For centuries, scientists have tried different methods to determine the speed of light. (Prior to the 17th century, a common assumption was that light was infinitely fast, or at least impossible to measure.) Galileo tried an early method using lanterns, but was frustrated when he couldn't work it out. Many others tried various optical and astronomical methods, and eventually succeeded.

Weirdly, if those scientists had access to a microwave oven and some Peeps (okay, and a power source, and a working knowledge of physics), they could've gotten a pretty decent measurement in a few minutes. In this video, NPR's Adam Cole explains how to make it happen:

If you're hoarding stale marshmallows (they don't have to be Peeps), you can try this at home!