Being the geek that I am, I cannot wait until my daughter is old enough to show her a science experiment that is not only fun to do but tastes great too! Teach your kid how to calculate the speed of light using marshmallows!

 This activity is going to require a few things. Grab a ruler, a bag of marshmallows, a microwave-safe casserole dish, and head to the microwave. Your microwave needs to be an old-style type without the turntable or just remove it before doing this experiment.

First, open the marshmallows and place them in the dish; completely covering the bottom with a layer. Begin heating the marshmallows on low heat and cook until the marshmallows being to melt in a few different spots. What’s happening here is that the microwave doesn’t heat evenly throughout the dish. Turntables help distribute the microwaves throughout the food by turning the dish as the microwaves pass through. This would have been a problem.

After you see a couple of spots begin to melt, stop the microwave and take the dish out. It would be best if the parent handles this part of the experiment just to be sure we don’t end up having a kid in the ER with a burn because of science.

Take out your trusty ruler and measure the distance between the melted spots and average out the distance. You’ll notice that you are getting a common result, roughly about 6cm which is the half wavelength of the microwave. Turn your microwave oven around and look for a sticker that shows the frequency of the oven. Most microwaves run at approximately 2450 Mhz.

Now we need to do a bit of math.

1. First determine the actual length of a microwave. The distance between the melted spots was approximately 6 cm, double that to get the entire wavelength. We now have 12cm.

2. The formula for determing velocity is as follows:

Velocity = Frequency x Wavelength

Velocity = 2450 Mhz x 0.12 m

Velocity is 2,450,000,000 Hz x 0.12m

Velocity is 294,000,000 m/s which is VERY close to the actual speed of 299,792,458 m/s!

Depending on the age of your child and how in depth you would like to go, take the time to explain how the microwave actually works and how you calculated the length of the microwave. In 5 minutes, you’ve taught your child some important information about the travel of electromagnetic waves, the speed of light, and how good a gooey marshmallow can taste! Enjoy.