12 Things That Really Glow in the Dark

The objects, chemicals, and products listed below are all known to emit light via phosphorescence. They are some of the most famous things that glow in the dark.

Fireflies

Fireflies glow to attract mates and also so that predators learn to associate the light with a nasty-tasting meal. The glow is caused by the chemical reaction between luciferin, a compound produced in the tail of the insect, and oxygen from the air.

Radium

This is a glowing radium painted dial from the 1950s.
This is a glowing radium painted dial from the 1950s. Arma95, Creative Commons License

Radium is a radioactive element that emits a pale blue color as it decays. However, it is best known for its use in self-luminous paints, which tend to be green. The radium itself doesn't emit green light, but the decay of the radium provides the energy to light the phosphor used in the paint.

Plutonium

Plutonium pellet glowing by its own radioactivity.
Plutonium pellet glowing by its own radioactivity. Scientifica / Getty Images

Not all radioactive elements glow, but plutonium does. The element reacts with oxygen in the air, causing it to glow a deep red like a burning ember. Plutonium doesn't glow because of the radiation it gives off, but because the metal essentially burns in the air. It's called being pyrophoric.

Glowsticks

Glow sticks are a glow party staple. You can wear them, hang them, swing them, and wrap them around glasses.
Glow sticks are a glow party staple. You can wear them, hang them, swing them, and wrap them around glasses. Science Photo Library, Getty Images

Glowsticks or lightsticks emit light as a result of a chemical reaction or chemiluminescence. Generally, this is a two-part reaction in which energy is evolved and then used to excite a colored fluorescent dye.

Jellyfish

This glowing jellyfish is the moon jelly.
This glowing jellyfish is the moon jelly, Aurelia aurita. Proteins in many jellyfish fluoresce or appear to glow when exposed to ultraviolet light. Hans Hillewaert

Jellyfish and related species often exhibit bioluminescence. Also, some species contain fluorescent proteins, causing them to glow when exposed to ultraviolet light.

Foxfire

This fungus is displaying the type of bioluminescence known as foxfire.
This fungus, the saprobe Panellus Stipticus, is displaying the type of bioluminescence known as foxfire. Foxfire is a natural form of phosphorescence. Ylem, public domain

Foxfire is a type of bioluminescence exhibited by some fungi. Foxfire most often glows green, but a rare red light occurs in some species.

Phosphorus

Phosphorus glows because of a chemical reaction with oxygen.
Phosphorus glows because of a chemical reaction with oxygen. Admir Dervisevic / EyeEm / Getty Images

Phosphorus, like plutonium, glows because it is reacting with oxygen in the air. Phosphors and phosphorus glow an eerie green color. Although the element glows, phosphorus is not radioactive.

Tonic Water

The quinine in tonic water fluoresces bright blue.
The quinine in tonic water fluoresces bright blue. Science Photo Library / Getty Images

Both regular and diet tonic water contain a chemical called quinine which glows bright blue when exposed to black or ultraviolet light.

Glowing Paper

Bleaching agents in paper cause it to glow under invisible light.
Bleaching agents in paper cause it to glow under invisible light. MirageC / Getty Images

Whitening agents are added to bleached paper to make it appear brighter. While you don't ordinarily see the whiteners, they cause white paper to appear blue under ultraviolet light.

Some papers are marked with fluorescent dyes that only appear under certain lighting. Bank notes are a good example. Try looking at one under a fluorescent light or a black light to reveal additional information.

Tritium

The tritium sights of this handgun glow in the dark.
The tritium sights of this handgun glow in the dark. Pozland Photography Tokyo / Getty Images

Tritium is an isotope of the element hydrogen that emits a greenish light. You'll find tritium in some self-luminous paints and gun sights.

Radon

Radon glows red when it's cooled.
Radon glows red when it's cooled. Tetra Images / Getty Images

Radon is a colorless gas at ordinary room temperatures, but it becomes phosphorescent as it is cooled. Radon glows yellow at its freezing point, deepening toward orange-red as the temperature is lowered even further.

Fluorescent Coral

Many types of coral are fluorescent.
Many types of coral are fluorescent. Borut Furlan, Getty Images

Coral is a type of animal related to jellyfish. Like jellyfish, many forms of coral either glow on their own or when exposed to ultraviolet light. Green is the most common glow-in-the-dark color, but red, orange, and other colors are also known to occur.