The following “back yard” science experiment was copied from the “Times Online” website - I hope they don’t mind me re-publishing an excerpt of their article, but I thought it was so good it had to be shared.
The original article is called “Do Try This at Home”.
So how do you measure the speed of light with a bar of chocolate?
What do I need?
A bar of chocolate (the longer the better). A metric rule. A microwave oven.
What do I do?
Remove the turntable from your microwave oventhe bar of chocolate needs to be stationary. Put the chocolate in the oven and cook at high power until it starts to melt in two or three spots. This usually takes about 40 seconds. You should stop after 60 seconds maximum for safety.
What will I see?
Because the chocolate is not rotating, the microwaves are not evenly distributed throughout the bar and spots of chocolate will begin to melt in the high-intensity areas, or “hotspots”. Remove the bar from the oven and measure the distance between adjacent globs of melted chocolate.
What’s going on?
The frequency of the microwaves is the key. A standard oven will have a frequency of 2.45 gigahertz (the figure should be on the back of the oven or in the user manual). If your oven is 2.45GHz, the microwaves oscillate 2,450,000,000 times a second (you can adjust this figure depending on your oven). Microwaves are a form of electromagnetic radiation and therefore travel at the speed of light. If you know the frequency of the microwaves, finding out their wavelength will help you to calculate how fast they are travelling.
This is where the chocolate comes in. The distance between the globs of molten chocolate is half the wavelength of the microwaves in your oven, so double the measurement you have taken of the gap between the molten globs to find the microwave wavelength. In the New Scientist microwave oven the distance between the globs of molten chocolate was 6cm, so the wavelength in our 2.45 GHz oven is 12cm. To calculate the speed of light in centimetres a second you need to multiply this wavelength by the frequency of the microwaves: 122,450,000,000 = 29,400, 000,000, which is near to the true speed of light of 29,979,245,800cm a second (or 299,792,458 m per second).
Try it yourself, measuring as accurately as possible to get a figure even nearer to the true speed. If your chocolate bar is chilled beforehand, the molten areas tend to be more distinct when they first appear. You may find different chocolate bars, all of which taste delicious slightly melted, will aid your research. True scientists know that it is always important to double-check results.
PS: The hotspotsand consequent cold spotsthat occur in ovens thanks to the wavelength of microwaves are the reason why ants can survive unscathed and uncooked inside a switched-on oven. They immediately scurry to the cooler areas and ride out the microwave storm.
All credit for finding this article goes to my good friend and colleague Andrew, who writes at Novolocus. He’s an amazing repository of unlikely knowledge about the most interesting things - this being one of them.