Clocks running slower is an illusion

[Rasalhague]

Oh, I see. I'll have to read up more on Epstein diagrams. Just found another link here:

http://www.relativity.li/en/epstein2/read/

I've met the idea of 4-velocity, but haven't really looked at alternative visualisations to Minkowski's yet.

 

[YellowTaxi]

Where two frames are moving relative to each other and remain strictly inertial (no acceleration) then perhaps in some sense the mutual time dilation is illusional because there is no absolute way to determine which clock is running slower than the other.

I don't think that's true kev. You could video tape (or digitally record) the action going on inside a close to c spaceship then examine it later when the ship is back on earth. Or transmit the digital data as a short burst of information (to avoid doppler complication). The ticking of time observed would be absolute, and should according to SR be equal to 1s/s - ie the same as on earth.

The ticking of time when observed through an Earth based stationary telephoto camera tracking the spaceship occupants throgh a side window should be time dilated acording to SR. So theoretically it could be tested - just not with todays technology, since we can't get spaceships close enough to c that's all.