This video is about Richard Feynman's Quantum Electrodynamics (QED), which says that light is made of photons that go on all possible paths at once. The experiment in the video is from the following video from Veritasium. Even though I don't agree fully agree with their interpretation of the experiment, I think it's an excellent explanation of QED. Highly recommended! https://youtu.be/qJZ1Ez28C-A?si=adu1GrCF129cS65O