Have you ever looked up at the sun and felt dread about the idea of it exploding? Well, the good
news is that you’ll unlikely ever see that happen because something more immediate could be on the
horizon. Keep watching to see why some scientists predict that comets might end the world.
Earth's lifetime is not infinite. The planet will eventually be swallowed up by the Sun millions
of years in the future. But, likely, life on our planet won't make it to that apocalypse.
Many scientists predict the fate of humanity is in the hand of blind objects hurtling through the
cosmos. One such event has already actualized once, and it nearly wiped out life on Earth:
impact from a massive celestial object. Sixty-six million years ago saw the demise
of the dinosaurs, caused by the impact and aftermath of a comet or asteroid smashing
into Earth with an explosive force not seen since. The cataclysm saw three-quarters of
all life on the planet extinguished in one of the largest mass-extinction
events in history. And the terrifying reality is that it could happen again.
It would only take a celestial body a few dozen miles across impacting Earth to cause another mass
extinction. While there have been impacts since that fateful explosion 66 million years ago, none
have come close to replicating the destruction caused by the rock that killed the dinosaurs.
Something important to keep in mind about celestial objects is that comets and
asteroids are not the same things. Comets are usually made of ice, rock, and dust.
"Oh, Halley's Comet, of course. The only sufficient source of ice cubes
that don't have bugs in them." Asteroids, on the other hand,
usually contain rocks and metals. Typically, comets come from beyond our solar system,
though many also orbit our sun. They travel at much higher speeds than rogue asteroids as well.
Asteroids on the other hand typically come from the Asteroid Belt located between Mars and
Jupiter. And the difference in their speeds has a huge effect on how devastating an impact can be.
When a large astronomical object strikes, so much dust and debris is launched into the atmosphere
that the sunlight can be blacked out, lowering global temperatures and killing millions of
organisms. The 1908 Tunguska impact — the largest impact event in modern history — thankfully struck
an isolated Siberian forest. That space rock was roughly 130 feet in diameter, and it flattened
trees in an area the size of London. If it had been a couple hundred feet larger,
entire countries would have been flattened by the shockwave. Scientists are worried about such a
possibility, given that there are no real defenses in place to divert or destroy an asteroid.
The scientific community has conducted tens of thousands of asteroid-impact simulations to
determine how object size and area of impact will affect human casualties. Noting that asteroids big
enough to cause global calamities strike at a rate of about two every 1 million years, researchers
hope to use the data to better understand what would happen in a worst-case scenario.
Perhaps surprisingly, those who die from the direct impact, seismic activity, and ejected
debris would make up only a tiny fraction of total deaths. The biggest killer? Wind.
Wind is so dangerous because an astronomical object could explode in the air before it reaches
the ground. If such an explosion occurred over water, there would be tsunamis and shockwaves
that would wipe out a whole lot of costal cities. While an apocalypse-threatening asteroid is highly
unlikely to strike within any of our lifetimes, an Eiffel-Tower-sized rock is going to just miss
Earth in 2029 and 2036. An impact is much less likely than initially feared, but it inspired
MIT researchers to look into the best ways to defend against asteroid impacts. The process
would depend a lot on the asteroid's speed, mass, and whether it has crossed the "gravitational
keyhole" to put it on track to collide with Earth's surface. This keyhole is a very narrow
region of space. If an object passes through it, the gravitational field of the larger body
would put the smaller rock on a collision course the next time the objects’ orbits crossed paths.
Early suggestions included attacking an asteroid with a nuclear bomb, or a rocket strike that would
veer it off course. Other scientists are focusing on methods to deflect asteroids before they cross
the keyhole at all. This would include sending "scout" drones to get accurate measurements of
an astronomical object and slightly nudge it off course. Then the scout would hit it with
another strike just before it enters the keyhole. The exact course of action that would be taken,
should something extinction-level come our way, is yet to be fully confirmed,
but perhaps one day, humanity will need to come together to save ourselves from planetary doom.
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