# Tag Info

### How can coordinates be meaningless in General Relativity?

The quote that prompted this question is my fault, so perhaps I should answer this. In context I wrote [C]oordinates are meaningless. You can calculate any physically meaningful quantity using any ...
• 28.2k

### How can coordinates be meaningless in General Relativity?

Coordinates are not meaningless. But perhaps a better word would be unimportant - in the sense that the physics does not care what coordinate system you use and all measurements that you could make ...
• 135k

### How can coordinates be meaningless in General Relativity?

Aidan Beecher asked: "Why isn't it possible to find any choice of coordinates that correspond to a particular observer, like in special relativity, where it is possible to Lorentz transform into ...
• 12.5k

### Why does an accelerated clock record fewer events?

No, you misunderstand what is happening. The difference in time is a consequence of the geometry of spacetime. It might help to consider an analogy with 3d space. Suppose you drive your car in a ...
• 26.7k

### Why does an accelerated clock record fewer events?

Your first mistake is here: "The clock is accelerated and its tick rate is observed to decrease by all observers relative to the tick rates of their local clocks." After a clock changes ...
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### Does special relativity also imply that speed of sound is constant for all observers irrespective of their relative motion?

The statement is that the laws of physics are the same in both frames, not that a specific solution will be the same in all frames. The laws of physics are based on differential equations. To get an ...
• 105k

### What will going near the speed of light would look like?

If A is moving toward B, he will see B's clock ticking in "fast forward", but will realize this is partly because B keeps getting closer, so light from each tick of B's clock arrives faster ...
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### Does a pendulum violate general relativity?

You are wrongly confusing two separate effects, namely the curvature of spacetime and the effect that curvature has on the performance of a device that measures time.
• 26.7k
Accepted

### Is gravitational length contraction only in one direction?

When it lands on the surface, gravity will compress it. This is not what gravitational length contraction is about. If we have a cube on the ground it will be slightly shorter due to the compression ...
• 7,491

### Does special relativity also imply that speed of sound is constant for all observers irrespective of their relative motion?

No. The speed of light is more closely related to the structure of spacetime than anything else. Traveling along null curves, a photon moves at the highest speed it can while staying on “causal” paths,...
• 1,575
1 vote
Accepted

### Does special relativity also imply that speed of sound is constant for all observers irrespective of their relative motion?

The speed of sound is not constant for all observers, but this does not contradict the fact that the laws of physics are the same in all reference frames or imply that you can detect your absolute ...
• 7,491
1 vote

### Why does an accelerated clock record fewer events?

This had me confused: The clock also continuously records its readings so that at the end of the experiment there is a single record upon which all observers will agree IMO, That's an unnecessary ...
• 15.7k
1 vote

### Why does an accelerated clock record fewer events?

The physical properties like frequencies of atoms are of course valid in the proper time of the object. One well known effect is the detection of muons. They are formed about twelve thousand meters in ...
• 16.8k
1 vote

### What will going near the speed of light would look like?

If you really mean 'see', as in experience in real time with their eyes, then they won't see anything. If I pass you at the speed of light, I will be at an easily visible distance for too short a ...
• 26.7k
1 vote

### Does a pendulum violate general relativity?

You are confusing two notions which are totally different : the gravitational potential : the deeper into a (negative) gravitational potential, the slower the clock. Whatever method you use to ...
• 4,469

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