A Few Questions

[mattdd]

OK I have just got a few questions. They have probably been asked before, but I have looked and can't find the answers...

 

Question 1:

 

I understand that if something is completely stationary, then it moves through the time dimension at the speed of light..? So if I was sitting stationary, at the centre of the universe (assuming that the universe is all that there is, and its not itself moving in some other body), then all I am traveling through time as fast as is possible? Now my question is, when I stand still on earth, I am no longer stationary relative to the universe (because of the earths movement/rotation). So what percentage of my speed of light "allocation" is used up in movement when I am stood still on earth...? A pretty pointless question I guess, but I have always wondered...

 

Question 2:

 

Imagine a train is traveling is traveling at exactly 500,000,000 MPH (the number isn't important, just very fast) in a perfect straight line. Imagine on that train, there is a person with a torch. Now imagine there is someone standing on a platform watching this train. Because the train is traveling so fast, everything in the train would appear to be happening in slow motion as he observes it from his stationary perspective (as the man waves to him, he would see the wave in slow motion)...? So, from the stationary mans perspective, when the torch is turned on, would he see light traveling in slow motion too? Would he see the light traveling away from the torch slower than if he were to turn on a torch himself, stood on the platform?

 

Question 3:

 

This might be a stupid, pointless question, but it has always puzzled me. I am under the assumption that nothing can travel faster than the speed of light. Light travels 299,792,458 meters in a second. So imagine that I have an infinitely strong steel bar that is 300,000,000 meters long. It cant bend or warp. It cant be compressed in any way. Now, if I push one end of the bar, the other end will move instantaneously 300,000,000 meters away at the other end? If that is the case, has a force just been transmitted faster than the speed of light...?

 

 

Thanks for taking the time to read my questions

 

I look forward to hearing the answers

 

Thanks everyone

[Sisyphus]

OK I have just got a few questions. They have probably been asked before, but I have looked and can't find the answers...

 

Question 1:

 

I understand that if something is completely stationary, then it moves through the time dimension at the speed of light..? So if I was sitting stationary, at the centre of the universe (assuming that the universe is all that there is, and its not itself moving in some other body), then all I am traveling through time as fast as is possible? Now my question is, when I stand still on earth, I am no longer stationary relative to the universe (because of the earths movement/rotation). So what percentage of my speed of light "allocation" is used up in movement when I am stood still on earth...? A pretty pointless question I guess, but I have always wondered...

 

There is no such thing as stationary in any absolute sense. If you are stationary in one frame of reference, then you are moving in all others. And, there is no reason to choose one frame of reference over another besides convenience - the math works exactly the same. (e.g., when doing calculations about the motion of a car, a stationary Earth is generally preferable. On the scale of the solar system, a stationary Sun is generally preferable.)

 

So, how much time/space distortion you are experiencing depends entirely on what frame of reference it is measured from.

 

Also, the universe does not have a center. (But that's a whole other can of worms and not important to your question.)

 

Question 2:

 

Imagine a train is traveling is traveling at exactly 500,000,000 MPH (the number isn't important, just very fast) in a perfect straight line. Imagine on that train, there is a person with a torch. Now imagine there is someone standing on a platform watching this train. Because the train is traveling so fast, everything in the train would appear to be happening in slow motion as he observes it from his stationary perspective (as the man waves to him, he would see the wave in slow motion)...? So, from the stationary mans perspective, when the torch is turned on, would he see light traveling in slow motion too? Would he see the light traveling away from the torch slower than if he were to turn on a torch himself, stood on the platform?

 

No. Light always moves at the same speed, from every perspective, in every frame of reference. The man on the train will see the light moving at C (the speed of light) relative to himself. The man on the platform will see the light moving at C relative to himself.

 

Note that they will not agree on how fast the light is traveling relative to one another.

 

Question 3:

 

This might be a stupid, pointless question, but it has always puzzled me. I am under the assumption that nothing can travel faster than the speed of light. Light travels 299,792,458 meters in a second. So imagine that I have an infinitely strong steel bar that is 300,000,000 meters long. It cant bend or warp. It cant be compressed in any way. Now, if I push one end of the bar, the other end will move instantaneously 300,000,000 meters away at the other end? If that is the case, has a force just been transmitted faster than the speed of light...?

 

This thought experiment just shows that there is no such thing as an incompressible object. The upper limit to how fast the force can be transmitted through the bar (via a shock wave) is at the speed of light. In reality, no material even comes close to that limit.

[timo]

This thought experiment just shows that there is no such thing as an incompressible object.

Strictly speaking that is not what comes out of this thought experiment. What it does say is that if there was such a rod (and if it was light enough that you can still push it) you could pass information faster than with a light beam. Saying that the assumptions made are not compatible with reality is a different statement, not a result of the thought experiment presented. Edited July 27, 2010 by timo

[mattdd]

Thank you very much for all the answers