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Post by carnyx on Oct 11, 2010 19:38:39 GMT 1
However, whilst observers always see their own light as travelling at the speed-of-light; even when travelling in aircraft ..... would those same observers always ear their own sounds travelling at the speed-of-sound?
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Post by abacus9900 on Oct 11, 2010 19:45:02 GMT 1
However, whilst observers always see their own light as travelling at the speed-of-light; even when travelling in aircraft ..... would those same observers always ear their own sounds travelling at the speed-of-sound? No, because if you recall, when you have watched some event like a cricket match, for example, you see the player striking the ball and then, a bit later, you hear the sound. Obviously, the further away you are from the player the longer the sound tales to arrive at where you are. The same thing happens in lightening, remember?
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Post by olmy on Oct 11, 2010 22:32:20 GMT 1
Well, what I meant was that light always travels at the same speed regardless of the frame of reference of the observer. That's correct, isn't it? It is very odd though, and I wonder if the answer will ever be known. It is as if, to maintain the light speed limit a trade-off between space and time takes place where time must slow down in order for two inertial frames of reference to see light as the same speed. Why isn't it much simpler where an absolute time rules everywhere in the universe? Things would be much simpler and Newton would have been correct! I think you've got it and yes, it's 'odd' (counter-intuitive). As I said, I can't answer the question as to why it is like that and not otherwise but that question could be asked of anything we find. Olmy, is it true, at least in theory, that if you could exceed the speed of light you could travel back in time, or is this just an 'old wives tale?' Well, if you simply plug v > c into the SR time dilation equation, the time duration becomes imaginary, rather than negative. In the context, I'm not even sure what 'travel faster than light' would mean. Given that the separation would be space-like, you could always find a frame in which the traveller would arrive before it departed and another one in which it would happen the conventional way around....
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Post by carnyx on Oct 11, 2010 22:36:58 GMT 1
abacus.. the local speed-of-sound is around 5 seconds/mile both on your cricket field, and also inside a car. So when the passenges hear the driver's horn it sounds OK to them. But to pedestrians on the road ahead they will hear it later than the driver thinks. If he was driving at over Mach 1 they would not hear it at all, until he was on them.
But ATD is not just a time-delay thing due to propagation speed and relative velocities is it? For those two clocks spaced one foot vertically, that would just give a fixed time delay.
For ATD those two clocks would have to be going at different speeds, right?
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Post by abacus9900 on Oct 11, 2010 22:52:50 GMT 1
It's a question of relative motion, isn't it? Clocks spaced one foot vertically matching the speed of the car would experience the same arrival of sound.
Light is not sound carnyx. Huge difference. Light is somehow more fundamental and more mysterious.
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Post by speakertoanimals on Oct 12, 2010 15:38:55 GMT 1
It's not light that is odd, but space and time. The cosmic speed limit that we happen to call the speed of light would still exist, even if there wasn't anything that happened to travel at that speed. The existence of this universal speed limit has effects on objects that travel at LESS than this speed.
So, even if light were found to travel at a speed which was a millionth of a percent below what we call lightspeed, it wouldn't mean that relativity was wrong, or that we couldn't test it, or that the cosmic speed limit didn't still exist.
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