Humans Glow in the Dark, Just Too Faintly to See

You are glowing right now. Not metaphorically, and not with some sort of mystical energy — literally. Your body emits tiny amounts of visible light, photons produced as a byproduct of ordinary cell metabolism. The catch is that this glow is roughly 1,000 times too dim for the human eye to detect, which is why your friends have not brought it up.

Scientists in Japan confirmed this in 2009 using ultra-sensitive cameras in a completely dark room. They photographed volunteers over several days and found that the glow is not even emitted evenly: it peaks in the afternoon, follows a circadian rhythm, and is brightest around the face. So there is a reasonable chance you are at your most radiant at around 3 p.m. specifically.

This is technically distinct from the bioluminescence seen in fireflies or deep-sea creatures, which relies on specific chemical reactions. The human glow is called ultra-weak photon emission — a faint exhaust of light produced as your body does the unglamorous work of converting food into energy. Poetic in theory, completely invisible in practice.

The cameras needed to detect this light are sensitive enough to spot a single candle from 10 miles away. Until one of those cameras becomes a standard bathroom accessory, you will just have to take science's word for it that you are, technically, luminous.