Why do we feel hot in temperatures close to our body temperature?
Our normal body temperature is approximately 37°C. Even so, the outside temperatures close to this value cause a lot of sweating and hot sensations.
The normal core body temperature, also known as normothermia, is 36,8±0,4 °C.
However, the individual body temperature depends on various factors- including gender, age, time of the measurement, health, emotions, physical activity etc. Or, if measured in women, on the menstrual cycle phase.
During the summer period, the thermometer sometimes shows values close or even higher than 37°C. At this time we tend to feel really warm, even though this temperature should, by definition, feel natural to our bodies. What is the reason for that?
Human body is trying to maintain a stable temperature. This is not only a product of our metabolism, but also represents a desirable value, which assures optimal enzymatic activity, maintains our internal organs, or even prevents various fungi from growing.
Physics of body temperature
Thanks to the second law of thermodynamics, the heat can only flow from warmer object toward the cooler one. This is why our bodies lose energy at all times. If, however, the temperature of our environment rises to let´s say 30°C we start to lose our heat much slower.
In order to prevent overheating, our body activates its protective cooling mechanisms. For instance increasing the blood flow in the capillaries close to the surface of the skin intensifies the heat transfer from our blood to air.
This is also the reason, why our face, or even the whole body, turns red while we feel hot (think about the last time you went to a sauna or for a run).
Is the air warmer than water?
You might have already noticed something interesting during the summer months or during holidays by the sea. When we dip into the water, which can have as much as 30°C, it seems much colder than air with the same temperature. Again, it is physics with its second thermodynamic law to blame.
When exposed to increased temperatures, our sweat glands begin to produce sweat, which subsequently evaporates on the surface of the skin.
By this process the skin cools down, which, in return, increases the temperature difference between our skin and its surroundings.
Not to mention direct sunlight with its infrared waves, which are capable of heating up not only our clothes, but also our skin. All these factors contribute to our personal sensations, including feeling hot.
If we however go for a swim in water with similar temperature as air, it can seem far less warm. The reason behind this is a specific property of water called heat (or thermal) capacity.
That, by definition, means that we would need quite a lot of heat to increase its temperature by one single Kelvin. Moreover, the heat transfer is much faster in water compared to air. That means that our skin gets cooled down to the same temperature as water quite fast. Therefore we stop to feel the temperature difference, as it no longer exists.
Original article: https://dennikn.sk/472399/preco-sa-nam-zda-30c-vela-ked-teplota-nasho-tela/
