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Originally posted by KnifeMissle
First of all, I understand the question and I think I have a reasonable explanation for it all. But I will save that for later. For now, let me address a few things...
There are many examples of things that travel faster than light. The scissor example is but one. They're all kind of contrived, especially the quantum examples, but here's another for you guys. You have a flashlight that shoots a straight beam (it could very well be a laser but I wanted to make the example simple). Now, put it in a circular room and spin it. You will see a dot on the wall and it will be moving. How fast will it be moving? Well, that depends on the radius of the room, doesn't it? Well, make the room arbitrarily big. What happens? You can make the dot move arbitrarily fast - faster than the speed of light, even. How about that? Can anyone explain that?
Like I said, I can explain it but I will save that til I see some more conjectures...
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Thats exactly like the example of shining a laser on the surface of the moon.
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Oh, and while I'm at it, let me address something someone said:
First, I can't believe you didn't state the obvious. Force is not the product of speed and mass, that's momentum...
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I didn't say that. I was quoting it from Lunchbox.
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Secondly, light has no rest mass but, since light is never at rest, this is not a problem. However, I would tend to agree that light has no mass only because of the definition of mass: the measure of inertia. It's hard to talk about the inertia of something that moves at a constant speed regardless of your frame of reference!
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When most people use the word "mass", they are reffering to invariant mass (rest mass) not relativistic mass.
As such, it is correct to say that light is massless.
If you wish to communicate the idea of relativistic mass, you must explicitly say it, i.e. light has a relativistic mass.