Quote:
Originally Posted by Cd
I found that last bit about the steel rod to the Moon example to be absolutely fascinating !
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As a tangent to that tangent, that's the basic theory behind the relativity of time, and time travel.
In the steel rod example, the "information" about being pushed on one end could only travel as fast as the speed of sound in that material as molecules push into their neighboring molecules, which then push into their neighbors.
If the sun just instantly vanished, we would continue enjoying sunshine for 8 more minutes, and would have no way to know it had disappeared until the last of the light traveled the 8 minutes to us. Even stranger, the earth would continue to orbit around where the sun was for those 8 minutes, because even gravity propagation can't exceed the speed of light.
If you could hitch a ride on a photon of light, your journey would begin and end exactly at the same moment. From the perspective of the first photons emitted at the beginning of the universe billions of years ago, zero time has elapsed.