Have you ever wondered just how bad the devastation would be if the Moon (or a Moon-sized object) were to graze the Earth? How big the crater would be, how tall the tsunami if it hit the ocean, how far from the impact point you’d have to be to avoid being instantly ejected into space by the impact, whether it would cause the Earth to crack open, that sort of thing? I have, and I’ve been fascinated by these kinds of questions since I was a kid and first learned about asteroid impacts and I read “Lucifer’s Hammer” by Larry Niven and Jerry Pournelle.
If you’re weird like me and enjoy celestial collision end-of-the-world fiction, have I got a site for you. Purdue University and the Imperial College of London have teamed up to create Impact: Earth!, a site where you get to adjust the size, composition of a hypothetical asteroid, comet, or planetoid, smack it into the Earth at a selectable velocity and impact angle, and choose what kind of surface it hits, including the ocean. And after you’ve selected these parameters and chosen where you’re going to watch the impact from (distance from impact), it runs a simulation to determine just what the effects are when they reach you.
I think being able to click on two points on a Google Map to select impact point and your location would be even cooler, but that’s just me.
I ran a couple of simulations with this, and they were fascinating. Did you know that if you rammed the Moon into the Earth and were only 1000 km away from the impact site, you’d be tossed into space by the impact but, at a speed of only 11 km/s, there would be no thermal pulse? I didn’t either. I did, however, guess that slamming a sperm whale-sized (what, no humpback whale or potted petunia?) piece of iron into the atmosphere over the ocean at 72 km/s would produce nothing more than a scattered debris field and no tsunami – the asteroid would be just too small to reach the surface intact.