Aye, penumbra; solar light pressu(was Correcting my own math -- CORRECTED)

On Feb 3, 2012, at 7:45 PM, hitssquad wrote:

> The 109x diameter spacing I cited is the maximum length of the umbra:
> http://en.wikipedia.org/wiki/Umbra
>
> "The umbra (Latin for "shadow") is the innermost & darkest part of
> the shadow, where the light source is completely blocked by the
> occluding body. An observer in the umbra experiences a total eclipse."
>
> The length of the umbra changes as the distance of the earth to the
> sun changes. The closer the earth is to the sun, the shorter the
> umbra. The farther the earth is from the sun, the longer the umbra
> -- up to a maximum of 109X the diameter of a circular occluding
> object (at an Earth-Sun distance of about 94.5 million miles, which
> occurs in current times in June every year).
>
> Therefore, the larger the SPS, the larger the umbral length. A 2 km
> diameter SPS casts a 218 km umbra. A 20 km diameter SPS casts a
> 2,180 km umbra.

Wait a minute. The plane of GEO is inclined 22+ degrees to the
ecliptic. So how is it that SSPs eclipse each other even at the
equinoxes?