Kaguya-hime and the Solar System 91
Earth
Size Equatorial radius of 3,963 miles, or 6,378 km
Mass 5.976 x 10
24
kg
Surface gravity 9.82 m/s
2
Satellites 1
Mean distance from the Sun 1 AU (approximately 149.6 million km)
Orbital period 1 year (approximately 365.25 Earth days)
Rotation period 1 Earth day (approximately 24 hours)
What’s It Like There?
Our home planet is often called Mother Earth, but 4.6 billion years ago when it was formed,
it was not the kind of environment in which living creatures thrived. Its surface was covered
by molten rock known as magma, and water only existed in gaseous form (water vapor).
Also, the atmospheric pressure was approximately 300 times greater than it is now. Mars
today is an environment much more conducive to life than Earth was then.
Earth’s environment became moderate enough to support life as we know it approxi-
mately 550 million years ago. This was around the beginning of the Paleozoic Era, when the
number of species began to increase rapidly. From the perspective of the history of Earth,
that’s the very recent past.

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