We believe it was Carl Sagan who said, "Every atom in your asshole was forged in the heart of a dying star." It's another way of saying that the life of the universe is one long story of things exploding and then re-forming into other things, only to explode later and have it all happen again.
So while we spend our lives worrying about some sort of Earth-shaking cataclysm like an asteroid strike or an earthquake, the truth is that we wouldn't be here without disasters even bigger than that. Life as we know it was only able to form because the universe likes to slap us around every few billion years. It's a form of tough love, we suppose.
For example ...
#5. A Cataclysmic Impact Gave Us the Moon (Which Made Life Possible)
Even tiny meteors can make for some spectacular videos, and it doesn't take a very big one to wreck the Earth. So when you imagine an entire other planet slamming into us, well, you've got a disaster scenario they don't even bother making movies about. But it happened, a long time ago.
About 40 million years after the sun was born, the inner solar system became the scene of a turf war between giant piles of rocks. Just as baby Earth was figuring out how to poop in a toilet, a planetoid five times the size of fucking Mars slammed straight into us. That runaway planet even had a name -- Theia.
University of Copenhagen via Spacefellowship.com
And it was a dick.
Once Theia hit the Earth, the shit hit the fan. The planet's iron core smacked us so hard that it eventually melded with our own core. Chunks of both planets catapulted into space. Yeah, Bruce Willis couldn't have saved us from that shit.
Those orbiting chunks of Theia and Earth eventually made sweet love to each other and never got unglued. And that's how we got the moon. Some scientists speculate that it only took a month after the initial impact for the moon to come together. When it's right, it's right, you know?
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You can't see it, but there's a boombox orbiting the moon and blasting Peter Gabriel.
And besides being pretty to look at and the source of our favorite werewolf lore, the moon's large mass is a huge part of why we're here today. For example, without it, we wouldn't have tides. As sea levels change, organisms are exposed to both water and air over a short period of time, forcing them to evolve and adapt. It could have been those changes that gave some animals the push to move from sea to land.
But the moon has another important effect: Its massive size stabilized the rotation speed and tilt of the Earth. Thanks to this, the overall climate of the planet has remained very diverse and incredibly stable over large periods of time, allowing life the necessary time to spread, evolve, and diversify and setting the stage for the rise of mammals and, eventually, us. All because of this random planetary collision that just so happened to create exactly the right chunk of debris.
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Some people make much better neighbors than roommates.
#4. The Iron Catastrophe Gave Us a Core
When scientists talk about the disastrous effects of "global warming," they're referring to a temperature rise of just a few degrees -- that's all it takes to throw everything completely out of whack. Droughts, floods, extreme weather -- all because things are on average just a little warmer than they are now. Yet there was a period in Earth's history when things got hot enough on the surface to melt fucking iron.
And once again, that hell-on-Earth scenario set the stage for people to arrive later.
Australians call this a "hot tub."
You know that the Earth today has layers -- molten core, then rock, then the nice cool surface we live on, with flowing water and green jungles and such. But in the early days, it wasn't like that: It was one big solid mass with elements distributed throughout. After 500 million years, everything started to heat up. Pretty soon the evenly distributed iron and nickel melted and started flowing. As you know, gravity has this adorable way of drawing the heaviest elements toward itself -- it's like the local Walmart in that respect. The heavy stuff sank to the core of the Earth, setting everything else on liquid fire as it moved. For half a billion years, everything -- the surface, the core, the middle bits -- was hot magma. It was kind of like the irritating "lava level" every video game has.
"Jump. Dude, jump. MOTHERFUCKER, JUMP!"
While the heavy elements like iron and nickel were sinking to the core of the Earth, the lighter ones like silicon and oxygen were forced to the surface. Usually we're not fans of segregation based on lightness, but in this case, things kind of worked out for us. Once everything cooled down, we ended up with a nice airy crust, a medium-density mantle, a liquid metal outer core, and a solid, spinning inner core that is as hot as the sun.
So that's one benefit. The other is that this hell of an epoch created a giant spinning ball of iron that generates a powerful magnetic force field around the entire planet. This force field deflects solar winds and all kinds of other space radiation away from the Earth. Without it, our atmosphere would slowly be blown away, turning our environment cold and dead, like Mars.
Look at that asshole. Fuck that place.
All of that changed due to this nightmarish phenomenon scientists awesomely refer to as "the iron catastrophe."
#3. Our Oceans May Be the Result of Massive Comet Strikes
Go outside and look at the moon. Even with the naked eye, on a clear night you can see that it's absolutely covered with craters caused by projectiles that have been punching the shit out of it for millions of years. What you may not realize is that, while our planet has enough tectonic activity to cover up our biggest scars, it has taken just as much abuse. And it's a good thing, too -- the Earth might be completely dry otherwise.
Scientists theorize that the orbits of the planets shifted about 4 billion years ago, creating a gravitational kick that pushed Neptune outward, smashing it into the ring of comets surrounding our solar system. Millions of comets were scattered in all directions, literally bombarding Earth, Mercury, Venus, and Mars nonstop for about 100 million years. They call this the Late Heavy Bombardment, and it was kind of like Deep Impact times a thousand.
Digital Vision./Digital Vision/Getty Images
It's why the scientific community refers to them as "astrenemas."
There's evidence that points to our run-ins with comets and asteroids as a source of water on Earth. Specifically, scientists have discovered a water-carrying comet that originated from the exact same belt that beat the crap out of us 4 billion years ago. Comets are, after all, just dirty snowballs, so the idea is that if your planet gets hit with enough of them, soon it'll be covered in oceans. And by "soon" we mean in tens of millions of years.
But, like everything else in history that we didn't see with our own eyes, not everyone is convinced that the Great Beat-Up Session was how we got water. Even if not, we can still thank the Late Heavy Bombardment for our existence, because Jupiter redeemed itself by becoming our personal bodyguard. After knocking Neptune around, Jupiter took a new position in the middle of our solar system. So for the last few billion years, we've had a big fat gas giant blocking our path from would-be planet killers.