Why do clocks appear to run at different speeds when traveling at high speeds?

[branniganslaw]

I don't understand this: http://casa.colorado.edu/~ajsh/sr/timevbig_gif.html

if the mirror is moving fast enough, why won't the light just miss it? why is the light traveling towards at an angle instead of straight?

 

[tiny-tim]

welcome to pf!

hi branniganslaw! welcome to pf!

if the mirror is moving fast enough, why won't the light just miss it?

it won't, because it's the same light and the same mirror …

the picture is showing the same thing as seen by two differently-moving observers

 

[branniganslaw]

That makes more sense, but that site actually says that clock moved. http://casa.colorado.edu/~ajsh/sr/time.html

What bothers me is that when you move away from the clock, your perspective changes. Do these figures take that into account? http://en.wikipedia.org/wiki/File:Time-dilation-002.svg

 

[Janus]

That makes more sense, but that site actually says that clock moved. http://casa.colorado.edu/~ajsh/sr/time.html

If you were the blue dot, the light still just goes straight up to the mirror and straight down back, even in the second image. (as far as you can tell, you are not moving, the red dot. is.)
IOW, the second animation is according to the red dot. The same animation according to the blue dot would have his light going straight up and down, while the red dot's light follows the angled path off to the left.

 

[nitsuj]

tiny-tim said it.



For this example it helps me to think of these two "clocks" scenarios as being in:

Scenario 1 - the same "context" or "system".

Scenario 2 - separate "contexts" or "systems".

Imagine for scenario two, you are "riding along" with clock two. You have just entered a different world where clock two's light doesn't travel on an angle anymore. Now try and imagine what clock one's light would look like.

And that's no trick.