In the Americas alone more than one billion people in 35 countries could bear witness to the total lunar eclipse.

White light is made of a spectrum ... a prism. There are three primary colours of light, which can be combined to make secondary colours. A rainbow contains all the colours of the visible spectrum.

The standard design is simple; a prism or diffraction grating to break up a light source into a spectrum and a detector to measure light intensity. Shine the light through your sample, scan ...