It’s not camera-hacking elves: If you take your North American smartphone to Europe and shoot video indoors there, an odd flickering appears in the recording. As intrepid videographer Tom Scott shows above, it’s because of something normally invisible—the differences in how the two continents transmit electricity.
It’s an awesome video, interesting even if you’ve never bounded the Great Circle.
I like it partly because it reveals how wave-bound media—light, electricity, and sound—work similarly. Computer screens, for example, flicker on film for the same reason Europe’s lights do. If a camera frame rate and a screen’s refresh rate are different, the two hidden frequencies appear as a larger modulation. Ditto stringed instruments: If you play a sustained note on an out-of-tune piano, it will seem to “beat”—steadily rising and falling in volume—because it’s out-of-frequency with itself.