Current Moon Phase | How phases change | On the Moon | More Moon Resources
Though a satellite of Earth, the Moon is bigger than Pluto. Some scientists think of it as a planet (four other moons in our solar system are even bigger). There are various theories about how the Moon was created, but recent evidence indicates it formed when a huge collision tore a chunk of the Earth away.
[24 Hours of Chaos: The Day the Moon was Made]
Moon data (averages):
Diameter: 2,160 miles
Time to rotate: 27.3 days*
Orbit: 27.3 days*
Compared to Earth:
Mass: 1.2% of Earth's
Diameter: 27% of Earth's
Distance from Earth: 238,866 miles
How the Moon's phases change
Because it takes 27.3 days both to rotate on its axis and to orbit Earth, the Moon always shows us the same face. We see the Moon because of reflected sunlight. How much of it we see depends on its position in relation to Earth and the Sun.
Earth's gravity keeps the Moon in orbit, while the Moon's gravity creates tides on our oceans
On the moon
The Moon has almost no atmosphere, so a layer of dust -- or a footprint -- can sit undisturbed for centuries. And without an atmosphere, heat is not held near the planet, so temperatures vary wildly. Daytime temperatures on the sunny side of the Moon reach 273 degrees F; on the dark side it gets as cold as -243.
In June of 1999, reserchers discovered by accident that a huge cloud of sodium gas trails behind the Moon.
The Lunar Prospector in 1998 provided evidence of ice near the Moon's poles, perhaps as much as 6 billion tons of it.
Final fact
The Moon travels around the Earth at a little more than half a mile per second; its speed is slowing and the satellite is gradually moving away from Earth.
Photographs: NASA/NSSDC
Full Moon Fever
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