Wednesday, November 17, 2004

What I think about while I lie awake at night, Part I: Is there a physicist in the house?

Last night at about this time (3:00 a.m.) I woke up and couldn't get back to sleep. It happens occasionally that I'll wake up in the middle of the night with a thought or a problem or a question that just won't go away. Usually its work related--a odd insight or a different angle or a new approach to a case I'm working on--but not this time. This time, it had to do with Apollo 13. The movie.

In particular, it was the part of the movie where it gets mighty cold in the space capsule. I don't know why this bothered me or why I thought about it last night. I hadn't seen the movie in years.

But here's the problem. We were all told in school that space is a vacuum, or at least pretty darned close. And we also all know that a thermos gets its insulating power from the double-walled bottle with the air sucked out. And, of course, we were all told in some high school chemistry or physics class that heat is heat is just excited atoms bouncing around spatistically.

Now, when a hot thing comes in contact with a not so hot thing, the excited atoms on the hot object bump into the less excited atoms in the not so hot thing, and some of their excitement is transferred. But some things are less excitable than others and act as insulators. But nothing is less excitable than everything, which is why a vacuum bottle in a thermos is so good at keeping hot stuff hot and cold stuff cold.

Which brings us back to Apollo 13. As it hurtles through space past the dark side of the moon, it gets very cold. But its traveling through what's supposed to be a vacuum. So why doesn't all that space (outside the spaceship) work as a first-rate insulator? Since there's nothing for their ship's excited atoms to bump into, where does all that excitement go? It seems like rather than get cold, they all ought to be cooked by the time the mission is over just from their built up body heat, electrical equipment, rocket engines, and so forth.

But that's not what happened.

So obviously it was just a problem of bad writing. The moon landings never happened. All done on a soundstage somewhere. And the Apollo 13 mishap was just another staged event to make the supposedly successful missions look more credible. But when they wrote the script for Apollo 13, they just figured that space was cold without considering that it's really a giant thermos.

That's my favorite theory. Not because I think it's plausible, but because I like conspiracy theories. Unfortunately, the fact that it gets cold at night (proving to my satisfaction that planets have no trouble giving off heat to supposedly empty space) suggests that the conspiracy theory is not an adequate explanation.

So what is it then? A number of possibilities came to mind.

First, suppose space isn't really a vacuum? I'm not thinking the stray bits of space dust or gas molecules floating around. I'm sure they're there, but I don't see how they could possibly be there in sufficient quantities to absorb the amount of heat necessary even to drain away excess body heat.

But I vaguely recall from the reading comprehension portion of a standardized test I took twenty-five or thirty years ago that it had been postulated that everything moves through the ether--an unknown substance (using the term loosely) that allows things like light and electromagnetic waves to travel through space. I believe it was talking about "ether drag," and experiments done to try to prove its existence. But I also recall from that same reading comprehension test that the "ether drag" theory had been discredited and discarded. But I also seem to recall from an article I glanced at somewhere that ether might be making a comeback in some circles. I dunno. But it was something to think about.

And then there's PV=nRT. Another relic of some high school science class rattling around in my head. "P" is pressure, "V" is volume, "n" has something to do with Avogadro's number--the number of moles of gas in V (I think), "R" is a constant, and "T" is temperature. I keep wanting to call this Boyle's Law, but it isn't. He just said PV=C, where "C" is a constant. I think.

But I really am going somewhere with this.

As anyone who's ever emptied a scuba tank or done whippets (the little cylinders of nitrous oxide, not the dogs) knows, when you release a gas under pressure, it gets cold. I believe it was a man named Carrier who first put this principle to good use and made Southeast Texas almost fit for human habitation.

Suppose the space capsule was leaking. If it were venting gas, that could cool things off. But that doesn't seem to be the case, and it certainly wouldn't explain why it generally gets colder when the sun goes down.

Or maybe its something like evaporative cooling. The way the most excited water molecules turn themselves into vapor and zoom away, taking all that extra excitement with them (not to mention the energy involved in changing states). But that's just dumb. Unless bits of the metal skin of the spaceship were sublimating in pretty prodigious quantities, this isn't a real possibility. Ant thy weren't and it isn't.

But what about light? In any event, light seems to be able to travel through an alleged vacuum and carry with it energy from point A to point B. Of course, a space capsule does not appear to be emitting light, but that shouldn't get in the way. If thermal imagers can take pictures of varying gradations of temperature, something must be going on far outside the visible spectrum.

That was the one I finally went with.

I wonder if they could avoid problems like the Apollo 13 chilliness by wrapping the ship in a reflective film. Maybe one of those Mylar Space Blankets.



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