Exploding grease, exploding microwave ovens, exploding cheese — it’s a Mythbusters fan’s dream episode :-) Of course, where there are explosions, there’s physics, and the latest episode of Mythbusters is no exception.

Here’s one: you can’t blow up C-4 by microwaving it. Kari explained in the show that this is because C-4 is a plastic explosive, and microwaves are designed to pass through plastics (as well as metal and glass). So how exactly does that work?

Microwaves heat food by a process called dielectric heating, which generally refers to the ability of many materials to absorb energy from electromagnetic radiation passing through them. Physically, an electromagnetic wave consists of rapidly oscillating electric and magnetic fields. These fields (well, primarily the electric field) exert forces on the charged particles that make up all matter — since the fields are oscillating, so do the forces. Essentially, an electromagnetic wave makes atoms and molecules rapidly jiggle back and forth, and as they do so, they bump into other nearby atoms and molecules, transferring kinetic energy to them and raising their temperature. Of course, if the atoms and molecules are gaining energy, that energy must be coming from somewhere, and the electromagnetic …