All Questions
10
questions
20
votes
5
answers
3k
views
Wouldn't the cosmic background radiation (CMB) produce drag and thus create a preferential inertial frame?
Because the CMB is everywhere and is isotropic, if an object would have a certain velocity, it could have a pressure differential produced by the CMB which would produce drag till it would stop with ...
- 2,035
0
votes
1
answer
98
views
Why don't galaxies have larger peculiar velocities?
I am trying to reconcile two facts:
That galaxies' comoving velocities are generally close to zero, and
That the universe has no preferred reference frame.
Galaxies seem to move very little relative ...
- 373
5
votes
3
answers
1k
views
What causes the Sagnac effect?
Wikipedia explains the Sagnac effect as a result of the rotating disk, which moves the target so that one of the light beams has farther to travel and consequently, will arrive later than the other ...
- 51
0
votes
1
answer
42
views
Inertial mass increase of the farthest receding galaxies
If the farthest galaxies that we can see are receding at near the speed of light, shouldn't this increase their inertial mass as well relative to our galaxy?
1
vote
3
answers
182
views
Relativity and the age of the Universe
I put my assistant in a spaceship and accelerate it to near the speed of light. 100 years from now (in my time), my assistant is travelling with speed $0.99c$. At that time I put up a super ...
user32023
2
votes
2
answers
241
views
What should I consider as an observer to measure the speed of cosmic objects?
I mean for example if earth is the observer, then there might be entire galaxies travelling faster than the speed of light relative to earth. So according to Einstein relativity this shouldn't be ...
- 23
0
votes
0
answers
33
views
Is the Hubble parameter different for each observer?
As the universe expands, galaxies disappear beyond the observable universe. So we could calculate the rate of expansion of the universe (the Hubble parameter) by estimating the rate of disappearance.
...
- 333
2
votes
2
answers
124
views
Is the age of the universe different for a returning space traveller?
When an astronaut returns to the planet he came from, he would then count the exact same number of galaxies as an observer on that planet, but they could have had experienced wildly different amounts ...
- 333
-1
votes
2
answers
988
views
Most stationary object in the universe
There is an object in the universe for which the Sun appears to be more stationary as it travels through the universe than a star on some other system. There is probably another object for which both ...
- 21
0
votes
0
answers
58
views
What does velocity relative to CMB mean? [duplicate]
I've see some velocities such as that of the Sun quoted as "relative to the cosmic microwave background"?
How is this different to measuring velocities relative to that old, discredited idea, the ...
- 5,148