Peeps season passed its peak back at the beginning of the month with Easter. That means we all have to find a use for the leftover marshmallow bunnies and chicks before they get stale. NPR’s Skunk Bear science Tumblr found one: calculating the speed of light. It’s actually much easier than you might think. The only things you need besides a dish full of Peeps are a microwave and ruler. Just pop a full dish of leftover Peeps in the microwave and find the particularly melty spots. Those spots are where the microwaves are particularly intense, and they are half a wavelength apart. Since microwaves travel at the speed of light, finding the gooiest Peeps and measuring in between them will reveal the wavelengths. From there, you just multiply by the waves' frequency listed on the side of the microwave, and voilà: the speed of light. Check out the whole Peep-melting process, complete with a Peep Galileo, above.