How to arrive at E=mc2
It only needs four thought experiments to get you from the fact that the speed of light is always constant to the famed formula E=mc2. youtube
Kohlmann & Co.

It only needs four thought experiments to get you from the fact that the speed of light is always constant to the famed formula E=mc2.
[youtube https://www.youtube.com/watch?v=Ilb4M9MWmlc?rel=0&w=1280&h=720]