## Let’s get relativistic

I’d just like to take a minute to explain why Randall Munroe of XKCD is awesome. Again. You see, XKCD’s latest iteration is a site called What If? which attempts to answer hypothetical questions with physics. For science!

The first question? “What would happen if you tried to hit a baseball pitched at 90% the speed of light?” The sheer immeasurable geekery which ensues is absoluely delightful. While Randall makes it pretty clear that this is his best guess, it all makes perfect sense to me. In fact, it’s pretty much exactly what I’d have said. Most people completely forget that for anything to travel through air at speeds like that would have absolutely catastrophic results.

Here’s an excerpt:

The ball is going so fast that everything else is practically stationary. Even the molecules in the air are stationary. Air molecules vibrate back and forth at a few hundred miles per hour, but the ball is moving through them at 600 million miles per hour. This means that as far as the ball is concerned, they’re just hanging there, frozen.

The ideas of aerodynamics don’t apply here. Normally, air would flow around anything moving through it. But the air molecules in front of this ball don’t have time to be jostled out of the way. The ball smacks into them so hard that the atoms in the air molecules actually fuse with the atoms in the ball’s surface. Each collision releases a burst of gamma rays and scattered particles.

I’m glad I’m not the only one who does stuff like this.

Remember kids, kinetic energy is actually the most lethal thing in the Universe. Any moving object has kinetic energy, and any collision with a moving object will release that kinetic energy. Enough energy means that will cause serious damage. An object travelling at three kilometres per second will do damage equal to its own weight in TNT. The same object travelling at 90% the speed of light will do damage equal to its own weight in antimatter.

Really though, don’t mess with kinetic energy. Or at least don’t release it carelessly.

Molecular astrophysicist, usually found writing frenziedly, staring at the sky, or drinking mojitos.
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### 5 Responses to Let’s get relativistic

1. erinvruss says: