I think the parallel between lensing and rotation is pretty good. You don't
want to call gravitational lensing by a mass gravitational lensing if the light
being lensed comes from that same mass, and the other guy doesn't want
to call rotation rotation if the thing rotating is also revolving around some
other object or point in space.

-- Jeff, in Minneapolis

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http://www.FreeMars.org/jeff/

"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"

"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves