The first thing I’ve learned about cold today is that it doesn’t exist — it is just the absence of heat. Also, it has to do with kinetic energy and the velocity of molecules, or as Derb might put it, “Kinetic energy = .5(mass)(velocity)^2.” Thanks for all the emails. Here is a quick sampling:

YEAH, RIGHT
E-mail
Subject: A stupid question
The Frost Elf
WHY WE FEEL COLD I
E-mail:
Subject: Heat
Bona fides: MS in Mech Engr Rice University, worked for 2 years in
heat tracing industry (heat pipes in refineries and chemical plants),
NASA research engineer 3 years.
Don’t think in terms of cold, think in terms of heat and a lack of
heat. Heat is a form or energy, and it actually makes molecules expand
or spread apart, because they become more “energetic.”
Heat flows downhill – from a hot object to a cold object. In Iowa, or
in NH, the air lacks heat, and you produce heat. The cold you feel is
the heat energy leaving your body to flow “downhill” to the cold
outside.
WHY WE FEEL COLD II
E-mail:
Subject: What is cold
Temperature is related to molecules whizzing about and banging into each other. As it gets colder, the molecules slow down like traffic near the mall at Christmastime.
Density is the spatial distribution of molecules – how far apart they are. The heat your feel is due to the number and speed of the molecule whacking into you.
NO WAY!
E-mail:
Subject: A Scientifical Explanation of Cold Air
Actually, Timmy, mass becomes denser when it cools, so the molecules would come closer together when the temperature drops. When molecules cool, the kinetic energy drops, and thus the molecules vibrate slower. At absolute zero (the complete absence of heat) the molecules would lose all energy and would fall right to the floor and you’d trip on them. It’s true! Tell any scientist that at your local sciencetorium and he’ll think you’re smart.