In the animation, you see a total lunar eclipse — a phenomenon during which the Moon sinks into the earth’s shadow. But some of the sunlight still penetrates into the shadow, refracting in the earth’s atmosphere. It is this light that turns the moon red. But why red? The same mechanism works here as when painting sunrises and sunsets: the earth’s atmosphere scatters the short-wave part of the solar spectrum (blue, blue) and leaves only the long-wave, just red and orange colors.