[Sean Moore]

Sean Moore asked the Naked Scientists:

Why does the sun drain us of energy? If we invest so much energy into maintaining our warm temperature, you would think a day in the sun would give our furnace a rest and we would have energy to spare. So is our cooling process THAT energy-intensive, or is something else at play?

What do you think?

[Kryptid]

My guess would be that our bodies try to "tell us" to be less active in high heat in order to keep ourselves from overheating. Our bodies are not perfect converters of chemical energy into kinetic energy; there is a lot of waste heat. Just by walking you generate heat. Therefore, the less you move, the less heat you generate. If you're already heated up from being in the Sun, then vigorous activity could potentially lead to overheating. Even cold-blooded animals can overheat.