do you believe in it? more importantly, if yes/no, what’s the reason why / why not?
i have had a great number of very enjoyable discussions with people about this topic. some say that it is unknowable what the eventual fate of the universe will be, because we can never have experimental confirmation that things will keep on moving forever, unless we wait for the end of the universe, which will never come (or at which point the knowledge would be useless).
however, i keep thinking that cosmic expansion will lift things out of a gravitational potential over time. i’m assuming that we’re all inside a big black hole (the whole universe is a black hole as an object with the mass of the entire observable universe just so happens to have a schwarzschild diameter of about the diameter of the entire observable universe). as the universe expands, its density decreases, therefore its schwarzschild radius decreases and we will eventually leave the black hole without doing anything for it; this obviously adds energy to the system.
or, in case cosmic expansion does not continue exponentially (but slows down over time), then the laws of physics would change over time; then, according to noether’s theorem, we could extract useful energy out of that change of laws over time. also black holes could grow to infinite size simply feeding on cosmic microwave background radiation continuously in this case¹. which we could use as an energy source.
[1]: do the differential equation, you get dM/dt ∝ M²·u₀/a(t) where M is the mass of the black hole, M² is proportional to the surface area, a(t) is the scale factor, and u₀ is the CMB density at current time. If a(t) is less than exponential, i.e. less than exp(Ht), then M(t) diverges in finite time for any black hole with big enough start mass.
sorry for such a verbose post :)
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The universe doesn’t care whether we believe in its heat death. It does get mildly annoyed at being anthropomorphized though.
The problem is, the closer we get to heat death, the closer we get to a state where universal forces won’t reliably line up like they do today, and there’s no way to properly simulate this state from within our current universe.
That is to say, even if we can perfectly model what MAY happen, when we get to the point where forces will all act on matter and energy at the quantum level with the same level of influence, we’d need to have fully and completely modeled the universe to figure out what happens next.
Personally, I’m of the opinion that it all happens next, and won’t be for the first time.
Ultimately, a lot of the ideas you’re talking about are just models. Models are useful insofar as they can explain data and make predictions. “Believing” in a model isn’t something that scientists do. We use models as long as they’re useful, update them with new information, and abandon them if they stop being useful.
One important thing about hypotheses and the models they feed into is that they are falsifiable. If there’s nothing that could prove an idea wrong, it’s not really science. String Theory is a good example of this. It’s totally internally consistent but it’s almost perfectly designed such that any measurement that could be made to prove it wrong is completely impossible. To me, that’s not science anymore, it’s some sort of mathematical philosophy.
The “universe is a black hole” idea fits into this not-quite-science frame. Any data that could prove it wrong would only be gathered from outside the observable universe, which is impossible. So, unfortunately, it’s not quite science.
I don’t think being falsifiable is the most important part of a model. It’s their ability to make accurate predictions about what happens in reality. All models are wrong. Some are useful, the saying goes.
Newtonian mechanics, which we know is wrong, can still be used accurately for a lot of near-earth orbital calculations. It got the Apollo missions to the moon.
It’s my understanding that one of the most useful things about string theory is that it can make some really complicated or intractable problems much easier to solve within its frameworks. That’s valuable, regardless of how truthful it is that everything is made of 11 dimensional strings.
The trouble with string theory is that plenty can be explained given its axioms and what comes out of the resulting math, but those axioms are completely unproven and unprovable and I haven’t seen anything come out of it that have turned into real world results.
I read some time ago a mathematical proof, or rather an article claiming so because I don’t know enough neither math nor cosmology, supporting my own old intuitive concept that once heat death is complete and all matter has stopped moving and there is an eternity ahead of still nothing, it is by all relevant means identical to a singularity of potential energy.
I don’t know if I believe in it, but I think it makes sense. Even if it takes an eternity or two for a new cycle to start over.
Edit: I mean all of it is speculation anyway. We have and will never have any insight in the “true” nature of the universe beyond our limited measurements and deductions. It could be just what it looks like and there is only one. There could be a finite or unlimited number of multiverse, or a numeral concept beyond what we can comprehend. This could all be an illusion, a simulation, or a super organism of which we are part of or we could be microbes on it. In the end it doesn’t even matter really. But it’s fun to think about.
Physics happens right in front of us all the time. If you think it’s wrong, you need to show how in order to be believed; a lot of people have measured it and gotten the traditional results.
however, i keep thinking that cosmic expansion will lift things out of a gravitational potential over time.
Heat death is about statistics, not gravity. A “typical” physical situation is a situation you can’t run a machine or a living organism on, basically. The universe started in a “weird” (low entropy) situation, but seems to be wandering back towards a typical (high entropy) one as things happen.
Black holes outlasting everything else is a different thing that might happen in the far future.
or, in case cosmic expansion does not continue exponentially (but slows down over time), then the laws of physics would change over time;
Not sure where you heard that. Cosmic expansion staying too small to really notice at normal scales, and physics running the same way as ever is a definite possibility.
BTW, in the future, you’ll get more nice, helpful replies if you frame it as “why doesn’t X alternate possibility happen?”. That’s usually a great question and an opportunity to learn, and it doesn’t disrespect anyone.
