Sunday, April 4, 2010

Forrays into movie criticism.

Although I neglected to mention it in my last post, I spent part of yesterday evening watching the latest Star Trek movie (mostly because Josh and Jonathan put it on while I was doing homework). I am not a movie critic, so I will not critique the movie (although it had way too much lens flare for my liking), but I am a physicist, so I will critique the physics. And let me tell you, if the level of astrophysical knowledge displayed in the movie was in any way indicative of the general populace's knowledge of the subject, I will suddenly understand where some of the odd questions we get at the Vis now and then come from.
Let's start with the big one: General Relativity. Where is it? I'm not going to critique such things as faster-than-light travel because that's part of the willing suspension of disbelief, and I'm willing accept it. But the black holes were completely unrealistic! In reality, you would never see something fall into a black hole like that. This is because, in GR, curved space time causes time dilation, and infinitely curved space (a.k.a. a singularity) causes infinite time dilation. If you watched something fall into a black hole, you would never see it hit the event horizon and pass beyond -- it would simply become dimmer and redder, forever. In addition, gravitational tidal forces would stretch it into spaghetti long before it reached the event horizon, especially with a small black hole (counter-intuitively, large black hole have small tidal forces and vice-versa).
And all that part about the singularity consuming a planet in a matter of seconds. Come on! If the planet had any amount of rotational motion when it happened (virtually certain), the Conservation of Angular Momentum would spin it up into a rapidly rotating accretion disk which would take a very long time to lose its angular momentum through frictional heating before it could pass beyond the event horizon (admittedly, still not optimal for the inhabitants).
Plus, you have to worry about Hawking radiation. In essence, the intense gravitational energy around a black hole constantly switches between being energy and matter, creating virtual particle/antiparticle pairs in the vicinity of the black hole. If one of the pair happens to fall into the black hole, the other can escape, taking with it a tiny amount of the black hole's mass. Over time (tens of billions of years for a typical few-solar-mass black hole) the black hole would evaporate if it received no additional matter. But the picture is very different for smaller black holes. In fact, if you were to create a black hole with the mass of a massive atom, it would evaporate in such a short time you'd never even know it was there. The Large Hadron Collider may have already created such tiny black holes, and we wouldn't be able to tell (so now you know how to refute those people who think it's going to create a black hole that will engulf the world).
And then there's the whole matter of the supernova engulfing the Romulan planet. Where to begin with that? For a supernova to actually engulf and destroy a planet like that, it would have to be the star that the planet was orbiting in the first place (barring some weird globular cluster configuration, which didn't seem to be the case). And yet they have no idea that the star is going to go supernova? Stars undergo enormous changes in temperature and physical size before the end of their life, changes that make it quite obvious that they're going to blow. We know of several stars in the Milky Way that are candidates for popping off at any time (Betelguese and Eta Carina are two I can think of off the top of my head). Granted that we can't predict exactly when, it certainly doesn't happen overnight. You'd think the Romulans would have evacuated their planet at the first sign of their sun going supernova. There are certainly very real dangers from supernovae, even at great distances, such as gamma ray bursts, but this obviously wasn't such an event.
I should probably stop speaking my mind and picking nits like this, and point you to the Bad Movie Physics entry for the movie, which brought up a bunch of points I hadn't considered. I hope, that if you enjoyed the movie, this doesn't decrease your enjoyment of it. Though the physics may be bad, I find it a subject more for laughter than anything else (and I did break into laughter a few times at odd points).
A hui hou! (until next time)

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