Have you ever wondered what makes a rainbow? This is a question that many children wonder about, and now, most parents have a ready answer (though some might encourage you to guess anyways!). But in the past, people didn’t know how these beautiful arcs of color formed in the sky. Some people were curious enough to ask why, but until the 1600s, no one did much more than make thoughtful guesses. It would take a mind nearly as bright as the sun to solve that and many other mysteries of how nature works. His discoveries paved the way for the modern fields of physics, astronomy, and math.
Early Life of Isaac Newton
The person who discovered what makes a rainbow was born into a rather dull world. Isaac Newton’s story begins on a sheep farm surrounded by apple orchards in rural England on Christmas day in 1642. Born prematurely to a poor family, no one expected the sickly infant to survive, but he did! Unfortunately, his father wasn’t so lucky. While little Isaac would live to be 84 years old, his father died three months before he was born. Isaac’s mother remarried to a well-off minister when he was two years old. Isaac never liked his stepfather and lived with his grandparents for much of his early childhood.
Isaac’s mind was so bright and active that he needed little else to hold his interest in the quiet hamlet where he lived. He wanted to know how the world worked and found all kinds of questions to occupy his mind. His mother, however, didn’t see much value in education, and after sending him to school briefly, pulled him out and tried to get him to help with the farm work. Isaac hated farm work–it kept him from exploring the many big questions about the world that flooded his head. Fortunately, Isaac’s uncle and his teacher both saw what a brilliant intellect he possessed. Seeing how poorly Isaac performed as a farmhand, his mother eventually took their advice and sent her son back to school.
Isaac flourished in school, where he studied Latin, Greek, and mathematics. When he had learned all he could at the local school, he headed off to Cambridge University. He mostly ignored his fellow students, even his roommate, and spent most of his time alone in his room. There he could let his mind play– with the ideas of the ancient philosophers, the observations of famous astronomers, and complicated mathematical formulae. His books, his quill pen, and the shadows creeping across the walls seemed to be the only company he needed as he delved into these subjects in a search for truth.
After graduating from Cambridge, Isaac returned home for two years. An outbreak of bubonic plague was sweeping England, and he felt it was best to isolate himself. This also suited Isaac’s preferences. He finally had an excuse to spend all his time alone in his studies, and he took full advantage. He spent his days reading, calculating, and setting up experiments.
Isaac Newton’s Experiments
Some of Isaac’s experiments didn’t work out. He tried to concoct a cure for the plague using rose water and turpentine, but it didn’t work. He also dabbled in alchemy, attempting to create gold from other, non-precious materials, a hobby he would come back to many times over his life. We now know this is impossible, but many people at the time thought it could be done.
Isaac’s experiments with light had better outcomes. He was fascinated by prisms, crystals shaped like triangles that create rainbows when light shines through them. Isaac was curious why this happened. Most people at the time thought that prisms somehow “corrupted” white light, adding in the colors of the rainbow, but Isaac suspected this wasn’t true. His experiments led him to the conclusion that plain white light from the sun was actually made up of all these different colors, and the prism split them apart.
In one experiment, Isaac set up three prisms in a row so that light from a window would shine through them, but their rainbow colors would overlap on the edges. Where the broken-up light from different prisms overlapped, the wall was white! The colors had mixed again into white light! He also lined up two prisms, putting a wall with a hole between them. He set up the first prism so that only the red light from the rainbow hit the hole in the wall and went on to hit the second prism. The red light passed through the second prism, hitting another wall beyond. This light couldn’t be broken up anymore, and of course, the second prism didn’t “add” colors to it, which should have happened if prisms worked the way other people thought. If Isaac rotated the first prism slightly, he could direct the blue, or yellow, or orange light to pass through the hole and onto the second prism. With each color he tried, the light hit at a different point on the final wall after passing through the second prism! Each color bent at its own special angle when it passed through the prism.
These were simple experiments–you could even ask your parents to buy some inexpensive prisms and try them yourself. Some of his experiments I wouldn’t recommend trying at home. He also tried to find out if he could see the rainbow colors of light by pushing on the back of his eyeball with a long, blunt sewing needle. Again, don’t try this at home! Still, Isaac’s unique mind let him imagine new ways to explore how light really worked instead of just believing what others had said before.
But, if you’ve heard one story about Isaac Newton before now, it’s probably about how he discovered gravity. That story recounts how an apple fell on his head and led him to the idea that there was a special force called gravity. This is also the story that Isaac liked to tell about the discovery! Gravity, Isaac theorized, is the force that makes larger objects, like the earth, pull smaller objects, like you and me and the apple, toward them. All objects, even very small ones, have gravity, but small objects only have a tiny bit compared to something as massive as the Earth. Isaac realized that gravity could explain not only the apple falling from the tree, but also the orbits of the moon and planets.
The idea of gravity led Isaac to think in new ways about how objects move. He experimented with motion and force, and formulated his three famous laws of motion based on these experiments. The first law was that if an object is at rest, or standing still, it would stay that way unless something came along and pushed or pulled it. Likewise, if an object was moving, it would keep moving in a straight line unless, again, something pushed or pulled it to make it stop. These pushes and pulls are called “forces.” The second law says that how much an object speeds up has to do with both how strong of a force is applied and how heavy the object is. Finally, his third law says that for every action, there is an equal and opposite reaction. In other words, forces come in pairs. Imagine you and a friend are ice skating. If you face each other, put your palms together, and push, both of you will be propelled backward. If you’re about the same size, both of you will go about the same distance. But if one of you is much bigger, the smaller person will go back farther and faster.
Newton’s Explorations in Mathematics
Isaac also worked out the math that explained his laws. Some of this math was fairly simple, but when it came to explaining gravity and the orbits of planets things got complicated. In fact, he developed a new branch of math called calculus to explain what he was seeing. Calculus is a kind of math used to describe things that are continuously changing, getting faster and slower. Think of the curve that a ball follows through the air when you throw it, or how fast a rocket is going at any given time as it blasts into space. These actions involve motions and forces and objects that are different weights and sizes. They get faster or slow down at different times. Very complicated!
Isaac Newton didn’t share his discoveries about calculus for a long time. He didn’t enjoy the attention his big discoveries brought him, and may have wanted to avoid it. He just wanted to discover the truth about how the universe worked. When he finally did tell people about it, another mathematician named Gottfried Leibniz had also come up with the same kind of math! Newton and Leibniz would both argue that they were first, but it didn’t really matter. Both were very smart and had come up with the ideas on their own.
After the plague died down, Isaac returned to Cambridge and became professor. He continued to spend most of his time studying and experimenting. He often ignored his own needs while deep in thought and study. He’d stay up late at night thinking, writing and experimenting. When he did sleep, he usually didn’t change into pajamas, and he went days without combing his hair. He ate simple meals of porridge or milk and eggs, and at times ate only foods from vegetables.
Isaac Newton’s Later Life
As Isaac got older, he began to take on some new and unexpected responsibilities. He was chosen to represent Cambridge University in Parliament, which is part of the government. True to his introverted nature, he rarely spoke up in debates. Later, he was chosen to run the Royal Mint, which was the part of the government that made money.
Isaac liked the capital, London, and moved there. Although he was never on good terms with his half-siblings from his mother’s second marriage, it seems he liked his nieces and nephews. He lived with his niece, Catherine Barton for many years, and left his papers and journals to her. He split the rest of his belongings between all his nieces and nephews.
Isaac Newton once wrote that truth was his greatest friend. Few people–if any–have contributed as much to scientific discovery as he did. We’ve only touched the surface of all his accomplishments. His work in calculus and physics launched an entirely new era in science. He set an example for future scientists by carefully designing experiments to answer very specific questions. His laws of motion helped later scientists send people to space on rockets and return them to Earth safely. He scrutinized the natural world and challenged assumptions about how things worked. The truth was his greatest friend, but he also proved himself a great friend to truth.
Krull, Kathleen (2013) Lives of the Scientists: Experiments, Explosions (and what the Neighbors Thought). Houghton Mifflin Harcourt, New York.