I recently got this comment of incredulity on my article about what wiped out the dinosaurs?
I´m sorry. But i don´t believe this. In my opinion they were wiped out by a climatic changing.
And I think it’s worth — with the help of a little math and physics — looking at what this asteroid impact might have done.
First off, we need to know how massive this asteroid was. This asteroid was about 10 to 12 km in diameter, which is large, but less than 0.2% the diameter of the Earth. It’s pretty unremarkable, and makes it a pretty typical minor asteroid. For comparison, this makes it about half the size of the known asteroid Gaspra, shown below.
What we’re going to do is figure out the mass of our asteroid, calculate how much energy it hit the Earth with, and see whether that would be enough to have an appreciable effect on the entire planet.
Mass first. For a sphere that’s 10 km in diameter, let’s assume it’s got the same density as typical rocks on the Earth’s surface; about 3 grams per cubic centimeter. I get that this asteroid was about 1.6 x 10^15 kg in mass. That’s a big number, but it’s significantly smaller and lower in mass than, say, Mount Everest.
The thing that makes this asteroid so vicious, though, is that it had so much kinetic energy when it hit the planet! There are many ways to figure out just how much, but one of the easiest involves a neat physics trick. This asteroid started somewhere out around Jupiter, and fell in towards the Sun. It was only coincidence that it ran into the Earth (that’s what we get for being in the way).
The great trick here is realizing that the asteroid gets pulled in by the Sun, and that — by the law of conservation of energy — the gravitational potential energy that it loses is going to equal the kinetic energy of the rock when it strikes us!
Joules, Ethan? Nobody uses Joules. When we talk about large amounts of energy, we use Megatons!
This means that this “minor” asteroid, impacting with the Earth, released as much energy as 5 billion of the most powerful nuclear bombs ever built going off all at once.
And that is why it’s so hard to believe that — with this much energy released in an impact — this wouldn’t have directly caused a mass extinction. The conservation of energy doesn’t lie.