The title of this article may seem like a silly question. After all, any grade-schooler could you the answer is: No. The Earth only has one moon. But, according to astronomers, their answer would be incorrect. The Earth does, in fact, have more than one moon at any given time.
How Can the Earth Have Multiple Moons?
Asteroids are constantly whizzing by the Earth. Every once in a while, one of these asteroids gets close enough to be caught by the Earth’s gravitational pull. The asteroid then gets pulled in to orbit around the planet, and then stays there indefinitely until it’s slung out of orbit and back out into space.
How Come We Only See One Moon?
Now, you’re probably wondering why we only see one moon when we look up at the sky. Well, the asteroids that become satellites circling the globe are too small to see with your naked eye. They also are not illuminated by the Sun’s light like the moon is. Any object passing through space the same size and distance away as the moon would simply whiz eight by our planet; it would be too big and moving too fast for our planet’s gravity to capture it.
How Was Our Original Moon Captured?
So, I just told you that it’s impossible for the Earth to capture a moon the size of the moon we all see in the sky, and that’s probably making you wonder how we caught that moon in the first place. Well, the Earth didn’t catch our moon.
Where Did Our Moon Come From Then?
Scientists believe that during the early formation of Earth another planet-like object collided with Earth, taking out a huge chunk of it and sending tons of debris out into space. Eventually the debris from this collision began to clump together, increase in size, and eventually form it’s own gravity. Over millions of years, the object condensed into a sphere, as did the Earth reform its sphere shape. What we were left with is the Earth we live on today and our moon above.
Sources:
http://www.technologyreview.com/blog/arxiv/27425/
How Did the Moon Form?