Igniting a Diesel-Air Mixture

At the bottom of a polycarbonate cylinder is a small ball of Pyro-cotton wool. If a piston is rapidly pushed into the cylinder, the cotton ignites and a bright flash of light appears.

How does it work?
The rapid compression of the air in the cylinder creates intense heat, which is sufficient to ignite the cotton wool. The same principle is used in a diesel engine, where a mixture of diesel and air is ignited by compression. Diesel engines therefore don’t require spark plugs.