I was watching a tv show about ghost hunting on the Sci Fi channel last night when something occurred to me.

But, before I get to what it was, I should preface. I don't believe in the supernatural. Ghosts of dead people, demons, magic, all that superstitious claptrap is complete and utter hooey, as far as I'm concerned. However, I do like to watch these "investigating the supernatural" shows. If it's got psychics or aliens or haunted houses, I'm there. Especially in October.

(Second aside: I'm not sure how aliens became intermingled with the rest of these topics. I suppose it has to do with the fact that they all involve numerous eyewitness accounts and little if any other independently verifiable evidence. Digression ends.)

The reason I don't believe in the supernatural is very simple: if there is something going on, it's happenning inside the universe. That makes it part of nature by definition, even if it is some obscure corner of it. Which means it has to conform to the laws of physics. Maybe not physics as we currently understand it, but whatever the rules really are apply to everything.

That said, on this show they were investigating a haunted inn from the colonial period when they ran into a cold spot. For those who don't know, ghosts supposedly draw energy from whatever's around them, be it charge from a battery or heat from the air. When heat gets pulled from the air it leaves a cold spot. This temperature change can not only be felt by human witnesses but measured by appropriate instruments. I'm talking about a temperature change of up to 20 degrees Fahrenheit, if I understand correctly.

It was the thermometric measurement that got me thinking. The first rule of thermodynamics states that energy can neither be created nor destroyed. It can only change form. If there is a measurable change in temperature of a volume of air, it must be true that a certain amount of heat has been removed from that volume, proportional to the temperature difference. So, if the heat has been removed, it has to have gone somewhere. It can't have vanished from the universe.

Some people might think that maybe the heat spontaneously migrated out of that volume of air and dispersed itself into the surrounding air. One, no one ever mentions detecting a corresponding warm spot. Two, the rules of heat transfer tell us that energy always moves in such a way as to eliminate gradients, not create them. From warm to cool until both become the same. Meaning, blocks of air don't spontaneously discharge their heat. Something has to cause it.

(By the way, I'm being lax in my use of the term "heat." Technically, heat is energy in motion. A volume of mass doesn't contain heat; it contains energy. Put it next to a colder mass, and heat will move from the warmer body to the colder, at which point it becomes energy again. That's a level of vocabulary precision unnecessary to this discussion, so I'm not worrying too much about it.)

Okay, the three methods of heat transfer are conduction, convection, and radiation. The cold spots shown on the show were in still air, so convection cannot be the mechanism. Radiation occurs on a scale that gets swamped by the other two under common conditions. That leaves conduction as the only reasonable heat transfer mechanism. Conduction requires two objects to be in physical contact, with heat moving from the warmer object to the cooler. So, if there's a cold spot, it has to be because there's something even colder in direct contact with the air. And yet there is nothing visible or palpable in evidence.

So, what we're left with is a volume of still air under everyday conditions, with no obvious physical means of heat transfer, getting cold for no good reason. The energy cannot be leaving the universe, for the simple reason that if energy could leave, it would, and that would be detectable using modern scientific methods. If you burn a given mass of a given combustible material, you get a particular amount of energy out, which varies only according to the conditions of combustion. The energy leaving a system must equal the difference between the energy entering the system and the change in internal energy. If the universe were leaking, we'd know it by now.

I did some math. To cool one cubic foot of air twenty degrees F at standard air pressure, you need to remove a certain amount of energy, delta-Q. I'll do the math in metric because that's what all the data I just looked up on the internet were in.

delta-Q = mass x specific heat x delta-T.

mass = density x volume

delta-Q = 1.29 kg/m^3 x 0.0283 m^3 x 1.05 kJ/kgK x 11.1 deg C

delta-Q = 0.425 kJ

Fiddling with the units, that gives us 313 ft-lb, or the amount of energy required to move a 313 lb object one foot. Not a huge amount, but not negligible either.

For the moment, let's assume there's a ghost. It absorbs heat from the air, pulling it into whatever plane of existence the ghost occupies. Since the mundane universe isn't cooling from the cumulative effects of 12 to 18 billion years' worth of ghosts draining heat from our reality, whatever energy the ghosts are stealing must be coming back somehow. Which leads to another interesting aspect: magnetic fields.

Supposedly, the presence of a ghost can be detected by fluctuations in the local magnetic field. Assuming ghosts don't contain any sort of permanent magnets, they must be generating this magnetic field. Perhaps that is the cycle: absorb heat, a miracle occurs, release eletromagnetic waves. If that is so, then the energy in these fluctuations must equal the energy absorbed from the air.

Ah, but there's a problem, isn't there? Any energy cycle that does any amount of useful work will release less energy than it takes in, the difference being the amount of work done. Whatever process the pilfered ambient heat is powering for the ghost will use up some of that energy. So, it won't all come back as magnetic field energy. And we're back to the universe leaking again.

I'd like to get some data on these magnetic fields, so I could do the math and see how the energy equations work out. Because, really, there's no other way thermodynamics could allow something like ghosts to happen.

(P.S.: I recognize that I'm making assumption that ghosts exist on some other plane of existence than the one we're all used to. But that's fairly standard in the ghost mythos, so I don't feel bad doing it.)