The Science of Fiction Q&A

Firebreath for Caid11

Question: how can a dragon breath fire? If no living organism can make fire other than a human, how is it possible?

There are two ways people usually imagine dragons breathing fire, and both are possible in a living organism even if none exist that do it.

1: Sparks and Farts

The first possibility is that the dragon is expelling a flammable gas or liquid. As far as gas goes, lots of animals do that.

Methane, the main component of farts is also part of cow burps. It's a natural byproduct of digestion and also quite flammable. It's easy to imagine a creature that could produce an unusual ammount of methane and hold onto it to use later rather than just expelling it right away.

Being a gas, it takes up a lot of space. Storing enough methane to effectively cook anything requires either a lot of space, or very high pressure. So either your dragon would be a huge baloon, or have something like a propane tank inside of them. Neither seem very practical, but they're possible.

Another posibility is that they produce a flammable liquid. Again, that happens in nature, just not for fire-breathing purposes. Fermenting plant matter creates alcohol. It's difficult to refine the alcohol into a pure enough form to be flammable, but not impossible. There are stranger things in nature.

A challenge with both of these options is actually lighting the gas or liquid on fire. We need a spark. There aren't any examples of animals that create actual sparks, but there are some that show how it could happen.

Pistol shrimp (Alpheidae) have a claw that can snap shut at incredible speeds. They don't make sparks, but they certainly could if they were made out of a materal that could spark, like iron or flint. But that doesn't happen naturally does it?

Turns out it does. 

There's a kind of scaly footed snail that lives near volcanic vents at the bottom of the ocean which incorporates a lot of iron into its shell. 

These animals let us imagine a possible creature who has teeth that could spark if rubbed against each other correctly, and a jaw that could snap hard enough to do it. Unlikely, but possible.

2: Beetle Butts

The second option takes less imagination because it already exists in nature, just at the wrong end of the animal.

Bombadier beetles produce two different chemicals which they store in separate resevoirs in their abdomen. When they combine, they react. That reaction gets very hot, and also produces a nasty liquid which can damage eyes and lungs. The beetles use this for defense, spraying that hot toxic liquid out of a tube at their back end at predators. Imagine having two extra bladders and if you pee out of both of them at the same time it creates a steaming acid explosion. 

Bugs are weird, okay.

It's easy to imagine a system like that in the dragon's head and neck like venom sacks on cobras. A different set of glands on each side of its head produces a chemical, they spray them out and when they combine, the reaction ignites. 

I hope that helps, sorry for the slow response!