This lecture has been viewed about 18 million times. About 1 million times on MIT's OCW, 7 million times in the channel "For the Allure of Physics" and about 10 million times in this channel. Walter Lewin puts 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. Great demonstrations! MIT video streamed this lecture in real time. It was viewed live by about 25 thousand people all over the world.