The Double PlanetDiscusses the smallest, most distant, and most mysterious planet in our solar system, its discovery, its peculiar orbit, and its recently discovered satellite. |
Contents
A Sphere | 13 |
Not Quite a Sphere | 25 |
The Layers Beneath | 41 |
Copyright | |
11 other sections not shown
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Common terms and phrases
air pressure angle astronomers atmosphere aurora average density 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 constant gravitational pull Greek heap of water heat heavenly bodies hemisphere Hipparchus hydrosphere ionosphere iron core layer lead ball light lines of force lithosphere major axis mantle mass measured 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 ocean parallax particles pendulum perigee radiation belts reach rock rockets satellites scientists sea level seemed side six-foot model slowly south pole space speed spinning square inch stars stratosphere subtends swing temperature thick thin tides tiny troposphere turned volume word meaning