Wherever there is matter in an ever-thinning universe, there might be an entire cosmologically-sized era dominated by an entirely different chemistry to what we have now.
Wherever there is matter in an ever-thinning universe, there might be an entire cosmologically-sized era dominated by an entirely different chemistry to what we have now.
Even with the universe expanding on a cosmological scale, I have a hard time seeing how or why that expansion should overcome the electromagnetic force locally, or the strong force for that matter.
Planets, solar systems,and galaxies are held together by gravity today, despite the space between galaxies expanding. The expansion of the universe doesn’t appear to be tearing things apart locally, why should it in the future?
To be clear: This is an honest question, I’m not an astrophysicist. My impression was that the expansion of the universe has no locally measurable effect, due to the forces holding things together being much stronger on a local scale than “whatever” is driving the space between things to expand.
Yes that’s my understanding as well. Although expansion is accelerating, so maybe some time very far in the future, expansion will in fact happen faster than the forces can compensate, and the universe will just be a very, very thin cloud of subatomic particles that can’t find another to form an atom with.
I may be off the deep end here, but I seem to remember reading that the acceleration can be explained by the fact that more space is created due to the expansion.
As an example: If space is expanding at 0.1 s-1, and we have 1 m3 of space, then the initial expansion rate is 0.1 m3s-1, after 1 s we have 1.1 m3 of space, which is expanding at 0.11 m3s-1, etc.
To reiterate: This is something I seem to remember reading some time, I’m not sure. However, if it’s correct, it would mean that the acceleration is happening between bits of matter that are moving apart, not within bits of matter that are already held together. In that case, the acceleration will never be able to pull apart matter. Please correct if I’ve gotten this wrong, as mentioned I’m not an astrophysicist.
Huh, that makes sense. (Though per H. L. Mencken, “For every complex problem there is an answer that is clear, simple, and wrong.”)
But space is between the nucleus and electrons too. There’s no difference between the space between atoms and the space between subatomic particles.
Absolutely, there is space between the electrons and nucleus (insomuch as the position of both is well defined). However, what I’m suggesting is that as long as there is an electromagnetic force holding the two together, such that there is a constant (time-averaged) distance between them, that space is not expanding at an accelerating rate. At least that’s my understanding of it.
Why would space there not be expanding like space everywhere else?
It is, but if the rate of expansion is constant (e.g. 0.1 m m-1s-1), then the acceleration in the speed of expansion that we observe is a result of the distance increasing.
So the space between two things that are 1 m apart will be expanding at 0.1 m s-1, while the space between two things that are 5 m apart will be expanding at 0.5 m s-1. As long as the force acting between two things is large enough to overcome the expansion rate right now, the distance between them will remain constant, because the acceleration is not a local effect but a result of the distance increasing.
As far as I understand, this is why we see other galaxies accelerating away from us, but don’t see any individual galaxy “ballooning”. Because locally (on the scale of a galaxy), gravitational forces overcome the rate of expansion. On large scales (to distant galaxies), there is effectively no gravitational pull, so the distance increases due to the expansion. When the distance increases, so does the observed speed of expansion, etc.
To reiterate: I’m in no way sure about this, it’s just my coarse understanding of our current explanation for what we observe.
No, all space is expanding. The space up in space just happens to look like it’s expanding faster because there’s more of it.
Nothing “overcomes” expansion. Not even the speed of light. There is a hard limit on how far telescopes can see into the cosmos because after a certain distance, the light emitted by stars will never reach the earth. This happens because the space between that star and our telescopes is expanding faster than the speed of light.
Now when you go to the other extreme, like subatomic particles, the same thing is happening, just much more slowly. You’ll need something like ten billion trillion years to actually see any hard effects from that expansion, but it’s still there. After long enough, even the space between atoms will expand faster than the speed of light. Fun fact: gravity also works at the speed of light. That’s the heat death of the universe.
Yeah. But the rate of expansion in general, at all scales, is indeed increasing.
The rate of expansion is determined by the Hubble constant, no? If I’m not completely mistaken, it’s commonly believed that the Hubble constant is slowly decreasing with time?
Expansion effects space, and since everything exists in space, expansion effects everything. The problem i think you’re running into is a mistake of scale. The expansion were talking about is TINY. As good as humanity can find to fit the definition of “infintesimal”. However, the universe is very, very big, and all that space adds up to compounding expansion the space in between.
In fact, once you get far enough away, all that expansion adds up to more than the speed of light. That’s why we can only ever see so far into the universe, and why that limit is always growing smaller. The light emitted from stars far enough away from us will never actually make it to earth because the space in-between that star and us is expanding, right now, faster than the light can travel.
Now take all this infinitely expanding space and multiply it by a bazillion years and eventually you will expand subatomic particles so far from each other that the strong and weak nuclear forces no longer interact. Space beats energy thanks to inverse square law, so eventually space wins the universe. Everything freezes and goes dark. That’s how the universe ends.
I think my point/question is a bit more subtle than a mistake of scale. It’s related to Hubbles law and whether the Hubble constant is increasing over time, and if it is, whether it has an upper bound.
I’m essentially suggesting that if the Hubble constant is either decreasing or has an upper bound that is not too high, two objects that are close together and held together by sufficiently strong forces will never be “torn apart” by the expansion of the space between them. This is because the space between the objects is expanding at a rate proportional to the distance between them, as given by the Hubble constant. If the forces between the objects are sufficiently large, they will be pulled together through the expanding space faster than the space is created.
Objects accelerate away from each other, even if the Hubble constant is decreasing (I don’t know if it is) because as the distance between them grows, there is more space between them expanding. Thus, two objects that are held together by some force will not accelerate away from each other if that force is large enough to pull them together faster than the space between them expands.
This is my current understanding of how space expands, please let me know if there’s something fundamental I’ve misunderstood :)
You’re going to want to read about the heat death of the universe. Basically if the cosmological constant is positive we’re going to end up in a cold dead universe a googolplex or more years from now. We don’t see the expansion locally or within galaxies yet because the universe is still young.
Isn’t the heat death of the universe essentially just the statement that because of the second law of thermodynamics all energy will eventually end up as heat? In other words: Entropy always wins in the end.
That is a bit different from stating that everything will be torn infinitely far apart, isn’t it?
Direct from the wiki on the heat death of the universe:
I think to get to the heart of what you are saying, don’t forget particles decay! So local accumulations have no choice but to evaporate basically over time