Narrator: A city in China wants to launch an artificial moon into
orbit by 2020 as a way to reduce energy needs
by replacing street light with artificial moonlight. Regardless of whether or not they succeed, their ambitious idea
really made us wonder. What would happen if Earth had two moons? Well, it wouldn't be pretty. Imagine the moon's identical
twin comes hurtling by and is trapped by Earth's gravity. As it settles into orbit
halfway between Earth and our original moon, it
yanks violently at the oceans. In the real world, this
is how our original moon helps generate tides. So, the second moon
would amplify the effect causing peak tides that
would be six times higher, eroding shorelines and flooding many of our world's greatest
cities including New York, Singapore, and London, gone. But not all destruction
would happen on Earth. The combined pull of the
planet and the original moon would also yank on the second moon. The second moon would be
caught in a tug of war between earth and the original moon. The gravitational pull back
and forth from both ends would warp the second moon's surface triggering tremendous
volcanic activity flooding the second moon's surface
with red hot rivers of lava just like hundreds of the
volcanoes you see today on Jupiter's hellish moon, Io. But even that's not the
end of the spectacle. Right now, our current moon
is spiraling away from Earth at 3.8 centimeters a year. That's about how fast
your fingernails grow. At the same time, it pulls on the Earth slowing down the planet's
rotation which is actually lengthening our days by around one second every 40, 000 years. It may not sound like much,
but with two moons in place, it would accelerate
this process even more. Millions of years from now,
the day will have grown by 16%, lasting longer than 28 hours. Now a little extra time in
the day may sound pretty nice, but here's the problem, the extra moon would drift
towards the current moon and that's where the real danger comes in. After millions of years,
the two moons would collide. The impact would be so massive, it would rip the very
core of the moons apart. Lava would erupt from their center like a runny egg in space
casting a vivid, red light in the sky on Earth. Meanwhile, debris would go
hurtling in all directions where some of it would
inevitably strike Earth forming massive craters miles wide. It would be an apocalypse
for all life on Earth. And what didn't hit the planet
would instead be trapped by Earth's gravity
forming a ring of debris around the equator similar
to the rings around Saturn. But not for long. Within just a few years, those
chunks would clump together forming one, large, single body. Perhaps any life that survived
will call it the moon, or maybe something even better.
