5 ms·

Sure. You could model it as being there being an extremely weak expansion force happening between your fingers, but the force not being enough to overcome any o

Sure. You could model it as being there being an extremely weak expansion force happening between your fingers, but the force not being enough to overcome any other local forces (gravity, molecular bonds, etc)… said force is not strong enough to overcome planetary orbits either, or orbits of stars around the galactic center, or the orbits of nearby galaxies around each other… but once you start getting into intergalactic scales where the force attracting galaxies together is very weak, the expansion force starts to actually make a difference. But the point is the space between your fingers isn’t literally expanding. It’s not like the universe is just expanding everywhere uniformly, which is what tux3 seemed to imply. The distance between your fingers is staying the same, and so is everything else nearby.

layer8 3y ago
My point though is that yes space is literally expanding everywhere uniformly, it’s just expanding “through your fingers” (i.e. your fingers don’t expand along with it) because the local forces keep your fingers (and the planet and the galaxy) together. This is roughly similar to how planets don’t collapse due to gravity, because the stronger electromagnetic repulsion makes them stable bodies, but this doesn’t mean that the gravitational field still isn’t there throughout the planet.
- deleted 3y ago
  [deleted]
sudosysgen 3y ago
If you inflate a balloon, you're not stretching out the dust on its surface.
d_tr 3y ago
> It’s not like the universe is just expanding everywhere uniformly, ... I thought this is exactly what most modern physicists believe. The wavelength of photons travelling in space is supposed to scale perfectly with the expansion of the universe, like an ink dot on a balloon getting wider as the balloon is being inflated. This is why we have the Cosmic Microwave Background consisting of photons that would have been maybe in the UV range when emitted by excited atoms back when the universe became "transparent".
- ninkendo 3y ago
  This is hard to communicate so I’m sure I’ve been misleading. “Space” is expanding uniformly, yes. But not the matter that exists in space, nor is the distance between local matter increasing. It’s not like the entire universe is undergoing a magnification of scale where everything is enlarging including each individual atom. So it’s misleading to say “the space between your fingers is expanding”, because it might give the impression that the distance between your fingers will actually be larger as time passes. This is not the case. If “space is expanding”, but the matter inside this space is unaffected by said expansion, then you’re left with a very subtle phenomena which is easy to misunderstand.
  - d_tr 3y ago
    > This is hard to communicate ... True. I think that the best way to explain this to someone who does not know about the phenomenon is to start with the phrase "existing space continuously creates new space" and everything should follow from this fact.
  - antifa 3y ago
    I actually find your "it is and it isn't" to be much more confusing than "it is but the other forces recompact matter faster than the new space emerges".
  - saltcured 3y ago
    So then all our parts are "falling" together constantly through this expanding space? I say falling, but I understand it is other local forces besides gravity. I struggle to wrap my mind around what that means for concepts I learned long ago in college physics... what is an inertial frame of reference then? What about the speed of light and relativistic effects? I suppose the answer is back to the original statement that the effect is really only noticable at cosmological scales. Locally, it's well below any margin of error?

layer8 3y ago

My point though is that yes space is literally expanding everywhere uniformly, it’s just expanding “through your fingers” (i.e. your fingers don’t expand along with it) because the local forces keep your fingers (and the planet and the galaxy) together. This is roughly similar to how planets don’t collapse due to gravity, because the stronger electromagnetic repulsion makes them stable bodies, but this doesn’t mean that the gravitational field still isn’t there throughout the planet.

deleted 3y ago
[deleted]

sudosysgen 3y ago

If you inflate a balloon, you're not stretching out the dust on its surface.

d_tr 3y ago

> It’s not like the universe is just expanding everywhere uniformly, ... I thought this is exactly what most modern physicists believe. The wavelength of photons travelling in space is supposed to scale perfectly with the expansion of the universe, like an ink dot on a balloon getting wider as the balloon is being inflated. This is why we have the Cosmic Microwave Background consisting of photons that would have been maybe in the UV range when emitted by excited atoms back when the universe became "transparent".

ninkendo 3y ago
This is hard to communicate so I’m sure I’ve been misleading. “Space” is expanding uniformly, yes. But not the matter that exists in space, nor is the distance between local matter increasing. It’s not like the entire universe is undergoing a magnification of scale where everything is enlarging including each individual atom. So it’s misleading to say “the space between your fingers is expanding”, because it might give the impression that the distance between your fingers will actually be larger as time passes. This is not the case. If “space is expanding”, but the matter inside this space is unaffected by said expansion, then you’re left with a very subtle phenomena which is easy to misunderstand.
- d_tr 3y ago
  > This is hard to communicate ... True. I think that the best way to explain this to someone who does not know about the phenomenon is to start with the phrase "existing space continuously creates new space" and everything should follow from this fact.
- antifa 3y ago
  I actually find your "it is and it isn't" to be much more confusing than "it is but the other forces recompact matter faster than the new space emerges".
- saltcured 3y ago
  So then all our parts are "falling" together constantly through this expanding space? I say falling, but I understand it is other local forces besides gravity. I struggle to wrap my mind around what that means for concepts I learned long ago in college physics... what is an inertial frame of reference then? What about the speed of light and relativistic effects? I suppose the answer is back to the original statement that the effect is really only noticable at cosmological scales. Locally, it's well below any margin of error?