BOB HIRSHON (host):
The temperature of a breeze. I’m Bob Hirshon and this is Science Update.
Most cars now have thermometers that show the temperature outside. Karen McLaughlin wondered whether the thermometer would show a lower temperature when the car’s moving, because of wind chill. We asked spacecraft thermal control engineer Jack Ercol at the Johns Hopkins Applied Physics Lab. His response?
ERCOL (Johns Hopkins Applied Physics Lab):
Well, for a standard mercury thermometer, it will not change. Air temperature is air temperature.
So why does wind feel cooler, and why does blowing on soup cool it down?
The air moving across the bowl of soup is going to transfer more heat, because the convective coefficient is going to be higher in the moving air than it would be in still air.
In other words, moving air carries heat away from a warm object faster than still air, but its temperature is the same. If you have a science question, call us at 1-800-WHY-ISIT or email us from our website: www.scienceupdate.com. I’m Bob Hirshon for AAAS, the science society.