Ever wonder why your highlighters glow in the dark? How about glow sticks at a rave? Our world is full of glowing objects that awe us even into adulthood, and their existence is easily explained.
Ultraviolet light is a type of electromagnetic radiation, as are radio waves, infrared radiation, X-rays and gamma-rays. UV light, which comes from the sun, is invisible to the human eye. It makes black-light posters glow, and is responsible for summer tans — and sunburns. However, too much exposure to UV radiation is damaging to living tissue.