Mad About Science: Fire

By Brenden Bobby
Reader Columnist

Can you believe I’ve never done an article on fire?

Surprisingly, fire and rust are similar chemical processes. They are both the product of oxidation, the changing of state when atoms or ions come into contact with oxygen and a catalyst. In the case of rust (iron oxide), water facilitates the slow and gradual change from iron to a gnarled, rusted state.

Firefighters in silhouette on the Castle Rock Fire, Idaho, 2007. Photo by Kari Greer.

In the case of fire, the oxidation is extremely rapid and violent.

Fire is hot because the conversion from O2 to CO2 produces energy, and with enough fuel (generally carbon-based, such as wood, paper, petroleum and other ethanol-based accelerants) and oxygen, it can produce a lot of energy very quickly. The flames themselves are pretty awesome when you really think about it. Flames are the light (visible and infrared) given off by the gases heating and changing state. You’re literally watching gas.

The control of fire is, like the wheel, considered to be one of our earliest and most notable benchmarks as a sentient species. However, there is no scientific consensus as to when this happened, and in fact the “control” of fire seems to have been a process that may have happened on and off for over 200,000 years. We used the heat to cook our meat and morph our tools, we used the light to see in the dark and ward off predators, we’ve used it as a weapon against rivals and much more. Our mastery of fire has exploded in the past few centuries, but it’s still not a force that’s completely within our control.

Wildfires are a natural part of how our world works, just like disease. When a forest gets to be overpopulated, lightning will naturally cause a conflagration at one point or another and bring much of the forest into a state of ruin, sending fertile nitrogen into the sky to be cycled down elsewhere while new life gets a chance to develop in the remains of the burned-out forest. However, as anyone from the West Coast is aware, wildfires become terrifying and destructive when we’ve built our homes in the overcrowded forest.

As this year has shown us, we can pretend to be the masters of fire all we like, but with enough moving air and enough fuel, all we can do is try to minimize the damage it does.

One of the coolest things about fire is how it acts in microgravity.

Now, keep in mind, our experiments in microgravity are VERY controlled. You’re playing with fire in a multi-billion dollar pressurized tube that is filled with oxygen just waiting to get its Human Torch on. The potential for catastrophe is huge… but it’s something that’s definitely worth exploring.

We talked about how the flame is the visible light from the changing gas. Where on Earth, you can see the gas moving, dancing around in a distinct shape. In microgravity, the gas isn’t rising above heavier gases, it’s just sitting there in a perfect sphere. It looks really cool.

Seriously, look up “fire in space.”

When talking about fire in space, it’s worth bringing up a more detailed explanation of something we’d talked about recently in our Hollywood Science Fails series. Nuclear explosions in space.

On Earth, if you detonate a nuclear warhead, the fireball is the rapid oxidation occurring in our atmosphere. In space, there’s not enough oxygen to create a fireball, so it would just be a big, bright, spherical flash and sudden bombardment of radioactive particles.

Pieces of debris flung out from the center of the blast make channels and filaments in the blast, so it’s not perfectly uniform, but still looks really cool. The radiation involved can also wreak havoc on our electronic systems and create fantastic auroras. This is called HANE, for High-Altitude Nuclear Explosion, and it produces an Electromagnetic Pulse or EMP.

But Brenden, if fire doesn’t burn in space, what about the sun? Isn’t it a giant ball of fire? You can see huge flames dancing on the surface!

Well, yes and no. The sun is basically a superheated ball of hydrogen gas. Because of its immense size and density, it has a ludicrous gravitational field, and “flames” on its surface would be subject to the ebb and flow of gravity. Its immense size and pressure is what creates the heat, not the presence of oxygen.

Those huge dancing flames you see are actually called corona, and are strands of plasma being manipulated by insane amounts of energy and gravity. They’re basically like giant superheated rubber bands, and when they’re pulled too tight … snap!

As anyone that’s ever been hit with a rubber band knows, that energy doesn’t just dissipate. It fires outward many widths of the rubber band. On the sun, this is called a Coronal Mass Ejection.

Certain chemical fires can burn without oxygen, using other chemicals as a catalyst and fuel source. This is one of the reasons that we have different types of fire extinguishers. Removing oxygen doesn’t help if the fire isn’t using oxygen to burn. Believe it or not, pool chemicals are ridiculously dangerous if not properly maintained. When buying and storing pool chemicals, read the instructions. Seriously.

Next time you’re tossing a log into the fireplace or roasting marshmallows, just marvel at how incredible science is.

You’re warming your house and filling your belly by making wood rust! Dracarys!