- #1
FranzDiCoccio
- 342
- 41
Hi,
I was browsing the internet for interactive simulations illustrating special relativity concepts. It seems to me that those in this http://kcvs.ca/concrete/visualizations/special-relativity are mostly nice and clear, although not very "chrome-friendly" (I have to use firefox to play their swf files).
I'm having some trouble with their visualization of http://www.kcvs.ca/site/projects/physics_files/specialRelativity/synchClocks/synchClocks.swf, though.
There are several things that seem really strange to me.
Now I can think of putting a second clock on the rocket that is identical to the first, but orthogonal to it. I believe that the departure and arrival of the photons in both clocks can be made simultaneous (the two "photon guns" can be put very close to one another). So both clock tick simultaneously (in the rocket frame _and_ in the lab frame).
This means that the "horizontal" clock should be seen as shorter than the "vertical" clock, by a factor [itex]\sqrt{1-v^2/c^2}[/itex].
Now if the second clock has to tick simultaneously with those in the lab, it should be _really_ shorter (as opposed to just contracted).
Perhaps the authors of the simulation are focusing on the _real_ length of the clock, and not on its length as it appears from the lab. That is, they are choosing not to represent length contraction.
That would probably work, although I find it a bit confusing.
Anyway, I'm pretty sure that the photon in the traveling clock does not hit the mirror at the same time as the stationary clocks, and does not slow down, as depicted in the app. Since the rocket is traveling, it takes more time to reach the front of the rocket. This time is compensated by the shorter time on the way back. That is, the overall journey of the photon should be synchronized, not each leg.
Any insight on this is really appreciated.
Thanks a lot
Franz
I was browsing the internet for interactive simulations illustrating special relativity concepts. It seems to me that those in this http://kcvs.ca/concrete/visualizations/special-relativity are mostly nice and clear, although not very "chrome-friendly" (I have to use firefox to play their swf files).
I'm having some trouble with their visualization of http://www.kcvs.ca/site/projects/physics_files/specialRelativity/synchClocks/synchClocks.swf, though.
There are several things that seem really strange to me.
- the behavior of the "photon" in the moving light clock seems wrong. As far as I understand the photon in the rocket should move always as fast as the ones in the lab frame. So I'd expect that it takes a longer time to go from the rear of the rocket to its front, and a shorter time in the opposite direction. Instead it takes the same time for both paths.
- In order to do the above, the photon slows down when traveling towards the rear end of the rocket, like there was a Galilean composition of its velocity and that of the rocket. That feels really strange.
- When the factor [itex]\sqrt{1-v^2/c^2}[/itex] is punched in the clock length field, the traveling clock is synchronized with the stationary ones. But then I do not understand the meaning of the rescaled length. I think that, in order to be synchronized with the stationary clocks, the traveling clock should be seen as even shorter. That is, the factor should be [itex]1-v^2/c^2[/itex].
Now I can think of putting a second clock on the rocket that is identical to the first, but orthogonal to it. I believe that the departure and arrival of the photons in both clocks can be made simultaneous (the two "photon guns" can be put very close to one another). So both clock tick simultaneously (in the rocket frame _and_ in the lab frame).
This means that the "horizontal" clock should be seen as shorter than the "vertical" clock, by a factor [itex]\sqrt{1-v^2/c^2}[/itex].
Now if the second clock has to tick simultaneously with those in the lab, it should be _really_ shorter (as opposed to just contracted).
Perhaps the authors of the simulation are focusing on the _real_ length of the clock, and not on its length as it appears from the lab. That is, they are choosing not to represent length contraction.
That would probably work, although I find it a bit confusing.
Anyway, I'm pretty sure that the photon in the traveling clock does not hit the mirror at the same time as the stationary clocks, and does not slow down, as depicted in the app. Since the rocket is traveling, it takes more time to reach the front of the rocket. This time is compensated by the shorter time on the way back. That is, the overall journey of the photon should be synchronized, not each leg.
Any insight on this is really appreciated.
Thanks a lot
Franz