Isaac Newton had tried for years to build a better telescope, and eventually built the first practical reflecting telescope.
Like most astronomers of the day, he was troubled by the blurry images and the halos of color that lenses produced.
Newton turned to a study of light to try to resolve the problem.
In Newton’s time, prisms were sold as toys because people liked to see the colors they produced when sunlight passed through them.
It was believed that white was the pure light and that the colors were some kind of variation on the white light. Newton used these toys to discover the basic principles of light.
Newton used a lens to focus the band of colors, or the spectrum as he called it, that the prism produced.
He found that each color was refracted, or bent, at a particular angle no matter how the prism was positioned.
Newton added a second prism to the experiment and discovered that none of the colors of the spectrum could be altered in any way. He concluded that they were the fundamental colors of light and that white light was a combination of all the other colors.
This also explained why the telescopes of Newton’s time produced blurred images surrounded with color.
The lenses inside the telescopes were not refracting light to one sharp focus. Newton had heard that a mirror with a specially shaped surface reflected, or bounced back, light to a single focus without the colors of a lens.
He built a telescope replacing one of the lenses with a mirror, and the images were much clearer and had no color halos.
These Newtonian telescopes are still built today using the same method.
Although Newton built the most sophisticated telescope of his time, he never made any systematic observations of the skies.
Newton was not always right.
He incorrectly believed in alchemy, the science of changing base metals into gold.