Part three of the ether series gets its hands dirty. Jonathan Drake and Polymath tear into the Michelson-Morley experiment, the so-called "nail in the coffin" for ether theory, and demonstrate that the experiment was built on a pile of unexamined assumptions that did the heavy lifting before a single beam of light was split. Then, they introduce one of the most foundational concepts of the series: principle and attribute. A wave is not a thing. It is what something does. A shadow has no properties of its own. Once you see it, you cannot unsee it. The episode closes with a live recreation of the double slit experiment using a laser pointer and a single strand of Jonathan's daughter's hair, producing a textbook wave interference pattern on the wall and, arguably, the most low-budget proof in physics history that something in this universe is most definitely waving.