heat by chance

minipost 

We still have a bit of snow on the ground - slushy stuff that is partly translucent.  I tried forming someone of it into a sphere.  With clear enough ice and some polishing with your gloves you can make a spherical lens good enough to start a fire.  (from several years ago)  I didn't get there today, but a neighbor asked what I was doing and how could I stand all of that cold going to my hands.  I said it wasn't bad, but that's not what's going on.  Cold isn't moving from the snow to my hands - rather heat is moving from my hands to the snow.  There was a puzzled look.  

It turns out to be easy to understand what's going on and that discovery was part of a revolution taking place in physics at the end of the 19^th century that led directly to quantum mechanics.   It's not some fundamental law, but rather just chance .. nothing deeper than that.

Boltzman figured it out.  You can think of heat in terms of molecules vibrating in a solid or shooting around in a gas.  The more energy they have, the greater this agitation.  Consider a tank of air with a divider.  Make one side hotter than the other.  It's air molecules are zipping around faster than those on the other side.  Remove the divider and the hot and cold gases mix.  (you could do this with liquids or solids - same idea)

It is more probable that a faster moving molecule collides with a less energetic molecule than the other way around.  In the process it leaves a bit of its energy.  Energy is conserved and given enough of these collisions the extra energy in from the faster molecules tends to get equally distributed and everything eventually comes to the same temperature.

At the time it was crazy to think that something as how heat flows might be governed by chance.  It would take years to understand his result.  In the process a very deep understanding of heat would emerge and prepare people for a radical rethinking of what the microworld was. 

In the meantime enjoy the fact that you're heating up a bit of the cool March air when you go outside.

 

 

 

Comments

[Jheri]

This is so clear. I had been told hot moves to cold, but nene why.