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Not Quite a Sphere
The Layers Beneath
11 other sections not shown
air pressure angle astronomers atmosphere aurora average density belt calculate called cent center of gravity circle circumference Columbus cosmic rays craters crust cubic miles curve degree of arc diameter distance DOUBLE PLANET dust earth earth's surface ellipse equator equatorial bulge equinoxes Eratosthenes escape velocity exosphere farther feet flattened foci gm/cc gravitational pull heap of water heat heavenly bodies hemisphere ionosphere iron core layer lead ball light lines of force lithosphere magnetosphere major axis mantle mass measure meteorites miles a second miles an hour miles height Moho discontinuity moon moon's rotation motion mountain move Newton north celestial pole north magnetic pole north pole object oblate spheroid ocean orbit parallax particles pendulum perfect sphere perigee planet radiation reach rock rockets satellite scientists sea level seemed shadows side six-foot model slowly south pole space speed spinning square inch stars subtends swing temperature thin tides tiny troposphere turned volume