Newton's Experiment Proving White Contains All Colors

Newton wasn't the first person to make a rainbow with a prism. Other people had already got the same result. But many of them thought the prism somehow 'coloured' the white light, like adding a dye. Newton's idea was quite different. He thought that white light was a mixture of all the colours, and the prism was just separating them from each other. He was right, and he proved it with a pair of neat experiments. First, he took his prism, as before, and stuck a narrow slit in the way of the co...

 Problems with Viewing the Cosmos Through the Atmosphere

The earth's atmosphere is an imperfect window on the universe. Electromagnetic waves in the optical part of the spectrum (that is, waves longer than X rays and shorter than radio waves) penetrate to the surface of the earth only in a few narrow spectral bands. The widest of the transmitted bands corresponds roughly to the colors of visible light; waves in the flanking ultraviolet and infrared regions of the optical spectrum are almost totally absorbed by the atmosphere. In addition, atmospher...