Use Your Microwave to Calculate the Speed of Light

Over at Gizmodo, there's an article about calculating the speed of light by melting chocolate in your microwave oven. Basically, you remove the spinny-thing from your microwave and begin to melt some chocolate in it. Take out the chocolate, and measure the distance between the melty-points. This is the half the wavelength of the microwaves in your oven. Why half? Think of a sinusoidal wave. One of the melty spots is a peak and the next is a low point and the next is another peak. The wavelength is the distance from one peak to the next peak.

So, you measure the distance between two melty spots and multiply that by two. That's your wavelength. Oh. Measure it in meters. Be civilized.

Now multiply that by 2,450,000,000. This is the frequency (in hertz) of the microwaves used in microwave ovens.

Your result should be the speed of light.

(Well, not really. If you were doing this in a vacuum and measured really carefully, then it should be. With this method you should be vaguely in the ballpark, though. That's still cool, right?)

Why does this work?

Because I'm sleepy, I'll give you the oversimplified version:

When we say that 2,450,000,000 is your microwave's frequency, what we are saying is that that the wavelength crosses the space 2,450,000,000 per second. Wavelength is a unit of distance. If the microwave moves that distance 2,450,000,000 times each second, then that tells us its speed. The speed of microwaves (which are a sort of electromagnetic energy aka light).

Two observations:

1. I already know the speed of light. I do not, of the top of my head, generally know the frequency of microwaves used by my microwave oven. Why not use it to calculate that, instead.

2. Why waste good chocolate on this? Anything that melts (or browns in the microwave) should work.

via Serious Eats