Facts About The Moon

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Learn Something New About Earth's Moon

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Will man ever return to the Moon? That remains to be seen. Until then, here are interesting Moon facts about our favorite celestial body.

Facts About the Moon

Each night, we glance up at the Moon, but how much do we really know about it? Here are some fast facts about our Moon:

  • Diameter: 2,160 miles
    This is about the distance from Washington, D.C., to the Rocky Mountains.

  • Average Orbital Speed: 2,287 miles per hour
    This number is very close to the Moon’s diameter, making it the only known celestial body that moves through space at its own width per hour. This motion is readily visible from Earth, even to the naked eye, as the Moon shifts its position against the background stars.

  • Synodic Period, or Lunar Month: 29 days, 12 hours, 44 minutes, 2.8 seconds
    This is the average period from one new Moon to the next.

  • Rotation Period: 27 days, 7 hours, 43 minutes, 11.5 seconds
    This spin-time of the Moon on its own axis is identical to the time it takes the Moon to revolve around Earth, which is why the Moon always keeps almost the same face toward us.

  • Mass: 81.3 times smaller than Earth’s
    The Moon’s total mass is 500 quintillion tons.

  • Albedo (Reflection of Light): Approximately 0.12
    Just 12% of the sunlight striking the Moon is reflected; the Moon’s surface has about the same shininess as rich soil. By comparison, the albedo of snow is 0.75, and that of Jupiter, 0.51.

  • Magnitude (Brightness): -12.7 in full phase
    Each magnitude on the standard scale is 2.5 times brighter than the next; compared with the brightest star, Sirius, whose magnitude is -1.5, the Moon is more than 250,000 times brighter. The Sun, on the other hand, is about 400,000 times brighter than the Moon!

  • Surface Temperatures: Daytime, 235°F typically, 273°F maximum; nighttime, can drop to -275°F
    This day/night range of about 500°F is more than five times greater than what is found in extreme desert areas of Earth, but is typical of an atmosphere-less world.

  • Distance From the Earth: 238,857 miles (mean)
    Since the Moon’s orbit is an ellipse, there are distance variations of over 30,000 miles.

  • Surface Gravity: 5.3 feet per second
    On the Moon, an object would fall less than three feet in one second and about 11 feet in 2 seconds. On Earth, an object falls 64 feet in 2 seconds.

  • Escape Velocity: 1.48 miles per second
    To escape the Moon’s gravity, a rocket must achieve a speed of about 1.5 miles per second, or 5,328 miles per hour. To escape Earth, a rocket requires a velocity of nearly 7 miles per second, or 25,000 miles per hour. Scientists inform us that travel to the Moon will take 3 to 4 days each way for the foreseeable future.

Isn’t our Moon grand? See more about the Moon in our Moon Phase Calendar and Full Moon Calendar.

About The Author

Bob Berman

Bob Berman, astronomer editor for The Old Farmer’s Almanac, covers everything under the Sun (and Moon)! Bob is the world’s most widely read astronomer and has written ten popular books. Read More from Bob Berman

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