Spheroid
A spheroid, or ellipsoid of revolution, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters.
If the ellipse is rotated about its major axis, the result is a prolate (elongated) spheroid, like an American football or rugby ball. If the ellipse is rotated about its minor axis, the result is an oblate (flattened) spheroid, like a lentil. If the generating ellipse is a circle, the result is a sphere. A spheroid has circular symmetry.
Because of the combined effects of gravity and rotation, the Earth's shape is not quite a sphere but instead is slightly flattened in the direction of its axis. For that reason, in cartography the Earth is often approximated by an oblate spheroid instead of a sphere. The current World Geodetic System model uses a spheroid whose radius is 6,378.137 km at the equator and 6,356.752 km at the poles.
The word spheroid originally meant an approximately spherical body, admitting irregularities even beyond the bi- or tri-axial ellipsoidal shape, and that is how it is used in some older papers on geodesy (for example, referring to truncated spherical harmonic expansions of the Earth).
Podcasts:
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by Prelude
After The Goldrush
by: PreludeWell I dreamed I saw the knights in armour coming saying something about
a queen
There were peasants singing and drummers drumming and the archer split
the tree
There was a fanfare blowing to the sun that was floating on the breeze
Look at mother nature on the run in the nineteen-seventies
I was lying in a burned out basement with a full moon in my eyes
I was hoping for a replacement when the sun burst through the skies
There was a band playing in my head and I felt like getting high
I was thinking about what a friend had said I was hoping it was a lie
Thinking about what a friend had said I was hoping it was a lie
Well I dreamed i saw the silver spaceships flying in the yellow haze of
the sun
There were children crying and colors flying all around the chosen one
All in a dream, all in a dream the loading had begun
They were flying mother nature's silver seed to a new home in the sun
Flying mother nature's silver seed to a new home in the sun