I’ve often wondered why the same temperature feels different in water than in air. For example, if you’re walking around outside and the temperature is 70°F, it feels quite comfortable. However, if you dive into a pool with a water temperature of those same 70°F, it will feel tremendously cold. In fact, a water temperature of 50°F can result in death from hypothermia in as little as one hour! Doesn’t seem to make sense.
Except it makes perfect sense, if you know the science. It’s a matter of heat transfer, or the transition of heat (thermal energy) from a hotter object to a cooler object:
As long as the temperature of your body is higher than the temperature of the surrounding medium (air or water, for example), your body will give off heat. As soon as the surrounding temperature becomes higher than that of your body, though, you'll start to absorb heat.
The amount of heat that moves between your body and the surrounding medium and the speed at which it moves, both of which are important to the sensation of warmth or cold that we feel, depends on how good a conductor the medium is. The reason the water feels colder than air is because water is the better conductor of the two. When you hop into that 60-degree pool, heat escapes your body much more easily than it would if you were standing beside the pool in 60-degree air. Because the water takes more heat from your body, and quicker, it feels colder. (Read the full text here.)
So, our bodies are either giving off heat (if the temperature of the surrounding medium is lower than our body temperature) or absorbing heat (if the temperature of the surrounding medium is higher than our body temperature). But that begs a further question: if our body temperature is 98.6°F, why does it feel uncomfortably hot to be in 98.6°F air temperature? You would think that there would be equilibrium between your body and the surrounding medium, resulting in no heat transfer, and total comfort, right? Wrong.
As it turns out, our bodies constantly need to disperse heat, and when the temperature of the surrounding medium is equal to or higher than our body temperature, we are unable to effectively do so, hence we feel hot and uncomfortable. All else being equal, the human body operates most efficiently when the air temperature is about 70°F. Again, it all makes perfect sense, if you know the science.
Things don’t make sense. Until you know the science, and then they do. The question is, how should we handle those things for which the science is beyond our current understanding? Hopefully by working hard on the science. And being patient. No need for irrational constructs. Or fairy tales. Just sayin’.