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.