Before Newton, standard telescopes provided magnification, but with drawbacks. Known as refracting telescopes, they used glass lenses that changed the direction of different colors at different angles.
After much tinkering and testing, including grinding his own lenses, Newton found a solution. He replaced the refracting lenses with mirrored ones, including a large, concave mirror to show the primary image and a smaller, flat, reflecting one, to display that image to the eye.
A drawing of Sir Isaac Newton dispersing light with a glass prism. The next time you look up at a rainbow in the sky, you can thank Newton for helping us first understand and identify its seven colors.
He began working on his studies of light and color even before creating the reflecting telescope, although he presented much of his evidence several years later, in his book, Opticks. Before Newton, scientists primarily adhered to ancient theories on color, including those of Aristotle , who believed that all colors came from lightness white and darkness black.
Newton disagreed. He performed a seemingly endless series of experiments to prove his theories. Working in his darkened room, he directed white light through a crystal prism on a wall, which separated into the seven colors we now know as the color spectrum red, orange, yellow, green, blue, indigo, and violet. Scientists already knew many of these colors existed, but they believed that the prism itself transformed white light into these colors.
But when Newton refracted these same colors back onto another prism, they formed into a white light, proving that white light and sunlight was actually a combination of all the colors of the rainbow. By trial and error, Kepler worked and worked until finally, he hit upon the shape that worked—elliptical orbits with the Sun at one focus. It turned out to perfectly fit the known observations. Kepler derived three numerical laws setting out not only the shape of the orbits, but also the relations between the distance from the Sun and the period of revolution.
They were stunning results, but no one knew why they would be true. But why ellipses, an egg shape? It was an open problem of the highest order. It was an anomaly in the classical paradigm. None of this was revolutionary. The basic concepts which ordered the universe and the picture of reality they gave rise to had become wobbly, but had not fallen.
Isaac Newton developed a simple theory—four basic laws: three laws of motion and the law of universal gravitation. An object not subject to an external force will continue in its state of motion at a constant speed in a straight line. Now, suppose someone is on ice skates, just standing in the middle of an ice rink. The person just stays in the middle of the rink. But if they are on ice skates and moving forward at two miles an hour, they will continue to move straight ahead at two miles an hour until something pushes them or stops them.
So, the first law describes the behavior of an object subjected to no external force. The second law then describes the behavior of an object that is subjected to an external force. So again, if a person is on ice skates moving forward at two miles an hour and they are pushed from behind, they now go faster in the same direction.
If they are pulled from behind, they slow down. If pushed from the side, they change direction. The bigger the push, the more the change; the heavier the object, the less the change. But what about the object or thing that applied the force? What happens to it? The force felt from a push is felt in the opposite direction, but in the same amount. Again, if a person is on ice skates and someone pushes them, they accelerate forward because of the force and the other person goes backwards because of it.
To every action there is always an equal, but opposite reaction. These three simple laws explained a lot, but they become incredibly powerful when combined with the fourth law—the law of universal gravitation, which says that gravitation is an attractive force, a very attractive force. Take any two objects with mass and there will be an attraction between them, along the lines connecting their centers of mass.
When the black plague closed Cambridge University, where he was a student, for two years starting in , he spent the long months locked up at home studying complex mathematics, physics and optics. It was during this fruitful time that Newton, with the help of a crystal prism, became the first to discover that white light is made up a spectrum of colors. He also developed the concept of infinite-series calculus, the kind of scary math studied today by engineering and statistics scholars.
By , Newton had even laid the blueprints for his three laws of motion, still recited by physics students everywhere:. What Newton didn't understand up to that point, and would spend the next two decades studying, was how those laws of motion related to the Earth, Moon and Sun — a concept he called "gravity.
Urged on and funded by astronomer Edmond Halley, who was also at Cambridge observing the path of a now-famous comet, Newton dove into the study of gravitational force in the s and '80s.
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