Making Fire with Physics

In celebration of April 20th, I thought I’d show you a method for making fire that’s so neat it will work — without fuel or chemicals — both on Earth (left) and in space (right).

We’re going to do it without a match, without a lighter, and without friction. That’s right, the next time someone needs a light, I’ll show you a way to make one that even beats rubbing two sticks together!

Image credit: Gideon Mendel/CORBIS.

Have you ever read the book Fahrenheit 451? The title refers to the temperature — 451 degrees Fahrenheit (233 Celsius) — at which paper will spontaneously, in the presence of oxygen, autoignite!

(Note: I did this myself last month — accidentally — with olive oil in a wok that was too hot. Bad idea.) If you want to set anything aflame, you need to have the temperature rise above the Flash point of the material. For a match, striking the match head against an abrasive surface releases enough chemical energy to allow the underlying wood to ignite. For rubbing two sticks together, you have to put enough mechanical (i.e., frictional heat) energy into the system to get up to that temperature. And for a lighter, the metal sparks from rubbing the steel against flint are at a high enough temperature that they can ignite the butane gas:

But my favorite way to start a fire? Use a fire piston! (One of the things I demonstrated in my Welcome to Scienceblogs video.) Check out how it works below:

How it works: all you do is take an airtight tube with an airtight piston connected to it, and place a little bit of combustible material somewhere in the piston.

Then, compress the piston as quickly as you can. When you compress gas in an airtight container, there are two ways it can happen: isothermally or adiabatically. These fancy words basically mean that if you compress it slowly, the temperature will stay constant, but if you compress it quickly, the temperature will rise.

And if you compress it quickly enough, the temperature can rise by hundreds of degrees Celsius, enough to ignite many flammable materials! And that’s how, just by using your hands, you can start a fire in seconds!

So enjoy today — and every day — and choose your favorite way to make fire!

Comments

  1. #1 doug l
    April 20, 2009

    Fire…couldn’t really celebrate the date without it, actually.
    Hope you are too!

  2. #2 jon
    April 20, 2009

    That’s pretty awesome! Although I have one minor quibble (which I only mention because it’s a pet peeve of mine), when you say no chemicals, you mean excluding the combustible material which is made of chemicals and undergoing a chemical reaction.

  3. #3 Naked Bunny with a Whip
    April 20, 2009

    I’d like to remind everyone that the piston-compression technique of starting fires should not be used as a form of birth control. Thank you for your attention.

  4. #4 Sophos
    April 21, 2009

    Hmmm… Interesting. But piston is not something everyone has nor is it something one would bring along everywhere he goes…