All Questions
Tagged with special-relativity observers
813
questions
108
votes
12
answers
15k
views
How can time dilation be symmetric?
Suppose we have two twins travelling away from each other, each twin moving at some speed $v$:
Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin ...
67
votes
10
answers
172k
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Would time freeze if you could travel at the speed of light?
I read with interest about Einstein's Theory of Relativity and his proposition about the speed of light being the universal speed limit.
So, if I were to travel in a spacecraft at (practically) the ...
52
votes
8
answers
14k
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How is the classical twin paradox resolved?
I read a lot about the classical twin paradox recently. What confuses me is that some authors claim that it can be resolved within SRT, others say that you need GRT. Now, what is true (and why)?
- 3,711
50
votes
5
answers
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Could I, within my lifetime, reach any star I wanted if I went fast enough?
Disclamer: I'm not talking about FTL travel here. I'm also not talking about any weird space warping mechanics like wormholes and such.
I've always thought that if a star was 4 light years away, then ...
- 621
36
votes
3
answers
9k
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Is there a frame of reference in which I was born before I was conceived?
I'm struggling to understand the relativity of simultaneity and position.
If my conception and birth are separated by time but not space, a frame of reference in which my birth and conception are ...
- 740
33
votes
4
answers
9k
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How does a photon experience space and time?
To an an external observer it appears that time has stopped for photon. But this relation is reflexive, so for an observer travelling with the photon it appears the universe has stopped everywhere.
...
- 13.1k
30
votes
5
answers
3k
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What do you really see on a line of clocks as you pass by them at high speed?
According to my understanding of SR, if I travel at 0.8c relative to a line of clocks, I should see the clocks in front of me going 3 times faster than my own, and those behind me going 3 times slower ...
- 1,903
27
votes
6
answers
6k
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Is time dilation due to the travel time of light?
I'm trying to think about special relativity without "spoiling" it by looking up the answer; I hope someone can offer some insight - or at least tell me I'm wrong.
Suppose I have an ordinary clock ...
- 1,365
27
votes
5
answers
5k
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Hole-and-nail paradox in special relativity
Yesterday we started relativity on our physics class, and my professor taught us a few concepts. We did some examples on how things changed by looking them from different reference systems, and a ...
- 381
26
votes
8
answers
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In the twin paradox does the returning twin also come back permanently length contracted flatter than the twin on Earth?
This video from Brian Greene suggests this is so:
https://www.youtube.com/watch?v=2sZUNud6rRw&list=PLj6DWzIvBi4PFDXCCV1bNhVUgDLTwVbFc&index=60
It shows if you stop a pole in the barn (...
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25
votes
8
answers
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In the theory of special relativity speed is relative so who decides which observer’s time moves slower? [duplicate]
If for example we have 2 people one moving in speed v relative to the other, according to special relativity the time passing for the moving person is slower than for the stationary person. However ...
- 375
25
votes
2
answers
3k
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Do echo-locating bats experience Terrell effect?
At relativistic speeds there is an optical effect called Terrell rotation causing objects passed by to seemingly rotate.
As bats use sound rather than light when echo-locating, at what degree would ...
- 358
24
votes
10
answers
7k
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What are the mechanics by which Time Dilation and Length Contraction occur?
What are the mechanics of time dilation and length contraction? Going beyond the mathematical equations involving light and the "speed limit of the universe", what is observed is merely a phenomenon ...
- 241
24
votes
5
answers
5k
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Can someone conceptually explain time dilation?
Can someone intuitively explain how physically time dilation happens?
Please don't explain about the invariant speed of light and the mathematical background, I am familiar with that. I just can't ...
- 449
23
votes
5
answers
3k
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What is physically different about a moving vs still object in space?
If I have two asteroids. One dead still in space and one whizzing by at 10,000mph. What is the difference between the two, physically?
If I freeze time and look at the two of them - what differences ...
- 341