Remember last month when Bill O'Reilly tried to prove the existence of God by pointing to the rising and falling of the tides? “Tide goes in, tide goes out. ... You can't explain that.”
Unfortunately for O'Reilly, you can explain that -- the tides are caused by the moon's gravitational effect and the earth's rotation. In fairness to O'Reilly, this has only been known for about 300 years and was first explained by that otherwise disreputable quack, Isaac Newton.
But long-established scientific explanations for observed physical phenomena are not enough to deter O'Reilly, and he has responded to all those science-familiar “pinheads” out there with a simple question: “How'd the moon get there?”
How did the moon get there? I mean, this is a moon we're talking about. One doesn't just hang moons in the sky like a loofah on a showerhead.
Many theories have been posited, including O'Reilly's “It was God, so shut up” hypothesis. The theory that most astrophysicists and other “pinheads” of their stripe adhere to is the so-called “giant impact,” in which a celestial body roughly half the size of earth collided with our planet some 50 million years after it first formed. The impact kicked up unheard of amounts of debris, which accreted into what today we know as the moon. The theory isn't perfectly formed yet, but it does help to explain why moon rocks have similar chemical compositions to terrestrial rocks.
So yeah, O'Reilly's follow-up is a little more difficult to answer than his original query on the tides, but no more disqualifying of natural explanations for the physical world.
But he wasn't done quite yet!
“How come we have that, and Mars doesn't have it? Venus doesn't have it?”
Are we still talking about moons? Because if we are, O'Reilly will be disappointed to know that Mars has not one, but two moons, named Phobos and Deimos, the Latin names for two Greek gods.
While I'm tempted simply to mock O'Reilly's almost purposeful ignorance, I will point out that he's right that Venus has no moons. And given his track record, half-right ain't half bad.