If the available energy is dispersed and chaotic, we won't be able to concentrate enough to perform the experiments? Though I doubt that'll be the case at any time while the human race is in existence...
If humanity lives to a point where entropy becomes a problem, I'm pretty sure our lives would be the first to go, not our "ability to perform experiments".
that entirely depends on the magnitude of the experiment.
If we were approaching any "universal energy" limitations, it'd stand to reason that our technology would be very much different than our technology now -- perhaps universe sized experiments would be feasible by that point, at which time we may hit a limit imposed on us not by anything other than the length of time since the last universe formation event, and our poor luck in meeting that point in technology at a time where the energy no longer exists to fuel it.
Unlikely, and I think your idea of life being threatened before science is probably much more rational, but it's fun to think about. Plus, if we were using that much energy for a single experiment, one would wonder about that experiments' safety.
You should first worry about how we get out of this planet before the Sun turns into a red giant and swallows the Earth after 5–6 billion years from now.
Please have some perspective. Human beings have existed in roughly our present form for 200,000 years. In another 200,000 years, chances are we won't recognize ourselves. And in 5 billion years, which is 25,000 times farther into the future, there will be nothing remotely resembling human beings. We won't be a distant memory, we won't be a memory at all.
I had a scheme, once, for everyone to be remembered. It started with one nearly impossible scheme, producing a biography for every person ever (starting with the living, with some effort made to recover as many of the deceased as are still remembered today). The problem with that is that being recorded is not the same as being remembered. Being remembered means that someone living knows about you and thinks about you. They occasionally ask themselves what you would think or do.
So you would need a system for everyone's life to be read from the recordings periodically, by at least one person. For the near future -- say a few thousand years -- this could work. For the first few generations, each living person could remember a small handful of the deceased, and all of the deceased would be held in living memory. Once the number of people to be remembered grew too great for that, you could still cycle them in from time to time. Being remembered by one person every thousand years could still be pretty nice.
But five billion years, that dog don't hunt. At current generation lengths, there'd be 200 million generations to be remembered. Unless you are willing to postulate either constant, exponential population growth, dramatic lengthening of generations, or superhuman capacity to remember, you couldn't remember any one person more than once every several million years. It still beats being forgotten, if that's your fear, but not by much.
That was my point. Natsu was worrying about the ability of a technological civilization to function near the heat death of the universe. Which is much further than 5-6 billion years away. A more "immediate" problem is the death of our own Sun.
> Natsu was worrying about the ability of a technological civilization to function near the heat death of the universe.
Unless by "heat death" he meant a cold death, current thinking has it that the universe will gradually cool off, and ultimately freeze, because of the endless expansion provided by Dark Energy.
The fact that the universe is expanding exponentially, i.e. with a positive second derivative, was the first shock. The second came when the implications of this observation began to sink in.
"Heat death does not imply any particular absolute temperature; it only requires that temperature differences or other processes may no longer be exploited to perform work."
(caveat: I know very little of real physics)