This lecture has been viewed more than 10 million times. 1 million times on MIT's OCW, 6.5 million times in the channel "For the Allure of Physics" and 2.5 million times in this channel. Prof. Lewin put his life on the line to demonstrate that he is a strong believer in the conservation of energy. He explained why the sky is blue, why the clouds are white and why sunsets are red. The demonstrations are fascinating. MIT video streamed this lecture in real time. It was viewed live by about 25 thousand people all over the world.