I don’t know if anyone (other than a few friends) is reading this blog, but if you’re out there, I hope you appreciate the pain and suffering I am going to endure during this next section. Do you know how many movies there are about asteroid/comet impacts? Neither do I, but we’re about to find out.
Let’s start in a happy place: Deep Impact. 1998 was the summer of impact movies. While deeply flawed (I’m sorry) Deep Impact is by far the better of the two. We’ll come to the other one later. After comet Shoemaker-Levy 9 smashed into Jupiter in 1994 and two bright comets were visible over the next couple of years, the random danger posed by impacts was fresh in the public conscience. Why not exploit it?
We begin with half-decent astronomy! Red lights in a dome, astronomer not looking through a large telescope with his eye, actual sky coordinates that are actually the coordinates of the location shown in the sky… then they kill him! Can’t have a pesky scientist weighing the film down.
Right away, we get some vitals on the comet: 7 miles across, 500 billion tons, rotating every 14 hours. As if it weren’t evident already, they talked to some scientists when making this film. Those stats are all very reasonable for a cometary nucleus.
In an attempt to deflect the comet, out come the nukes! A team of astronauts lands on the comet, which has almost no gravity since it’s small. Science works! The warheads are drilled down into the comet. They’re 5 megaton warheads, which is pretty reasonable given their size. Since we have to have drama, one nuke gets jammed 25 feet short of its goal. Is that really going to make that much difference? The composition of any comet is poorly known at best, so to assume we know the composition well enough that 25 feet will make much difference is ridiculous.
Of course there’s a rapidly ticking clock. They can only work while the comet is in the dark because the sunlight causes dangerous outgassing. So… where is the dark coming from? Is the Earth eclipsing it? How far is it from the Earth at this point? Earlier we learned that the comet is moving at 26 miles/sec. How fast would it pass through the Earth’s shadow? Does outgassing start that rapidly if a comet is eclipsed by an object? (Hint: if you take my class next spring, you’ll find out the answers to all these questions.)
Surprise! The nuke didn’t work. Now we have two comets headed for us. Time to hunker in the bunker. Nice to know that, when everyone is seeking shelter, you can still find a taxi in downtown D.C. Ok, ok, I’m not going to start punching non-science plot holes in this thing. Is it time for death yet?
So plan B is to just fire ze missiles at the comets in the hopes that they skip off the atmosphere. Of course that doesn’t work, so the little comet is going to take out the east coast and the biggun will hit Canada, eh. Except no! The astronauts manage to save the day. This time, they nuke the jeepers out of the larger comet fragment and it ends in a harmless fireworks show. Too bad the whole east coast had to bite it. So could we nuke a comet just hours before impact and survive essentially unscathed? I’ll answer this in detail later, but the short answer is no. We’d be dead.
So we wrap up this, the best of the impact movies, with a heavy heart and a queasy stomach as we prepare for the monumental task ahead of us.