2 ms·

It's only been a finite time since the universe was very small, so unless it's expanding infinitely fast, I don't see how it could be infinite

immibis 1y ago
Was the universe infinitely small or was it just extremely or infinitely dense? Anyway, we don't actually know that, since we do not have a time machine. The theory that the universe used to be much smaller is something we infer based on the snapshot we see today, just like we infer rotation based on the snapshot we see today. Either one could yet be proven wrong.
atkailash 1y ago
[dead]
ben_w 1y ago
It's (mathematically) allowed for it to have always been infinite, and still grow. If you take the number like and apply f(x) = 2x, it was infinite before and after.
- voidUpdate 1y ago
  yes but if x is finite, any f(x) will still be finite. So the universe has either always been finite, or always been infinite, and given that it started out being very small in a big bang, it would imply the former
  - lumost 1y ago
    not if x is the set of all Real numbers. All points could have been infinitely close to each other at the big bang, and the universe could still have been infinite in size.
  - ben_w 1y ago
    > yes but if x is finite, any f(x) will still be finite. The number line is not finite, even though every value on it is. The universe may be like the number line. > and given that it started out being very small in a big bang, it would imply the former The universe started out denser, which is not quite the same as "small" when talking about infinities. The currently visible universe gets both things at the same time, but only because the visible bit is finite. Apply f(x) = x * 1e-60 to the number line, and things which were previously spaced out every integer, are now much more densely packed, but the number line as a whole is still the same size — infinite.
  - AnimalMuppet 1y ago
    f(x) = tan(x) f(x) = 1/(1-x) So if x is finite, f(x) can still be infinite.
adgjlsfhk1 1y ago
we don't know that the universe was ever small, just that it used to be a lot denser than it is today.

immibis 1y ago

Was the universe infinitely small or was it just extremely or infinitely dense? Anyway, we don't actually know that, since we do not have a time machine. The theory that the universe used to be much smaller is something we infer based on the snapshot we see today, just like we infer rotation based on the snapshot we see today. Either one could yet be proven wrong.

atkailash 1y ago

[dead]

ben_w 1y ago

It's (mathematically) allowed for it to have always been infinite, and still grow. If you take the number like and apply f(x) = 2x, it was infinite before and after.

voidUpdate 1y ago
yes but if x is finite, any f(x) will still be finite. So the universe has either always been finite, or always been infinite, and given that it started out being very small in a big bang, it would imply the former
- lumost 1y ago
  not if x is the set of all Real numbers. All points could have been infinitely close to each other at the big bang, and the universe could still have been infinite in size.
- ben_w 1y ago
  > yes but if x is finite, any f(x) will still be finite. The number line is not finite, even though every value on it is. The universe may be like the number line. > and given that it started out being very small in a big bang, it would imply the former The universe started out denser, which is not quite the same as "small" when talking about infinities. The currently visible universe gets both things at the same time, but only because the visible bit is finite. Apply f(x) = x * 1e-60 to the number line, and things which were previously spaced out every integer, are now much more densely packed, but the number line as a whole is still the same size — infinite.
- AnimalMuppet 1y ago
  f(x) = tan(x) f(x) = 1/(1-x) So if x is finite, f(x) can still be infinite.

adgjlsfhk1 1y ago

we don't know that the universe was ever small, just that it used to be a lot denser than it is today.