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I know that the speed of light is constant for some reason.
But why is it that when shining light from a spacecraft that is moving at (almost) the speed of this light, the speed of this light wouldn't seem to travel at (almost) twice the speed of light to an outside observer, or does it?
I also would like to know why the speed of light is constant?
Finally, I also would like to know why the speed of light considered the fastest speed possible? I read that there is no explanation, it is just a physical law of our universe but is there a possible explanation?