On Jan 17, 2013, at 11:23 AM, retired mainframer <[email protected]> 
wrote:

> Don't both
> electricity and light move at c?

In a vacuum, light moves at c. In a fiber optic cable, you divide c by the 
index of refraction. That's usually in the range of 1.5, so the light is 
traveling about (2/3)c.

The speed of electrical signals is a bit more complicated. It's been almost 30 
years since I took electromagnetism so I'm not going to try to explain it; I'm 
sure I'd get it wrong. It will be less than c too, though.

-- 
Curtis Pew ([email protected])
ITS Systems Core
The University of Texas at Austin

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