All Questions
Tagged with gravity reference-frames
103
questions
87
votes
6
answers
9k
views
If gravity is a pseudoforce in general relativity, then why is a graviton necessary?
As far as I’m aware, gravity in general relativity arises from the curvature of spacetime and is equivalent to an accelerated reference frame. Objects accelerating in a gravitational field are in fact ...
- 2,123
32
votes
4
answers
22k
views
Does gravity slow the speed that light travels?
Does gravity slow the speed that light travels? Can we actual measure the time it takes light from the sun to reach us? Is that light delayed as it climbs out of the sun's gravity well?
- 1,011
25
votes
4
answers
7k
views
If gravity is not a force, then how come gravitational assists work?
I have learned about general relativity and how gravity arises from spacetime curvature. And I have always been taught that gravity is not a real force in the sense that
$$\frac{dp}{dt} = 0$$
And from ...
- 1,896
20
votes
14
answers
6k
views
Why don't you feel gravity the same way you feel a car's acceleration? [closed]
If you are in an accelerating car or spaceship you feel an apparent force pushing you backwards, which as I understand is due to your own body's inertia (it wants to keep its current velocity but the ...
- 317
13
votes
6
answers
2k
views
Is spacetime curved in a near-earth-free-falling-object's frame of reference?
If I float motionless in outer space, I will measure spacetime to be approximately flat.
By the equivalence principle, I will get flat spacetime if I am free falling near earth.
Is this right? ...
- 131
10
votes
9
answers
4k
views
Why and when can the Earth be considered an inertial reference frame?
The question has been asked (e.g., here and here), but I would like to get a more definitive and mathematically formal answer.
The Earth rotates around its axis, around the Sun, and participates in ...
- 60.4k
9
votes
3
answers
1k
views
Can we determine an absolute frame of reference taking into account general relativity?
Given that acceleration induces measurable physical effects, would it be correct to say that there should be an absolute inertial frame of reference? I know that one cannot distinguish a priori ...
- 127
8
votes
5
answers
1k
views
Do you always experience the gravitational influence of other mass as you see them in your frame?
You see a galaxy far away. That galaxy is attracting you with a certain amount of gravity. I'm wondering if the gravity influence of the galaxy on you, as measured by you, always ends up being what ...
- 171
8
votes
2
answers
569
views
Mach's principle and a reference frame for acceleration
Although there are different statements of Mach's principle, one statement could be that acceleration is meaningless unless it can be defined relative to something. The distance stars provide a fixed ...
- 13.7k
5
votes
2
answers
5k
views
When objects fall along geodesic paths of curved space-time, why is there no force acting on them?
On cseligman.com, it is written that
So, we see things falling with an acceleration which we call the acceleration of gravity,and thinking that we live in a straight line , uniformly moving or ...
user36790
5
votes
1
answer
365
views
Explanation for "if all accelerated systems are equivalent, then Euclidean geometry cannot hold in all of them"
I'm doing an EPQ (mini college research paper) on gravity, and I found a site that explained things in simple terms. I am having trouble understanding how Einstein came to his revelation space-time ...
5
votes
2
answers
214
views
Comoving system of expanding or collapsing dust-like particles
I have a question on co-moving and synchronized reference systems. I read the corresponding section (97) in Landau/Lifshitz's second book "Field Theory" on it.
In particular it is said that space ...
- 9,778
5
votes
1
answer
3k
views
How to explain centripetal force in terms or relativity
At the end of a video of dropping a ball and feathers in a vacuum, Brian Cox explains that the Ball and Feathers, as understood in terms of General Relativity, aren't falling. (apologies I can only ...
- 153
5
votes
1
answer
3k
views
Curvature of spacetime in only required to explain tidal forces?
I'm a bit confused about the equivalence principle in GR.
I'm quoting from Wikipedia:
An observer in an accelerated reference frame must introduce what
physicists call fictitious forces to ...
- 1,075
4
votes
1
answer
3k
views
Relativity - Am I accelerating while standing on earth?
So I understand how a free-falling object in a gravitational field is "at rest" or has an inertial reference frame, but I cannot figure out why an object hovering in a gravitational field is supposed ...
- 239