We all love things that glow in the dark. It’s fun to take them out in the sun, charge them up, bring them into a dark room and watch them shine. What makes these items emit light? What about things in nature that do the same thing? Let’s take a closer look at things that glow when the lights go out, and what makes them shine in the dark.
If you’ve ever shot a gun with glow sights, you’ve probably seen tritium. This radioactive isotope of hydrogen emits green phosphors as it decays, glowing on its own in nearly every lighting. You can’t get tritium in the United States, but you can order it from overseas if you want to see this glow-in-the-dark isotope for yourself.
You don’t want to step on a jellyfish if you’re at the beach, but have you ever seen one glow in the dark? One species of jellyfish — Aequorea victoria — glows in the dark thanks to a trait called bioluminescence that enables them to generate natural light. Comb jellies possess the same quality, but their cilia refract the light, allowing them to create a rainbow of colors.
This is one element you’ll want to avoid if you’re trying to investigate things that glow in the dark. Plutonium does glow — when it’s exposed to oxygen, it emits a deep red luminescence — but it’s also highly radioactive. When plutonium comes into contact with oxygen, it burns.
You don’t normally think of snails when you think of glowing nature, but the clusterwink snail, native to Australia, is the exception to the rule. This little invertebrate flashes its shell when it’s threatened or there are predators nearby. It’s able to pulse bioluminescence from a single spot in its body, illuminating the entire shell. This light show is limited to the spectrum the snail produces, though — hitting the shell with a red or blue laser doesn’t have the same effect.
5. Zinc Sulfide
If you had a set of glow-in-the-dark stars on your bedroom ceiling as a child, you’re already familiar with zinc sulfide. Also marketed as glow powder, this element absorbs light — both natural and artificial — and releases it back into the visible spectrum as it loses its charge. Zinc sulfide contains phosphors, which can be charged in a variety of ways, and glows until that charge fades.
Summer nights aren’t complete without seeing fireflies winking from the dark. These warm-weather insects use bioluminescence to attract mates, thanks to a light-producing organ in their bellies. This organ combines oxygen with calcium, adenosine triphosphate and luciferin. When this mixture comes into contact with luciferase — another chemical within the firefly — it creates light.
7. Wint-O-Green Lifesavers
All you need to create light sometimes is a piece of candy. Wintergreen hard candies, like Lifesavers, glow briefly when you crush them between your teeth. This is due to a reaction called triboluminescence, which creates light when mechanical pressure — like from your teeth — breaks the chemical bonds of a crystal. Quartz does the same thing when broken, because of its crystalline structure.
8. Glow Sticks
Who doesn’t love glow sticks? These fun party toys glow for a few hours before they fade, and no amount of freezing them will ever bring back their shine. Traditional glow sticks work because of a chemical reaction. A small pane of glass separates a mixture of water, hydrogen peroxide, luminal and sodium hydroxide from a vial of potassium ferricyanide. When the glow stick is cracked, breaking the glass, the two chemicals mix and the result is a fantastic shine.
We don’t live on Pandora, the alien world that serves as the setting of James Cameron’s movie “Avatar,” but you can get pretty close by walking through the forests of Malaysia. Mycena silvaelucens is a mushroom that grows on the bark of trees and glows at night thanks to its internal bioluminescence. You can walk through the forest in the dark and see hundreds of these little green mushrooms hanging on tree trunks and branches.
Millipedes are creepy enough, but can you imagine a glowing millipede? That’s the last thing we want to think about when it comes to things that glow in the dark. Motyxia is a species of millipede that glows in in the dark — thanks to bioluminescence — whenever it’s threatened. You need to be careful with these little glowing insects, though. Its glow is a warning, and if you don’t back off, they start to secrete cyanide from their pores.
11. Tonic Water
OK, this one might not glow on its own, but when exposed to a blacklight or UV light, it makes for some beautiful drinks. Tonic water contains a chemical called quinine, which gives the beverage its iconic bitter taste. UV lights and blacklights act as a catalyst, exciting the quinine in the tonic water and making it glow a bright blue
Imagine walking down a beach on a moonless night and seeing a swath of glowing blue washing up on the shoreline. This is bioluminescent algae that emit glowing chemicals into the water around it, creating a shimmering blue in the starlight. You can spot these fantastic creatures in Malta, Puerto Rico or even San Diego, California.
13. Vitamin B-12
Vitamin B-12 is a vital part of our diet, but did you know that it glows when exposed to a blacklight. Vitamin A, niacin and riboflavin also glow when exposed to blacklight. If you ever want to mix up a glowing cocktail and can’t stand the bitter taste of tonic water, consider dissolving a couple of B-12 tablets in your simple syrup and hitting it with a blacklight. YouTube channel The King of Random even used this to make glow-in-the-dark cotton candy.
Radium is another radioactive isotope that glows as it decomposes. It used to be used in paints in the 1920s, until doctors figured out that its radiation was making people sick. The men and women who used to paint watch faces with radium would become ill after licking their paintbrushes back to a sharp point while working. As it decomposes, it emits a bright green glow that made it popular for decades.
15. Human Beings
This one might be cheating a little bit because it’s not visible to the naked eye, but the human body glows. We emit low amounts of light throughout the day, which scientists believe may be because of changes in our metabolic rate. This light is far too dim to see without high-tech cameras, but the point still stands — humans glow.
What do you have scattered around your house that glows in the dark? Are there leftover glow sticks from your last party, or a set of stars stuck to your bedroom ceiling? Take a closer look at the everyday and unexpected items around your home and see if you can figure out what makes them shine.