Ramblings about relativity

[TrueHeart]

Relativity is all about how light behaves, and from that some truth is differentiated from some myth. Light's behavior is particularly at issue because the cosmos is ever expanding... some of the very distant galaxies are receding from us at near light speed -- we find that true while looking in any direction.

 

Getting right into it, if a fleet ("The Fleet") of spacecraft left Earth and headed out into space, moving at a significant fraction of lightspeed, then how would light (and/or radio, EM) signals behave between us and them? And how would such signals behave amongst The Fleet members themselves?

 

Would a radio signal sent from Earth take extra time to reach The Fleet, because it is receding away? Yet the reverse is not true?? ie. signals from The Fleet will transit only the predetermined distance through Earth's fixed coordinate system? Who is actually receding from whom?? Does it depend on how Earth is moving with respect to a higher coordinate system -- some master cosmic coordinate system??

 

In a word, no, none of that is true. Ok, it's all true, relatively true. What's absolutely true is the denial of any fixed master framework serving as a medium for EM signal transmissions: EM signals find their own way, somehow transcendent of mortal ciphering. It's uncanny: we don't know the how but we know the how much. We realize now that light behaves relativistically, which means that every clock and every ruler in the world must cede something to accomodate the feat -- sorta.

 

In the scenario cited, The Fleet astronauts experience one thing while us Earthbound folk experience something altogether different, something that seems contradictory. By all reckoning, the astronauts witness their Fleet's signals to Earth move at fixed lightspeed with respect to The Fleet's native 3D coordinate system -- and by "native" I mean, "that x-y-z frame with respect to which The Fleet is stock still in space." Those astronauts... they witness their outgoing signals as requiring extra time to "catch up" to the receding Earth, while incoming Earth signals need only travel the predetermined distance from their release point. And all the calculations work out... no, there is no incompetence.

 

And wouldn't y'know? Earthlings can make the very same claim. By all reckoning, they witness EM signals behaving as if Earth's native 3D coordinate system is boss. Their outgoing signals require extra time to catch up to the receding space Fleet, yet incoming Fleet signals need only travel the predetermined distance from their release point.

 

This relativity carries over to within The Fleet itself (assuming it moves in a fixed formation): individual member craft can send and receive messages with one another as if their distance of separation were the sole influencing factor. Light and radio signals don't take longer to transit in one particular direction because of The Fleet's supposed motion "through space" -- that element is negated entirely.

 

And now the final concluding point. Isn't it great that light behaves this way? especially considering that many millions of distant galaxies are flying away from us at tremendous speeds. If light simply moved relative to Earth, or relative to some master cosmic coordinate system (with respect to which Earth is fairly still), then how could those (hypothetical) zillions of aliens who populate those myriad distant galaxies ever live, eh?? they couldn't!! They would live in a giant ever-distorted world, where a simple twisting of the neck means drastic changes in their view of the surroundings -- red-shifted in one direction and blue-shifted in the other. They would be burned alive by a single candle flame if its radiations were coming from the wrong side.

 

See also my modest treatise on the web.