The question is not meaningful. If the speed of light were decreased, then the structure of everything else in the Universe would be changed such that everything else would move slower, too, by the same factor, so it would look exactly the same.
flyboy:
There’s a decent explanation incorporating what everyone has said using the train thought experiment here . Basically, a woman standing on the middle of a train is passing a station with a man standing on the station. Lightning strikes the train–one bolt in the front of the train, one bolt in the back, and leaves marks on the front and back of the train, as well as the ground. To the man, it (for this thought experiment) happens at the same time. He can go out and measure the marks on the ground and they’ll be the exact same distance to where he was standing on the platform. But the woman will have seen the bolt that hit the front of the train strike first, since she’s moving toward the light from that bolt, and away from the light from the bolt that hit the rear of the train. So time is different for her. Not only that, but length is different, too–the train, while moving, will for her be a different length than it is for the man on the platform. The link explains it better than I can.
She has to be wearing a red shift, surely?
Pduol:
There has been some (I think) good answers in this thread. But I’m still befuddled about the whole thing. My mind just won’t wrap around it. Does anyone have any links that can, as simply as possible, explain the whole relativity and speed of light thing to a non-scientist, non-physicist, layman type person?
How about in words of four letters or fewer?
naita
May 6, 2010, 11:59am
44
Polycarp:
Relative to the speed of light, it is. That’s the point behind the theory of relativity. You know all those physics formulas that include “v” in them? Per Einstein – and he could prove it mathematically, and physicists have demonstrated it with real-world proofs – that “v” is actually subject to a correction factor of the square root of a number that is one minus v[sup]2[/sup]/c[sup]2[/sup] – for “normal”, non-relativistic velocities, that fraction approximates zero and the resulting number pproximates one. But as “v” approaches “c”, it deviates farther and farther from “what it oughta be” by everyday experience – because everyday experience doesn’t deal with the force or weight or duration of things traveling at substantial fractions of “c”.
No. “v” remains the same, time and space changes. If a spaceship A from planet B travels at 0.5c away from the planet, both the observer on planet B and the observer on the spaceship A agree that the difference between their velocities is 0.5c.
Add another spaceship C traveling at 0.5c relative to A (along the same line) and ask how fast it’s moving relative to planet B and you have to apply relativistic corrections. Or ask about some of the properties that are dependent in a simple way on velocity in Newtonian mechanics, like kinetic energy and momentum.
Jake
May 6, 2010, 7:57pm
45
I agree. Slight hijack: If the Universe had only one body in it, how would one determine if it was moving or not?
I don’t think you could. I think you could determine if it was accelerating or not, but I don’t think you could determine if it was moving.
If you were there to observe that one body there would then be two, so it would be relative to you.
Jinx
May 7, 2010, 2:23am
48
These are not native to our land! Are you suggesting foreign light migrates!?!
