"uncle arnie" wrote in message
...
On Thu, 30 Dec 2004 21:26, tianli posted to
rec.radio.shortwave: %MM


0.558 miles.

About 900 meters.

Is that in empty space or in an atmosphere?

speed of light or electricity is constant, never varies.

Not so. The constant applied to the speed of light applies only to the speed
of light in a vacuum. It slows down considerably when it hits atmosphere,
and much more when it hits water (this is what causes the refraction you see
when you put a straw in a glass of water)

Electricity is even more affected by the medium in which it travels. This
includes radio waves. Open atmosphere radio waves travel at ~95% of light
speed once they hit an antenna, some coax slows them down to as little as
60% of the speed of light (velocity factor)