In science, we often say things like "all scientific results must be replicable." If you have one researcher who says "I've measured the speed of light to be 3-million meters per second." another researcher has to be able to get the same value doing the same experiment. For laypeople, sometimes we just have to take their word for it. I mean, I don't know about you, but I don't have a multi-million dollar laboratory in my garage (dangit). However, you and I do have options. For instance, did you know you can measure the speed of light without leaving home, using things most of people probably have laying around already? Yep. It's true.

Do you have a microwave? Do you have a hot dog sausage that's lonely because you ate all the buns?

If so, Congratulations, you have what it takes to measure the speed of light within 2% or 3% accuracy! Moreover, I'm going to walk you through the process.

If it isn't completely removable, then you should disconnect it from the turning wheels. The moral of the story is, you want the turning plate to remain stationary while the microwave is on.

It should look something like this:


Let it run until the hot dog starts to bubble. This should only take a few seconds, so don't go anywhere. If you over heat the hot dog, you'll need some condiments so you can eat this one because it'll be worthless for the rest of the experiment (and, you'll probably want a second dog to try again).

Anyway, after you're done, you'll see something like this.

You should see two bubbles on the hot dog.

The next thing you'll need to do is measure the length of the bubbles, starting from the beginning of the first bubble to the end of the second one. Measuring in centimeters is best because you'll need to convert that to meters in just a minute. The bubbles below measure 12.5 centimeters.

On the sticker found on the back of the machine, you'll look for the "Microwave Output" line and look for a value that says something like "2450MHz" - if you can't find it, most microwaves use this same frequency, so you can use this value. When we convert that to 2.45GHz because we need this value in giga hertz (to covert your frequency from MHz to GHz just devide the MHz number by 1000).

Giga means billion, so that number is really [latex]2.45times 10^9[/latex]Hz.

To convert cm to m, we just divide the cm value by 100, in our case, we get 0.125 m.

The speed of light is equal to it's frequency times it's wavelength, or:

Speed = Frequency x Wavelength.

So, we have,

[latex]huge 2.45times 10^9ast 0.125=306,250,000 m/s[/latex]

The speed of light is actually 299,782,458 m/s.

To calculate how close you were, you use the form:

[latex]huge frac{real-you}{you}*100[/latex]

where you is your value and real is the accepted value for the speed of light.

So, we get:


So, you've just calculated the speed of light to within 2.11% error. (note, ignore signs for the above calculation, if it's -2.11% or +2.11% it doesn't matter).

If you performed this experiment, tell us your results below and have fun scienceing!

Oh! The last step is very important. Finish cooking the hot dog and eat it. You just calculated the speed of light. You earned this.


Think this experiment is cool? Learn how you can create your own cosmic ray detector here.

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