On Thu, 12 May 2005 at 14:29:01 in message
NKJge.73931$NU4.3092@attbi_s22, Grumman-581
wrote:
"Antoņio" wrote in message ...
I'm not sure of what that remark means.
The earth is round... Radio travels line of sight, which means a straight
line...Draw a large circle with a protractor... Choose a point on the
circumference at the top of the circle... Draw a line tangent to the circle
through this point... The line is horizontal... If an object is above this
line, it will be able to 'see' the original point, if it is below the line,
but above the circumference, it will not be able to 'see' the original point
since the body of the circle (i.e. the earth) is getting in the way of the
signal... The greater the distance the object is above the circumference of
the circle, the more of the circle it is able to 'see'...
Now, extend this concept into three dimensions...
There is a very simple formula for the distance to the horizon from a
given height above the surface for a smooth sphere of 4000 miles radius.
Height (Feet) Distance (miles)
0 0.0
6 3.0
20 5.5
50 8.7
100 12.3
150 15.1
500 27.5
1000 38.9
2000 55.0
4000 77.8
8000 110.1
16000 155.7
32000 220.2
64000 311.4
128000 440.4
256000 622.8
The real earth is not of course that flat except over the oceans! Also
the further away you go the closer the horizon distance gets to being
the same as the height. It is obvious that from the moon you can almost
see the entire hemisphere.
--
David CL Francis
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