Take all the petty little problems we have on this planet, add them all together, and they're hardly worth noticing in comparison to the Chicken Little Scenario. Which is basically when the sky falls on our heads. Collectively speaking, all of our heads. It is only within the last forty years or so that the threat to all life on Earth posed by asteroid strikes has really come to the attention of scientists and politicians. It was, after all, a giant meteorite that destroyed the dinosaurs 63 million years ago. It left a crater on the Yucatan Peninsula 186 miles in diameter. The Chicxulub meteorite was about 6 miles in diameter. And then there was the one that left an 53-mile wide crater in the bottom of Chesapeake Bay about 35 million years ago, and probably destroyed all life on the North American continent. And the one that exploded over the Great Lakes 12,000 years ago that was responsible for the extinction of the Woolly Mammoth, Saber Tooth cats, and the Clovis Indian culture. But, wait. All that was a long time ago. Let's see what's been happening lately. On Feb, 15, 2013, the asteroid known as 2010 DA14 missed the Earth by the smallest margin on record. A mere 17,200 miles, which is less than the thickness of a coat of paint as astronomical distances go. But hey--not to worry. It was only 150 feet in diameter. What harm could it possibly have done? Well, The Chelyabinsk meteor that didn't miss the Earth on---wait for it!--Feb. 15, 2013, exploded over Russia with 20-30 times the force of the Hiroshima bomb. It was only about 60 feet in diameter. Just a coincidence I'm sure. 2010 DA14 was much larger. And zipped by a whole 16 hours later. Yeah: So that makes for two in one day. But, hey, who's counting? We were lucky the Chelyabinsk meteor was a high airburst. A 0.45 megaton ground strike would have probably started WWIII if it had hit the Kremlin. Or the White House. The problem is, the larger the asteroid, the harder it hits, but there's cube-square relationship involved in that. Double the size and the impact is four times greater. Triple the size, and the impact is nine times greater. Quadruple the size, and the impact is 64 times greater. But the real problem out there, the real threat that could strike at any time isn't really those silly little asteroids. It's comets. In fact, all of the really big asteroid impacts in the Earth's history were actually cometary impacts. It turns out that there are a lot more comets than asteroids, and they run to much larger sizes, as well. To put that in perspective, if all the asteroids were the size of marbles, they'd fill a dump truck. If all the cometary objects were the size of marbles, they'd fill a line of dump trucks parked bumper to bumper 200 miles long. Or look at it another way: if the entire Asteroid belt was the size of a doughnut, the Oort Cloud (which is where comets come from) would fill a sphere a mile in diameter. There are only about 2 million asteroids, but there are hundreds of billions of cometary objects. And it gets worse: Asteroids are reflective and fairly easy to see. Cometary bodies, dropping in from out beyond the orbit of Neptune, are as a black as tar and utterly undetectable until they are very close to Earth. An asteroid may give us a little warning. A comet will not. Shoemaker-Levey, the comet that made a truly spectacular impact on Jupiter, was only a hair over three miles in diameter. The IRAS-Araki-Alcock comet that passed within 2.9 million miles of Earth in 1983 was about 6 miles in diameter. And it wasn't even noticed until it was two weeks away. If it had hit the Earth the impact who have been about the equivalent of a 488,000,000 MegaTon bomb. It would have been right on par with Chicxulub. Only it wouldn't have been the dinosaurs that went extinct this time: it would have been us. Between 2000 AND 2016 there were 26 massive cometary explosions in the earth's atmosphere. Some were larger than Hiroshima. We can prep all we want for Life's Little Problems. But we can't do squat about cometary impacts. Until we get off this planet and colonize another, or develop some very advanced technology, we're all sitting ducks. The IRAS-Araki-Alcock comet will be back in 2026 and 2069. There is 1 chance in 3,030--according to NASA--that it will hit the Earth. I don't now about y'all, but I feel lucky.