[ARC5] Blackout ; Lend Lease and ARC-5's (OT)

[J. Forster]

This is basically correct, but ignores scattering.

Any light emitted in a direction above the horizontal gets scattered by
the atmosphere and especially dust and other particles. Modern cities are
visible by the glow in the night sky.

You don't need a direct line-of-sight.

In fact, it is very difficult to see the night sky anywhere along the east
coast.

-John

================


> There is a simple formula for estimating the horizon from any height on
> the
> surface of the Earth. R (range) = sq rt [2 r x h], where r is the radius
> of
> the Earth and h is the height of the observer's eye above the Earth's
> surface. So, if you are in the crow's nest with your eye at 100' above the
> Earth's surface, and assuming the Earth's radius is about 4000 miles, then
> the Range to the horizon is 12 miles. It's just plain Pythagoras' theorem.
> If the working lights in the shipyard are some height above the Earth's
> surface too, then do another calculation for the horizon from the ship's
> lights - then add the two values of R together. So, if the shipyard lights
> were also at 100', then the lights would be visible from a 100' crow's
> nest
> from 24 miles.
>
> 73 de Brian, VK2GCE.
>
> On Sunday, July 08, 2012 6:37 PM, Les Smith asked:
>
>
>> Thinking more about this, (how far distance you could see the
>> working lights in a ship-yard) I figure my memory is completely
>> wrong here.  It would be difficult to see the sun two hours away
>> (due to the curve of the earth).   It's good Henk isn't here,
>> he'd box my ears for mis-quoting him.  Then I WOULD be sorry.
>>
>> 73
>>
>> Les
>> [1]vk2bcu at operamail.com
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