All Questions
Tagged with speed-of-light space-expansion
77
questions
-4
votes
2
answers
102
views
Can we use the fabric of spacetime to go faster than the speed of light?
If the fabric of spacetime isn't bound by the limit of the speed of light (the universe is expanding faster than the speed of light), could humans somehow wrap a spaceship in a bubble of the fabric of ...
2
votes
2
answers
477
views
Why can't we see past the observable universe?
Why can't we see light from beyond the observable universe?
I've done a lot of research on this and all I've found is unsatisfactory answers and straight up nonsense.
Some claim that the universe &...
- 131
2
votes
2
answers
149
views
Cosmic expansion and the speed of light
The light from the galaxy GN-z11 took 13.4 billion years to arrive, but its distance from the earth is 32 billion lightyears. This is commonly explained as a result of cosmological expansion, i.e. ...
- 7,504
0
votes
1
answer
59
views
Visualizing the Hubble Sphere
I have viewed the definitions of the Hubble Sphere and related cosmological concepts, as well as various explanations, yet Im still struggling to comprehend a full visualisation of this, which I would ...
0
votes
1
answer
35
views
Do most distant objects on the Hubble diagram 'tell' as the Hubble constant has been valid for at least 60 million years?
As we all know the deeper we look into the space the further we look into the past... So if the Hubble diagram shows the most distant objects at a 20 Mpsec or ~60Mly distance from us (and as for not ...
- 2,255
0
votes
0
answers
25
views
Does only the space region movement due universe expansion affect the possibility of viewing a star?
My question is maybe simple and easy to answer because the intrinsic speed of the star affects only the final frequency of observed light but are there any tricks about the combination of object ...
- 467
2
votes
1
answer
82
views
In an expanding universe, can two people communicating to each other about their cosmological horizons get around their horizon limit?
I want to pose a preamble question that I will answer first to build up to the main scenario. Then I will pose the main question. The main question concerns the special case of an expanding universe ...
- 8,640
4
votes
3
answers
759
views
Constant speed of light violates accelerating expansion of universe?
My question regards the following:
One of the most fundamental principles of Einstein's GR is that all free bodies move through spacetime with constant velocity $c=1$.
However, in 1998 Hubble showed ...
- 201
1
vote
3
answers
136
views
Measuring the Hubble Constant
Attempts to measure the expansion of the universe have come in various forms. The recent Cosmology Crisis (https://www.space.com/why-is-there-a-cosmology-crisis) has me pondering the expansion rate ...
- 11
-3
votes
1
answer
91
views
What is the “conspiratorial anisotropy” if we would see no star redshifts in one direction of the sky? [closed]
Suppose we see no redshift of stars in one direction only (or better, in directions on a small patch around it). And suppose in that direction (on a patch of sky around it) we see a lot more stars ...
1
vote
2
answers
136
views
Is a photon emitted beyond the Earth cosmological event horizon towards Earth actually moving away from Earth?
Is a photon emitted beyond the Earth cosmological event horizon towards Earth actually moving away from Earth due to space expansion? Is that the reason why we can't see beyond the horizon?
- 2,255
3
votes
2
answers
130
views
Faster-than-light gravitational waves and faster-than-light expansion in the inflation
I have no introduction to the inflationary epoch. I know, however, that during this time space-time expanded with a speed faster than the speed of light. If gravitational waves are perturbations of ...
- 585
2
votes
1
answer
169
views
How can a photon emitted when the universe was just a few lightyears in diameter, travel for billions of years without bumping into something?
Admitted: I find it already surprising that a photon can travel for billions of years without bumping into something in a universe that has the size of current observable universe but there I guess ...
- 289
2
votes
2
answers
113
views
What would the size of the observable universe be if you traveled 3/4 the speed of light?
I have a conceptual mess in my head and would like to clean it up.
From the perspective of Earth, we can measure the observable universe diameter at current at 93BLY. I understand this and why/how ...
- 121
3
votes
3
answers
210
views
Why can't the speed of gravitational waves be greater than the speed of light if the universe can expand faster than the speed of light?
Since the expansion speed of the universe can be greater than the speed of light, why can't gravitational waves, which also uses space as the medium, travel faster than the speed of light?
- 123