Morberticus
iyamaneenja
A <-- B --> C
Suppose you have two flashlights that are duct-taped together back-to-back (B) in a deep vacuum in outer space.
You flick a switch that powers them both simultaneously.
What is the difference between the speed of one of the photons from A (the light headed in the direction of A from the flashlight facing that direction) compared to that of one of the photons from C (headed in the complete opposite direction).
Prove your answer/s. Their speeds are identical. Their velocities aren't.
What she said...erm, their relative speed is 2*c. =)
Prove our answers? Erm, the universal constancy of the speed of light is pretty much one of the most famous
postulates of special relativity (...kinda has to be since there are only 2). This assumption is actually is what leads to us (re-)derive the Lorentz transformations. The proof is really more in the experimental confirmation that this appears to be the case.
Which is why I brought along my handy-dandy Michelson interferometer! Doo dee doo! *Checks it out* Yep, it's constant...in all reference frames...I just checked...you don't have to worry.
wink
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