What If the Earth Collided With Another Planet?

About 50 billion rogue planets are roaming the Milky Way with no host star to hold on to, some of them three times bigger than the Earth. They don’t give off any light of their own and that makes them difficult to spot.

Last time a stray planetoid the size of Mars smashed into Earth, it scattered our planet’s young crust into space, where gravity glued those particles into what we now call the Moon.

This time, it would be all hellfire and brimstone with no survivors left. And here’s a timeline of how things break down…

FEW WEEKS BEFORE THE COLLISION

An unknown object would appear in the sky. It wouldn’t happen overnight, no. We’d know something bad was coming. We’d see the planet slowly growing bigger until one day it started looking just as big as the Moon.

It would seem as if everything was unfolding in a relatively slow pace, but that’s only because of the huge distances involved. Out there in space, the rogue planet would rush towards us at the speed of 11 km/s (7 mi/s).

So get your affairs in order because you and all of humanity are about to go extinct.

DAYS BEFORE THE COLLISION

When the uninvited space intruder came into the Moon’s orbit, bad things would start to happen. The gravitational pull of the alien planet would make the tides on Earth eight times larger than they are now.

Floods would begin to rampage through the coastline cities. You’d want to get away from any large body of water as far away as possible.

And still, the megatsunamis are yet to come.

28 HOURS BEFORE THE COLLISION

The gravity of both planets pulling themselves towards each other would speed up the process. The incoming planet would hit a speed of 60 km/s (37 mi/s).

Megatsunamis would plot their way across the oceans. With this would come lightning storms, plus hurricanes and tornadoes so large they wouldn’t have a number on the category scale.

If you didn’t book yourself a vacation aboard a spaceship that would take you to outer space, your time on this planet would be running out.

THREE MINUTES BEFORE THE COLLISION

The rogue planet enters the Earth’s atmosphere. Provided you hadn’t already been killed by the lightning, hurricanes, flooding, earthquakes or volcanoes, you’d see the rocky invader completely filling the sky above you.

NANOSECONDS BEFORE THE COLLISION

The atmospheres of both planets would be compressed together and glow brightly. It would get so hot that everything on the side of the Earth about to get hit would instantly vaporize. For the rest of the Earth, the ground would become scorching magma.

UPON IMPACT

The collision would cause friction between the two planets. This would slow down their rotation, if not stop it altogether. Millions of tons of superheated rock would be sending a wall of fire in all directions. The shockwave across the Earth would engulf the planet in under 20 minutes.

While the hellfire would rush across Earth’s surface, the planet’s inner core would be melting it from the inside out. This would have one big outcome – the Earth would collapse in on itself. The end of the era.

AFTERMATH

If you did manage to get away in a spaceship, you’d see the massive remnants of both planets catapulted into different orbits. Some of them would hit other planets. Others would be fired out of the Solar System entirely.

Whatever was left would form a new asteroid belt encircling the Sun. Nothing would tell there was once intelligent life on planet Earth.

But hey, the Earth didn’t come to an end in 2012 when a rogue planet was predicted to smash into us and end civilization as we know it. Neither did we get wiped out in 2003, when a woman who told the world she was communicating with aliens predicted another planetary collision.

You can sleep well knowing that this won’t ever happen… Most likely not.

Subscribe to What-If on Youtube or follow the show on Facebook Watch.