Today I finished reading Physics for Future Presidents by Richard Muller. I found one short section pretty interesting (not that the rest of the book wasn’t interesting) in the discussion of applications of infrared radiation. I have copied it here:

“Humans aren’t the only animals that use IR. Pit vipers and mosquitoes also detect the warmth of IR by special sensors, and they use this signal to help find their prey. Human lips are also sensitive, and we use them to judge the temperature of food when it is close to our mouths. Try the following experiment: close your eyes and put your lips close to those of another person. Notice how easily you can sense the warmth.”

My partner and I tried this out and it definitely works. Give it a shot!