"Earth is the cradle of man, but man does not live in the cradle forever."
-- Konstantin Tsiolkovsky
| Orbital Elements | ||
| ||
| Mean distance from Sun | 149,597,870 km | = 1 astronomical unit |
| Perihelion distance | 147,090,000 km | = 0.9832 astronomical unit |
| Aphelion distance | 152,100,000 km | = 1.0167 astronomical units |
| Eccentricity of orbit | 0.0167 | |
| Period of orbit | 365.25636 days | = 365:06:09:10 = 31,558,150 seconds |
| Mean orbital speed | 29.79 km/s | |
| Minimum orbital speed | 29.29 km/s | |
| Maximum orbital speed | 30.29 km/s | |
| Physical Properties | ||
| ||
| Mean diameter | 12,742 km | |
| Polar radius | 6,356.755 km | |
| Equatorial radius | 6,378.140 km | |
| Oblateness | 1/298 | |
| Mass | 5.97223 x 1024 kg | |
| Mean density | 5.515 g/cm3 | |
| Rotational period | 0.997269 day | = 23.9345 hours = 23:56:04 = 86,164 s |
| Mean length of day | 24 hours | = 86,400 s |
| Inclination of axis | 23.45° | relative to the axis of its orbit |
| Gravity at surface | 9.78 m/s2 | |
| Escape speed | 11.2 km/s | from surface, at equator |
| Visual geometric albedo | 0.37 | |
| Mean surface temperature | 15°C | |
| Atmospheric pressure | 1 bar | |
| Atmosphere composition by volume | ||
| ||
| Nitrogen (N2) | 78% | |
| Oxygen (O2) | 21% | |
| Argon (Ar) | 0.93% | |
| Carbon dioxide (CO2) | 0.03% | |
| Neon (Ne) | 0.0018% | |
| Helium (He) | 0.00052% | |
| Methane (CH4) | 0.0002% | |
| Krypton (Kr) | 0.00011% | |
| Hydrogen (H2) | 0.00005% | |
| Xenon (Xe) | 0.0000087% | |
| ||
| Plus highly variable amounts of water. | ||
| Composition of the Earth as a whole by mass | ||
| ||
| Iron (Fe) | 34.6% | |
| Oxygen (O) | 29.5% | |
| Silicon (Si) | 15.2% | |
| Magnesium (Mg) | 12.7% | |
| Nickel (Ni) | 2.4% | |
| Sulfur (S) | 1.9% | |
| Titanium (Ti) | 0.05% | |
Moon
One large moon.
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Jeff Root
September 4, 2003