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Oct25-11, 02:17 PM
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Quote Quote by Dimosthenis S View Post
Hi Darktangent1.... This is my first, so ...hi in general :) Well, I must say that I did not follow your example fully, but the answer might well be that when you are talking about the speed of light being the same in all inertial frames, what that basically means is that the light has its own speed in a specific space.... this is not at all curious, it is as simple as the speed of sound, which is the same in given conditions, regardless if e.g. you are in a airplane or walking in the street.... Light travelling is just another phsycial phenomenon, no magic here.....
Well, no, the speed of light in all inertial frames is defined to be the same, not measured. But the speed of sound can be measured in any situation, it doesn't have to be defined in order to make a meaningful Frame of Reference.
Quote Quote by Dimosthenis S View Post
....And something else, please let me clarify one thing: When I am saying that the speed of sound is the same, no matter if you are inside an airplane or walking, I am just referring to the speed of those two; the air, as a medium, is supposed being homogeneous and not moving.... And then, that means also, that if the airplane has a sealed cabin, the environment inside the airplane is moving in a different speed than the -stand still- air of the outside enviroment, and so the speed of sound inside the cabin is in a world on its own; that brings of course the question: are there sealed environments inside our enviroment, where electgromagnetism behaves independetly? And if so, what are the physical constraints that make the said enviroment sealed, like e.g. the body of the airplane? Similarly, are there any other outer enviroments, where electromagnetism behaves differently (the same as we are talking about atmospheres - that reads mediums for the sounf to propagate - existing in planets other than earth)?.... Frankly, I am not sure if I can answer, right now ( :) ), since we must have first to find out a way, if there is any of course, to measure such things......
No, there are no sealed environments that cause light to behave differently than it would in an unsealed environment. And this shows a difference between light and sound. In order to get sound to travel at the same speed in a moving environment (like an airplane) as it would outside on the ground with no wind blowing, you have to seal the air inside from the air outside so the air inside will seem like it is stationary with respect to the airplane. With light, you don't have to do that. Even out in the open, as long as the airplane, or spaceship, or whatever, is traveling at a constant velocity (and we are ignoring the effects of gravity), it will appear to have exactly the same characteristics as any other similar situation.