why is it said that the objects on the other side of the big bang's light wont reach

[SMOGZINN]

I understand how space is stretching between long distances. But is this a constant phenomena? Does light stretch even on short distances like from a campfire's light to the observer's eyes? I am assuming that this stretching is undetectable to most sensors.

Ahh, I hate relativity-based principles! I read and read up on you and I forget all the information by the end of the week. Good old Newtonian physics, how I miss you.

IIRC this is something that is still being investigated, but it appears right now that the expanding of space mostly happens far away from matter in the huge mostly empty expanses of between the galactic clusters.

 

[Revolution 11]

But that makes no sense. Why would the expanding be non-uniform in distribution? I thought that a redshift is purely dependent on distance as the further the object, the more noticeable the shift. Or is it that the further the object, the faster the expansion?

 

[Sunny129]

I understand how space is stretching between long distances. But is this a constant phenomena? Does light stretch even on short distances like from a campfire's light to the observer's eyes? I am assuming that this stretching is undetectable to most sensors.

while many relativistic phenomena do occur over everyday (relatively small) distances and time spans just as they do over cosmological (relatively large) distances and time spans (such as time dilation, length contraction, etc.), cosmological redshift is not one of them. the camp fire example is in the realm of the gravitationally bound, and therefore the spacetime in the immediate vicinity of such a scenario does not stretch...which means light traversing that space does not get red-shifted.

I thought that a redshift is purely dependent on distance as the further the object, the more noticeable the shift. Or is it that the further the object, the faster the expansion?

both...the relationship is linear in either case. if the measured redshift is A at a distance of B, then the measured redshift at a distance of 2B is 2A. likewise, if objects at a distance of A are moving away from us at a velocity of B, then objects at a distance of 2A are moving away from us at a velocity of 2B.

 

[bwanaaa]

Not necessarily. Two objects can be locally stationary and yet have a redshift w.r.t. each other. No motion is necessary if space expands.

Indeed. I have also wondered about the effect of gravity on redshift. My inspiration is Einstein's illustration of the equivalence principle. In an elevator, you cannot tell if there is gravity and you are stationary OR if the elevator is accelerating upwards. So extending this analogy to the universe, we should have the same problem.
Is spacetime expanding or is it under the influence of a strong gravitic field?

Where would this gravity come from? dark matter. Especially since so much dark matter exists in the universe, the gravitic contribution to redshift should be significant. Since dark matter is not observable with EM, and there is SO MUCH of it in the vastness of space, it follows there is a strong gravitational field in space where we see nothing else. The effect of gravity on doppler shift is no different than the effect of an accelerating spacetime expansion. Well, maybe the magnitude of the effect is different but then that the depends on the acceleration of spacetime expansion.

Ever since vera rubin, there have been tantalizing paradoxes about galactic velocities. Is it possible when looking at these vast scales of distance that 'dark gravity' is affecting the speed of light. Yes, I said it. Dark Gravity. That would be the force generated by dark matter. Of course, the evidence for the existence of dark matter began with measurements of orbital velocities and the inferred gravitational forces. When these forces far exceeded the observed mass, we postulated dark matter. Certainly, alternative explanations like a non-constant gravity have been entertained although I am unclear on the data that refuted them. So, really, dark gravity, per se, does not exist, but rather I am referring to that component of gravity that derives from dark matter.

My point is that maybe spacetime is not expanding at an accelerating rate, maybe it just *appears* so, due to dark gravity.

 

[Sephire]

I saw an episode where Brian Cox discussed this subject.