Time Dilation Gamma Factor: New to STR, Confused?

[tomz]

i am comletely new to STR, and have just finish reading time dilation. (gamma factor)

but i am confuse why to illustrate the factor, light always travel prependiculer to the motion of the "train"

i try to apply the same thing when light travel along the motion of the train, then i got gamma=1/(1-v/c) rather than 1/(1-v^2/c^2)^0.5

can anyone help me out of the confusion?

thanks very much

 

[ghwellsjr]

Just like when you track the course of the light flash bouncing between two mirrors that are placed at right angles to the direction of travel, you have to track the light flash between two mirrors along the direction of travel. Keep in mind that the mirrors in this case will be closer together by a factor of one over gamma due to length contraction.

I made an animation that illustrates time dilation and length contraction in relation to a "circular light clock" for a moving observer. Because the observer is moving, his circle of mirrors moving along with him is contracted along the direction of motion and takes the form of an oval or ellipse, showing length contraction. When he sets off a flash of light, it forms an expanding circle of light which hits the different parts of the mirror at different time but when the reflections all return to him, they arrive at the same instant of time, which takes longer than if he had been at rest, showing time dilation.

Here is a link to the animation:

 

[GrayGhost]

I made an animation that illustrates time dilation and length contraction in relation to a "circular light clock" for a moving observer ... Here is a link to the animation:

Very good ghwellsjr. I'm curious, how's come you opt'ed not to show the outbound wavefront for the moving observer? Just didn't want to clutter the figure maybe?

GrayGhost

 

[ghwellsjr]

I thought I did. Isn't the expanding blue circle the outbound wavefront?