You’re Really Glowing Today

The ‘Trinity’ nuclear detonation test in 1945. Source: United States Department of Energy via Wikipedia Commons.

On July 16th, 1945, The United States of America conducted “Trinity” – the first successful nuclear detonation test. The late physicist Richard Feynman was present and recounted his experience:

“They gave out dark glasses that you could watch it with. Dark glasses! Twenty miles away, you couldn’t see a damn thing through dark glasses. So I figured the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet light. I got behind a truck windshield, because the ultraviolet can’t go through glass, so that would be safe, and so I could see the damn thing.”

It’s unsurprising, yet tragic, that such a weapon releases extreme levels of radiation. Just three weeks later, the atomic bombings of Hiroshima and Nagasaki began, and the resulting radiation took thousands of lives.In such turbulent times (where the threat of nuclear bombs is again making headlines), let us not dwell on this tragedy for it hits a little too close to home. It’s time for some science.

Somewhat like a thermonuclear detonation, everything in the universe emits radiation through a process called Black Body Radiation. In fact, though you can’t feel it, your body is radiating away infrared light at this very moment; which allows infrared cameras to detect humans (and other animals) in the dark.

Human as seen through an Infrared camera. Source: Cody.pope via Wikipedia Commons.

Why does black body radiation occur? To a prison escapee avoiding the police’s night vision cameras, this question is of paramount importance!

The key lies in temperature. According to Wien’s Law (a law of thermal physics): as an object’s temperature increases, the energy of its emitted radiation increases. So, unsurprisingly, the Sun’s radiation has a much higher energy than our body’s. Wien’s Law holds a profound implication: all objects must emit some black body radiation because all objects possess a temperature.

There’s no escaping it, everything in the Universe radiates. From your last taco to a cup of tea, all objects are, in a sense, glowing. So next time you’re alone in the ‘dark’, remember that it’s never truly dark – because your body will always glow with infrared radiation.

Source: “Surely You’re Joking, Mr. Feynman!”