This is pretty general.

Could a sentient species make the "heat death" of the universe impossible? Heat death, as the ultimate ending state for the universe, is just a universal temperature, throughout the universe, right? Well, if a sentient species still existed, couldn't it arrange it so that they never run out of energy, assuming they've had the previous billions of years to advance to a state where they're pretty good at manipulating matter? Or could we even do it in our current state?

AS far as I know, entropy will get you in the end, therefore in a closed universe, which this one looks like just now, there is no escaping it. damn. oh well. "we're doomed I tell ye, dooomed"

hmm.. maybe it's not a closed universe. I wonder... black holes rip apart space-time.. so doesn't that blow the whole "closed universe" thing?

ummm (damn, i wish id read that book on cosmology now) I htink it depends on whether the black holes go through to the same universe, or a different one. Then theres the event horizon, a pretty good barrier methinks. And i think its called hawking radtiaiton? where black holes can evaporate? so, that just monkeys things up even further.
If they go through to say a different universe, and theres all these universes that form a torus shaped doughnut with multiple layers all expanding from a common point, perhaps we could just step down into younger universes all the time, and keep going that way, but then would they be the same in all these cosmological constants?

I think my brains starting to hurt.

Fafnir665:
I would think that you could fight off entropy for a while, but you're fucked in the end. Whether one could "tunnel" into another universe through an Einstien-Rosen bridge is another question.

Maximum entropy in a system can only happen at time infinity, would the "fucked in the end" be a point where the universe is at a maximum observable entropy. Would an einstien rosen bridge include a nakid black hole?

You have a lower and lower quality of living as there is less localized energy for you to use. All the stars will eventually burn out and then the intersteller hydrogen will be too thin and depleted to run a bussard ramjet. You could extract energy from black holes for a while but they eventually evaporate. At some point there just isnt enough energy to support any concievable form of life.

It might be trillions of years before this happens but in the end the universe is a deathtrap. I dont know if there is a way out but if we stay we die.

How well is the zero point energy theory accepted in mainstream
physics? Is it a "fringe" or crackpot theory? Is it dependent on
other physical components of the universe, such as stars, black
holes, etc. to exist and is zero point energy thought to be finite?
As you can see, I know very little of the theory and these are
honest questions, not intended to be argumentative, but maybe
a little thought provoking.

Of the universe or of a local ecosystem?

The book you seek is "Gravity's Rainbow."

To stave off the heat death there are several strategies- you start by surrounding every star you can with energy traps, saving the starlight in a big high tech battery (perhaps as antimatter) until all the stars run out;
you can even slow down the lifetime of the star by stripping mass off the star (smaller stars burn more slowly)

Once all the stars have died and you have used all the stored energy- this will be perhaps a couple of hundred billion years from now-
you can start living off the Hawking radiation emitted by black holes-
and to suppliment this you can gather all the mass of the dead stars and chuck them into artificial black holes- this converts dead matter into energy quite nicely...

eventually, a few trillion years or more later you will want to shut down into an energy saving mode, running sentient programs on processors that reverse the computations as far as possible, and use little energy.
Proton decay will detroy solid matter by 10^37 years, but if there is any way to exist without protons, there will still be a few galactic black holes around weakly radiating until 10^100 years- that is a googol years from now...
long enough?
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SF worldbuilding at
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At the time maximum entropy is acheived the system may not be very interesting, but that doesn't mean that time has to have reached infinity.

I think a sentient species could prevent a heat death from happening if it were advanced enough. Obviously, a species like that couldn't exist at the same time as a "heat death" by your definition of Heat Death because the species is part of the universe. That answers the energy question. They couldn't use the heat for energy because there's so much heat that they couldn't exist. Nothing can live in total entropy.

They couldn't use the heat for energy because there's so much heat that they couldn't exist. Nothing can live in total entropy.

You are right, nothing could live in total entropy, but because of the expansion of the universe the temperature at the time of the heat death will actually be very very cold.
There won't be enough energy around to gather material together into organised forms, and so entropy will be complete.
Negentropism
-------------------------------
SF worldbuilding at
http://www.orionsarm.com/main.html