedia, but the following facts in the Degenerate Era:

* Formation or new stars ceases. Stars cease to fuse.

* Solar systems no longer exists. Planets flung out of orbit or consumed by larger bodies.

* Galaxies no longer exist. Stars flung out of orbit or consumed bty black holes.

Have they been established as real facts? As far as I know dying stars go
Supernova and allow new stars to be born, thus repeating the full cycle.

~~~
andrewcooke
not all stars end in supernovae, and even supernovae may leave a core. see
<http://en.wikipedia.org/wiki/Stellar_evolution>

that means that matter is gradually "trapped" in brown dwarves, neutron stars
and black holes. so recycling by supernovae isn't sufficient to avoid heat
death (if only half of all stars give supernovae then in in just seven
"lifetimes" you've lost 99% of matter to those "sinks")

(maybe it's not clear, but that diagram is focusing on a _very_ long time
period, _much_ longer than the lifetime of any star that would go supernova).

but what happens in the very long term is, i think, something of an open
question (i am not an expert - i used to be an astronomer, but i've never
really thought about this before).

that diagram is based on work in a book that assumes two things: (1) that
protons decay and (2) the universe continues to expand. i haven't read the
book, but the conclusions seem reasonable given that assumption (afaik the
current consensus is that (2) is correct).

but they are just assumptions - see
<http://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe> for alternative
possibilities.

