I'm trying to understand why in 1900 (before Einstein's 1905 paper) Poincare came up with the same energy-momentum relation that you present here, and I'm not understanding why the momentum doesn't equal 2E/c when energy is defined as (1/2)mv^2 and momentum is defined as mv. Would you be able to shed some light on this for me? I'm no expert on electromagnetism, I haven't watched any of your other videos yet, and my math skills only go up to intro Calc, but I was able to follow this video quite easily.
RE example: At this level of physics and math, plug-and-chug doesn't really increase understanding. It's better to see how the values change vs. some other change. Perhaps that's what I'll do if I ever do a second version. RE momentum: It varies based on time, position, etc... Higher frequency means it changes much faster.
