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A comment on Musk files to provide Internet service from space. Parent comment

Re:Musk files to provide Internet service from space by brian_ on Tuesday June 09, 2015 @10:53PM (#9689812)
My understanding of it is that when light passes through a medium, it does not do so in a straight line. So, while the actual speed of light remains constant, it takes longer to get from one end to the other.
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Re:Musk files to provide Internet service from space by paulvs on Wednesday June 10, 2015 @12:04AM (#9689973)
To be precise, light can travel through a medium in a straight line, but it bends when it passes from one material to another. The light bounces off the inner walls of the fiber in a zig-zag fashion as it propagates, so it cannot possibly travel at the speed of light. It depends on the index of refraction as mentioned.
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Re:Musk files to provide Internet service from space by Robin_Message on Wednesday June 10, 2015 @04:51AM (#9690717)
No, the speed of light decreases in a medium – in fact, the proportional decrease in speed is the refractive index of the material.

So much for it being constant huh?

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