All Questions
Tagged with relative-motion general-relativity
33
questions
118
votes
13
answers
42k
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If all motion is relative, how does light have a finite speed?
I've often heard that Einstein shattered the notion of absolute motion (i.e. all things move relative to one another) and that he established the speed of light as being absolute. That sounds ...
- 1,321
16
votes
10
answers
5k
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Why do bodies traveling at constant velocity experience the same physics?
I am new to special relativity. I don't have a background in physics.
I was reading Brian Green's The Elegant Universe and got hung up on an example.
In fact, Einstein realized that the principle of ...
- 279
11
votes
3
answers
7k
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How can you accelerate without moving?
I know this question has been asked in other forms, generally regarding the balance of forces. This time I want to focus on motion. I've got a laser accelerometer on my desk. It tells me that I'm ...
user32023
7
votes
6
answers
3k
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Does Special Relativity Imply Multiple Realities?
Thank you for reading. Before you answer my question, I feel I need to let you know that I'm still a beginner in special relativity...so the more thorough the answer, the better. Thank you! Alright, ...
- 3,075
7
votes
1
answer
419
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How to calculate relative velocity in curved spacetime?
Is there a nice geometric way to calculate relative velocity in curved space time? I'm looking from something similar to how the separation vector $n$ between $2$ neighboring geodesics obey:
$$ \...
- 1,389
7
votes
1
answer
2k
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What is my acceleration in my own frame?
This is , I suppose not a good question , but I think I am missing something which confuses me in this question.
So my question is:
Velocity is relative. So suppose a car is moving at a speed $200 \;\...
- 2,797
6
votes
5
answers
2k
views
Space Expansion vs. Relative Motion
Given 2 objects moving at some velocity $v$ relative to one another, is it possible to determine whether they are moving or whether the space between them is expanding?
- 2,627
5
votes
0
answers
173
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Sum of geodesic deviation around a triangle in curved spacetime?
So I was pondering about geodesic deviations and I'm confused about the following. Let's say I have $3$ geodesics $\gamma_1(t)$ , $\gamma_2(t)$ and $\gamma_3(t)$. I introduce a parameter $s$ such that ...
- 1,389
3
votes
3
answers
476
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Is General Relativity compatible with relative speeds bigger than $c$ between two inertial frames?
My question is motivated by a remark done by Tegmark in his book "Our Mathematical Universe". He says that GRT does not prove that relative speeds between material points are always smaller than c. It ...
- 81
3
votes
1
answer
56
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Detecting external 'forces' in an inertial frame
Disclaimer: Science noob here, I may not use all terms correctly.
I've read somewhere of the following situation: An observer is inside a room (elevator) with no ...
- 137
3
votes
2
answers
1k
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Galilean transformation in relativity
Assume flat spacetime in a general relativistic framework (or special relativity for that matter) and two observers $A$ and $B$, with non-vanishing velocity relative to each other. We know that they ...
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3
votes
2
answers
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Evidence for expansion of space [duplicate]
If I understand correctly, Einstein's theory of General Relativity predicted the expansion of space itself, and Hubble confirmed this prediction by observing the red shift of receding galaxies.
I ...
- 41
3
votes
0
answers
41
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Disappearing galaxies [duplicate]
According to the cosmological model of the expanding universe, the distant (diametrally opposite) galaxies have bigger and bigger relative comoving speed, and this speed (which is not a relative speed ...
- 81
2
votes
3
answers
553
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If I accelerate through space, can I say all stars gain kinetic energy?
Suppose I accelerate through empty space. Say all stars are small heavy marbles I can use to do work with by means of their velocity. Say I can let them smash into some generator that turns their ...
2
votes
1
answer
66
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How would we know whether a object is moving in deep space?
In deep space, there isn't anything we can compare our position with (According to my knowledge). In other words, we won't be able to define an origin so how would we know whether we are in motion or ...
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