How Do Things Glow In The Dark?

The lightning bug, more commonly known as the firefly, is a fascinating creature for everyone. It is probably the only bug that glows in the dark. Have you ever wondered why do they glow? It is because of their bioluminescent characteristic. Fireflies have a natural chemical content, in simpler words, which makes these bugs light up. Fireflies are not alone in this. Animals such as anglerfish, glowworms, and jellyfish also depict this trait. They glow for attracting mates, for protection, and camouflage.

It is not just animals that glow in the dark. We have all heard of glow sticks- famous at nighttime activities in summers, such as campfires and festivals. Glow sticks come with chemiluminescence in them, which makes them glow due to a chemical reaction. Other objects such as a wristwatch, have radioluminescence. It means they have a radium-like element that emits light. Radioluminescent things also glow in the dark. 

Glow-in-the-dark toys such as stick-on stars, yo-yos, and stickers contain phosphorescence. It means they come with phosphors, the unique substances that emit visible light when energized. It means they soak up light all day or for some time before they can glow in the dark by giving off the same light.

Glow-in-the-dark toys can transform any dull room into a fascinating world of adventure in the dark. At times, these objects will glow very weakly, and that too for a short period of time. You will have to put them in a too dark place, and only then you'd see them glowing faintly. The newer toys often have a brighter green glow, which lasts up to several hours. 

To create these glow-in-the-dark objects, manufacturers choose phosphors that can glow for a really long time. After selecting the phosphors, they mix them with plastic and then mold them to the desired shapes. These glow-in-the-dark toys attract people of all ages. After all, who doesn't love shaking a glow stick or chasing a firefly?

We have all seen fireflies glowing in fields and woods during the monsoon and warm months of the year. They are not the only creatures who look like they carry torches around. Depending on the various species, animals use the glow to ward off other creatures, attract prey, scare away predators, and even communicate with one another.

New Zealand is home to certain caves that have a unique species of insects. These hang from the cave ceilings and look like someone has stuck a string of fairy lights or twinkling stars. These insects are actually the larvae that grow into winged insects. In their larva stage, the small glowworms dangle on threads that glow in the dark. These threads are similar to spider webs but are sticky and catch small bugs that get attracted to the light.

Toyama Prefecture, situated in Japan is among the few places where you can find a firefly squid. It is a glittering blue-colored squid that visits the waters near Japan every year. It comes in millions. Firefly squid is tiny- merely seven centimeters in height and together they look like a blanket of stars. The squids generally inhabit the deep underwaters, but during spring, they move near the surface for spawning. A firefly squid has tentacles and little glowing spots all across its body. The glow they emit is dim on its own, but when millions of squids come together, they make the shore shine with its gleaming blue light.

The crystal jellyfish are delicate-looking creatures that thrive in the waters of the coasts of British Columbia till California. It has a clear body and usually stays transparent when it is not disturbed. Once disturbed, the edges of these crystal jellies start giving off a greenish-blue light. These creatures are not only beautiful to look at but have significance in science. Researches have succeeded in taking the protein which makes the crystal jellyfish glow and they use it on other creature for studying and tracking genes. (See Why do some people love rainy and dark weather?)

Anglerfish are considered one of the ugliest underwater creatures. These toothy fish usually prefer to live in the deepest and dark parts of the Antarctic and Atlantic Oceans. These fish use the deficiency of light to their benefit- they have long dorsal fins that act like fishing rods with glowing ends as bait. Other fish get attracted by the light and move closer to the anglerfish's huge mouth. Anglerfish can gobble down fish that are twice their size, so preying on any fish isn't a big deal for them.