Anyone who enjoys good science fiction has learned to be disappointed at television and movie portrayals of the genre. This is doubly true of hard science fiction stories.
I’m watching Meteor, the two part miniseries that aired on NBC last month. Frankly, it’s laughable.
A comet hits an asteroid and knocks it off course. Now, the 60 mile asteroid is on course for the earth. It’s preceded by seemingly limitless smaller meteors that were blown off the asteroid by the comet collision. These smaller meteors are a problem. They’re moving far too slowly. If you get out to the asteroid belt and throw a rock toward the Earth, it’s going to accelerate the whole way because of the gravitational pull of the sun. It’s as if it is rolling down a steep hill. The typical speed of a comet or meteor reaching the Earth is in the neighbourhood of 10 km/s (6 miles/second), or 36,000 km/h (22,400 mph). Despite this ridiculous speed, members of the armed forces on the roofs of high-rises in downtown Los Angeles with shoulder-mounted surface-to-air missiles, shooting down the meteors.
But let’s let this pass and ignore the speed problem. If you blow up a rock with an explosive, what do you have? Many smaller rocks. A few kilograms of explosive won’t vapourize a rock the size of a car, it’ll just knocks a few pieces off, or perhaps cause it to break up. There’s still no change in mass and therefore, no change in kinetic energy. It’s still going to make a hell of a wallop when it hits the ground. In a best case scenario it might be the equivalent of trading the sensation of being shot will a bullet to being hit with a shotgun blast. The impact is spread out a bit, but it’s still going to make an awful mess.
Then the big one comes, though we later learn it’s only half of the asteroid. But still, it’s half of a 100 km (60 mile) ball of rock. The satellites are out so they wait until it reaches the edge of the atmosphere and fire all the nukes at it. They blow it up.
Not so fast, there. Nuclear detonations are incredibly destructive to people and their fragile constructions, but they don’t create large geographic changes. Even worse, nuclear explosions aren’t nearly as destructive in a vacuum. There’s no shock-wave because there’s no medium to carry it. The thermal pulse isn’t threatening to rock, either. The entire arsenal of the Earth would do nothing but shave off a bit of the outer surface of an asteroid so large, perhaps breaking some more pieces off. But even of it did break it up, we’re left with the same problem as those shoulder-mounted weapons. The main mass of rock remains, and it still hits the Earth.
Not that anyone nearby would know it. Have you ever used a bicycle pump? The valve gets extremely hot because compressing a gas creates heat. Small meteors that we see as shooting stars burn up in the mesophere, which is between 50 km and 85 km above the Earth’s surface. Now imagine a meteor 100 km across entering the mesosphere and hitting the Earth’s surface eight seconds later. There’s no time for the air to pushed out of the way. Instead it gets pushed down, under the meteor, and compressed. The cylinder of air 100 km across and 50 km high is compressed, and compressed, and compressed. It gets hotter and hotter, and before the meteor strikes the ground, the temperature of the air will exceed the temperature at which foliage, people, and building materials will burn. If anyone manages to survive for more than a few seconds, they’ll be put out of their misery very quickly when the meteor turns into a meteorite.
Depending on the meteorite’s size, a large portion of the Earth’s surface around the impact will flash into flame. And by a large portion, I mean most of the side of the Earth on the same side as the impact. A strike that size in the United States would incinerate North America. The forests would be gone and any hint of global warming would be erased by the soot in the air and the re-awakened volcanoes. The nuclear winter discussed during the cold war would be a cool day at the beach compared to this. There would be no hint of sunlight for months. An ice age could be triggered. The climate wouldn’t return to anything we’d recognize as remotely normal for centuries if not millennia. They call this an extinction-level event because months of darkness would have plants die on land and plankton die in the sea. They’re the foundation of life and each successive level of organism would die as the creatures and plants they depend on die.
It wouldn’t mean the end of life on earth, but it would certainly be the end of homo-sapiens as a species. The impact that scientists believe extinguished the dinosaurs was an asteroid over 10 km in diameter. And the writers of this miniseries expect us to believe that we can deal so effectively with a 100 km asteroid?
As is often the case with hard science fiction movies, the truth of the matter far outstrips the writers’ imaginations.