Called the Siple and Passel formula, it studies the rate of heat loss for various combinations of temperature and wind. But the study that led to the index was conducted in 1941 and researchers are now questioning its validity. The U.S. Army forged the Siple and Passel tests in Antarctica as part of research to develop warmer clothing for soldiers. Plastic cylinders filled with water were exposed to the different temperatures and different wind speeds. The researchers measured the time it took for the water to freeze in different conditions and developed their wind chill factor from there.
Modern researchers see many flaws in the old experiment.
It wasn't considering the insulating properties of the can, or considering the way the can freezes. Even if the researchers had taken into consideration the insulating properties of the can, major flaws would still remain in the experiment. The human body certainly has different reactions to a cold wind than a canister of water. When you talk about a plastic container, it has different thermal resistance than human skin. Bluestein believes that Siple and Passel's assumption that human skin has a temperature of 32 degrees Celsius is quite wrong.