NARRATOR: Humans have been mesmerized by the moon
since the dawn of man.
And although many theories have been proposed,
scientists cannot say with absolute
certainty how this celestial object came into being.
When I was a student, nobody really
knew where the moon came from.
But because it's so relatively big, this was a real problem.
And I think that there is a tendency
to think that moons get somehow captured by the parent planets.
If you've got one body here and another body coming along,
it can't just get trapped into orbit like that.
The difficulty there is just basic physics.
So this remained a puzzle until about 20 years ago,
when another theory came along.
And that is that proto-Earth was, very early
on in the history of the solar system,
hit by a Mars-sized body, hit obliquely
that this Mars-sized body plowed into the center of the Earth
and became the Earth's core, and a lot of the outer material
got stripped off by this gargantuan collision
and coalesced to form the moon.
Now, they had to come up with a very bizarre theory for how
the moon came into being because all the conventional theories
don't make any sense.
The best theory of the moon's formation
is phantasmagorically catastrophic collision
of two things, you know, at just the right angle
to form this belt of debris that then formed the moon.
But the moon, its exact size is such that it
gives us total eclipses.
Its disk exactly covers the sun.
And the chances of that occurring
are so literally astronomically small, it's very disturbing.
NARRATOR: The sun's diameter is 400
times greater than the moon.
And coincidentally, the sun also happens to be nearly precisely
400 times further away.
This is the reason that the sun and the moon
appear the same size in the Earth's sky,
and why we on Earth can experience eclipses of the sun.
DAVID CHILDRESS: It's just perfectly in that orbit
to eclipse our sun.
The odds of the moon being in that orbit
accidentally are a zillion to one.
So that right there is evidence that our moon
is in a perfect orbit around our planet that's not accidental.
MIKE BARA: In order to have a solar eclipse,
the moon has to be exactly the size that it is,
which is 2,160 miles.
Not 2,161, not 2,159, but 2,160 miles at its equator.
And there are people out there that actually
think that's a coincidence.
The fact is is that that is by design.
NARRATOR: Throughout our observable galaxy,
this relationship and others have not been duplicated.
Other moons are sizeably smaller by comparison
to their mother planet.
Earth's satellite not only orbits closer than it should
for its size, it is also the only moon
in the solar system that has a near perfect circular orbit.
And no other lunar bodies are known
to have such a stabilizing role as the moon has with the Earth.
WILLIAM HENRY: Recent computer simulations
have shown that, without the moon's presence,
the Earth's axis tilt would be completely
different than it is today.
We might not even have seasons as we know them presently.
Without the seasons, it could be very difficult for life
So the moon is actually performing
an incredible function.
Without it, we might not be here.
ALAN BUTLER: There are so many peculiarities about the way
the moon has affected the Earth that one might be forgiven
for believing that there is intelligence behind it,
that something made it that way.
The moon is so strange, so odd in terms
of what we find elsewhere in the solar system,
and particularly in terms of what it does for the Earth,
having made the Earth into a haven for life,
that one feels obliged to ask the question,
could such things have come about by chance?
Was it placed there deliberately?
Was it engineered, maybe by aliens?
And therefore, is our whole existence a planned event?