MadSci Network: Physics |
It Actually doesn't do either: it's created moving at 3E8 km/sec relative to any and all inertial reference frames and continues at that speed until it's destroyed. Why does it act this way? I don't think that anybody actually knows, but it appears to be one of the fundamental features of the nature of the world that it's that way -- kind of like "why does force = mass X acceleration"... it just IS. In some cases, it looks like light is being accelerated in a way -- when a beam of light passes near a really heavy object, like a star. When that happens, the beam appears to be bent in the direction of the star by a small amount. When it moves further away from the star, it snaps back into its original direction. Since it usually requires a force and an acceleration effect to make something move -- in this case, perpendicular to the original direction -- you might think that it's actually being accelerated. But that would be wrong: what's actually happening (or so we think) is that the really heavy thing is actually warping space -- sort of like the lines on a sheet of graph paper getting wavy so that if you drew along any single line, it would squiggle a bit -- and the light is just following the bent space-time continuum. Why does space work this way? Unfortunately, the answer is again that it's just the way it seems to work in our four-dimensional universe. Hope this helps! Steve Guch
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