13 February 2009

The Moulton Demon

This morning dawned clear and cold. Despite the cold, the snow was fast. But I was not: a good morning for an "easy" (though still highly aerobic) workout, and a lot of thinking. Skiing along, you can feel yourself pass through warmer and cooler regions. This morning, the temperature around The Moulton trails varied from -8 deg F to +10 deg F. Why is that?

The mathematician and theoretical physicist James Clerk Maxwell (1831-79) helped develop a statistical understanding of gas temperature:

When we say, "The air is -10 deg F," we are talking about the average temperature (i.e. kinetic energy) of many, many air molecules. If we plotted out the "temperature" of each individual molecule, the resulting graph would take the form of a Gaussian (aka "normal") distribution:

In the open air, the molecules mix, transfer energy to one another, and the air is a more-or-less even temperature. What would happen, Maxwell wondered, if we could sort the individual molecules. Install a partition, and herd the "hot" (fast) molecules into one side, and the "cold" (slow) molecules into the other side. All that it would take is a tiny being who could recognize each molecule as it came by, and open a little door to let the hot (or cold) ones into the other room. Thus was born Maxwell's Demon, from Universe-Review:

Alas, poor Clerk Maxwell, also known as "the life of the party" anywhere drinks were served, was allowed few such reveries. Mrs. Maxwell was something of a Demon herself (i.e. a Presbyterian) when it came to sorting out the fun in life. As soon as Clerk would get into his third pint and start to unwind, Mrs. Maxwell would say, "Mr. Maxwell, it is time to go home...you are beginning to enjoy yourself."

The old Moulton Dairy meadow is one of the coldest places along the trails. Forget easy explanations such as "cold air settles into low meadows on calm nights," or "Mrs. Maxwell lives here." No, let's go for the paranormal. A Moulton Demon that stands guard around the meadow, herding the hot molecules out and the cold ones in. In fact, THERE IT IS! See that layer of haze at the lower end of the meadow? That's the Demon, here caught on film:

Climbing the trails to Nipper Junction, we leave The Moulton Demon behind. It's warmer up here, as these little demon people that were so active last night know:

Probably the tracks (note the tail drag) of our common deer mouse (Peromyscus maniculatus):

Years ago, while camping in a cave, I first heard the song of the deer mouse. In the powerhouse (the central engine location for pumping rod-activated oilwells), Gramps tamed deer mice so they would come to him and take crumbs from his hand at lunchtime. Hmmm... I'm beginning to enjoy myself...must be time to go home.


The Moulton: Montana's finest cross country ski trails, just five miles north of Butte America.


troutbirder said...

Scary..... but fun!

tsduff said...

That is one cute mouse.

EcoRover said...

The world's a scary place, Troutbirder--especially for those mice traverses broad expanses (20, maybe 30 feet?) of open space at night when the owl and fox people are about...

Mice ARE cute, TSD--I think our affection for the mouse people is probably testament to our evolutionary past--seems I read somewhere that early primates were mouse like?

David Hobbs said...

Of course Maxwell's gedanken experiment assumes thermodynamic equilibrium, i.e. both vessels at the same initial temperature as the great experiment begins, and that the demon actions require no work on the system. The second law deals with isolated systems...so there is the question of how the Demon interacts with the gas and how he/she determines relative gas velocities...which would required measurements or information, both impacting the total energy of the system. So it goes. Fortunately for us...and the Ecorover...very few systems can be described by the Second Law.

Deedee said...

Okay, now my brain hurts, guys. But seriously, Mrs. Maxwell needed to keep a tight reign on old Jim-just look at those pimped out threads he was wearing. :)

CDGardens said...

I like the way you explain trying to divide hot/cold molecules...wish it would work.

That picture you caught of the Demon on Moulton Trail was fantastic...very ethereal;)

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