[ntp:questions] Questions about joining pool.ntp.org

David Woolley david at ex.djwhome.demon.invalid
Tue Aug 30 22:48:55 UTC 2011

Richard B. Gilbert wrote:

> The speed of light and/or electrical signals, radio waves, etc. are 
> *approximately* the same!  The speed of an electrical signal in copper 
> wire is slightly less than the speed of light in vacuum!  It will be 
> different again if the wires are aluminum rather than copper.  If you 

The signal in a cable travels (as a guided electromagnetic wave) in the 
gap between the conductors.  The insulation material makes a lot more 
difference than the conductor, e.g., for coaxial cables with solid 
polyethylene insulation, it is about 0.67, but with foamed polyethylene 
it is more like 0.8.  For pure air, the velocity factor is close to unity.


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