New Deep Six Podcast

April 13, 2009 7:44:48 AM PDT
Title: "Origin of the Moon"The origin of the Moon is what we will tackle with this podcast. Where did it come from? Because it wasn't always there. ________________________________________________________________________

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Scientists believe if we didn't have a moon just like the one you see in the sky - sometimes in the day, sometimes at night, sometimes in phases, sometimes full, sometimes darkened - the Earth would be different. So different, we would not be able to inhabit it, or survive as a species.

The Moon keeps us in balance. It is locked in a gravitation dance with its partner, the Earth, and keeps our rotation and orbit stable. That dance causes only one side of the Moon to face us at all times. Pink Floyd sang about the dark side of the moon, but in reality, the dark side is really the side we never see from Earth. Contrary to popular belief, that so-called "dark side" receives just as much sunlight as its so-called "light side."

Part of the reason why it can keep us in balance is because of the Moon's size, relative to Earth. The Moon is pretty big - relatively. Its diameter is one-quarter that of the Earth, and if you placed it in front of the United States, the Moon would cover the Lower 48. Most moons in the solar system don't even compare with the planets they orbit, in terms of size. Pluto's moon is an exception - Charon is half the size of Pluto - but there is great debate that Pluto is even a planet itself. Some think those two are actually a dwarf-planet system. But we are not here to debate the status of what once was indisputably known as the only planet to be discovered by an American.

More on the Moon:

Its size also makes it our great protector. Take a look at all those craters on its surface the next time the Moon is visible in the sky. The Moon acts as a shield at times to the many comets and asteroids that can threaten the Earth. Instead of hitting us, they hit the Moon. And the Moon's gravitational pull can serve to deflect those dangerous flying objects away from our surface.

For just those few reasons, the Moon's presence makes living on our planet so much safer. So, we return to our question: where did it come from?

NASA is using its dual STEREO probes to figure that out. They are entering a region of space near the Earth's orbit, which scientists believe hold the remnants of the planet Theia.

Yes, another planet. There is no smoking gun that says it even existed. But some experts think it did.

The "Theia Hypothesis," as NASA reported in a recent article on its website, is a brainchild of Princeton theorists Edward Belbruno and Richard Gott. And it is cataclysmic. This planet Theia got too close to the Earth some 4.5 billion years ago, and smashed into it. If anyone lived on the Earth back then, they'd be pretty shook up to say the least, and probably killed.

As the theory goes, a big chunk of Theia coalesced into what is now the Moon, and found itself captured within Earth's gravitational grasp. Pieces of the collision were scattered across this region of the solar system - but up to this point, are too small to be detected by our telescopes.

The STEREO probes are looking for these pieces of the Earth-Theia collision. If they find definitive evidence, it would be even further evidence of what is a known fact about the universe we live in: it has been, and always will be, an extremely violent place.