Who Was Isaac Newton?

by Janet Pascal

  Who Was

  Isaac Newton?

  By Janet B. Pascal

  Illustrated by Tim Foley

  Grosset & Dunlap

  An Imprint of Penguin Group (USA) LLC

  For Professor Owen Gingerich, whose demonstration of Newton’s third law I will never forget—JPB

  GROSSET & DUNLAP

  Published by the Penguin Group

  Penguin Group (USA) LLC, 375 Hudson Street, New York, New York 10014, USA

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  Text copyright © 2014 by Janet B. Pascal. Illustrations copyright © 2014 by Tim Foley. Cover illustration copyright © 2014 by Nancy Harrison. All rights reserved. Published by Grosset & Dunlap, a division of Penguin Young Readers Group, 345 Hudson Street, New York, New York 10014. GROSSET & DUNLAP is a trademark of Penguin Group (USA) LLC.

  Library of Congress Cataloging-in-Publication Data is available.

  ISBN 978-0-698-18725-2

  Version_1

  Contents

  Title Page

  Dedication

  Copyright

  Who Was Isaac Newton?

  Lonely Boy

  Cambridge

  The Plague Years

  Falling Apples

  The Wonderful Telescope

  Fighting about Light

  A Secret Life

  A Competition

  Newton’s Big Book

  Laws of Motion

  Becoming a Legend

  Battles at the Royal Society

  Genius

  Timelines

  Bibliography

  Who Was Isaac Newton?

  In 1665, a terrible sickness swept through England. It was called the plague. It caused huge swellings all over the body and made people’s skin turn black. There was no cure. Most people who caught it died a quick and painful death. Any place people lived crowded together was dangerous, because plague was very easy to catch. No one knew what caused it, or how to protect themselves against it. The only way to stay safe was to go to the countryside, where there were fewer people to catch it from.

  A twenty-three-year-old student named Isaac Newton had to leave Cambridge University and flee to his mother’s farmhouse. He didn’t really mind. He had always been a loner. He didn’t have friends he would miss. At his mother’s house, he spent the time doing what he did best—thinking about the universe.

  One day he saw an apple fall. He began to wonder what pulled the apple toward the Earth. And so, according to the famous legend (which might even be true), young Isaac Newton thought up the idea of gravity.

  The plague years were a terrible time for most people, but not for Newton. For him, they were a wonderful time of discovery, and not just about gravity. He came up with enough new ideas to keep him busy thinking and writing for the rest of his life. His ideas helped people understand how the universe worked in a new way.

  After eighteen months, Newton went back to Cambridge, but he never did make many friends. He was jealous and unfriendly, and he lost his temper easily. He wasn’t a very nice person, but he was one of the greatest scientific geniuses who has ever lived.

  Chapter 1

  Lonely Boy

  Isaac Newton was born in Lincolnshire, England, on Christmas Day 1642. (Because England used a different calendar then, his birthday is also given as January 4, 1643.) He didn’t seem to have a great future. At first, it didn’t seem he had any future at all. He was born too early. He was weak and so tiny he could fit into a quart mug. No one thought the sickly baby would live, but he did. His father, also named Isaac, had died three months before his son’s birth. He had been a well-off farmer, but he couldn’t read or write—not even enough to sign his name.

  THE ENGLISH CIVIL WAR

  NEWTON WAS BORN RIGHT AT THE BEGINNING OF THE ENGLISH CIVIL WAR. DURING HIS CHILDHOOD, THE KING AND PARLIAMENT WERE LOCKED IN A BLOODY STRUGGLE. IN 1649, WHEN NEWTON WAS SIX, KING CHARLES I WAS PUT ON TRIAL AND BEHEADED. A STRICT GOVERNMENT WITH NO KING TOOK POWER. ELEVEN YEARS LATER, IN 1660, THE MONARCHY WAS RESTORED UNDER CHARLES II. ALTHOUGH NEWTON’S FAMILY WAS NOT PERSONALLY INVOLVED IN THE WAR, THE VIOLENCE AND UNCERTAINTY OF THE TIME HAD AN IMPACT ON HIS CHILDHOOD.

  When Isaac was only three, his mother, Hannah, got married again, to a minister named Barnabas Smith. Smith wanted a wife, but not a son. Hannah agreed to move into her new husband’s house, leaving Isaac behind with her parents.

  Little Isaac almost never saw his mother, and he was very lonely. Sometimes he would climb a tree so he could stare at his mother’s new home. He hated his stepfather so much that he imagined burning down the house with him in it. When Isaac was ten, however, his stepfather died. His mother moved back, bringing with her a half brother and two half sisters for Isaac.

  Isaac went to the little local village school, which didn’t teach much beyond how to read. He seemed unusually intelligent, so Hannah decided to send him to a better school. The King’s School was seven miles away—too far to walk—so Isaac lived with the Clarke family in town. The family later said that while he lived there, Isaac fell in love with Clarke’s daughter Catherine. If this is true, she was the only girlfriend he ever had. Years later Catherine remembered him as “a sober, silent, thinking lad” who was never known to “play with the boys . . . at their silly amusements.” In his spare time, he built doll furniture for Catherine.

  Clarke was an apothecary. An apothecary is someone who makes medicine by combining herbs and chemicals. This involved careful work with weights and measures, as well as knowing what was special about different substances. Young Isaac was fascinated. By watching and perhaps helping Clarke, he began to learn basic chemistry—how different things interact with each other. He even created his own potions, such as a medicine made up of turpentine, rosewater, beeswax, olive oil, a kind of wine called sack, and red sandalwood. This was meant to protect him from a deadly disease called tuberculosis.

  Isaac was also fascinated by ways to keep track of time. The clocks of the day weren’t very accurate, and he thought he could do a better job. He charted the movement of shadows from sunrise to sunset. Then he hammered pegs into the wall to create a sundial. When people wanted to know the real time, they’d check “Isaac’s dial.” For telling time indoors, he designed a clock with a wooden dial turned by the steady dripping of water. He also built a tiny windmill, with a mouse to run it.

  Unfortunately, the subjects taught at school didn’t interest him. He didn’t study, and he was at the bottom of his class. One day a boy who was a good student kicked him in the stomach. Isaac immediately challenged him to a fight, which, to everyone’s surprise, he won. Isaac was very good at holding a grudge. Just winning the fight wasn’t enough for him. He wanted to beat his enemy in school as well, so he finally began to study. Soon he rose to the top of the class.

  The main subjects at school were Latin and Greek. Both would be useful to him later on, because almost all the most important books and articles were still written in these languages. He may have also learned some simple, useful arithmetic and geometry.

  Hannah thought of educa
tion mainly as a way to make her son a good farmer. Soon she decided it was time for him to practice running a farm, so she took him out of school. The idea of growing crops and taking care of animals bored Isaac. He deliberately did a bad job.

  When he was supposed to be working, he sat under a hedge reading or building things. Once when he was supposed to watch the sheep, he let them run into a neighbor’s field and eat the crops.

  His mother was hauled into court and had to pay a fine after that happened. Isaac was not turning into the kind of farmer his mother hoped for.

  Chapter 2

  Cambridge

  Luckily, Isaac wasn’t the only one who hated the idea of his becoming a farmer. The master of his school thought it was a waste of a brilliant mind. Along with Isaac’s uncle, he managed to talk Hannah into letting her son go to a university. So at eighteen, Isaac Newton left for Trinity College. This was part of Cambridge University. He would spend the next forty years living there, first as a student and then as a professor.

  Newton’s first months at Cambridge were a letdown. Even though Hannah was well-off, she didn’t want to pay his fees, so he had to enter as what was called a sizar. This meant he worked as a servant to the richer students.

  Most of them were more interested in having a good time than in learning. Newton despised them. He grew less lonely when he met another serious student, John Wickins. They moved in with each other and lived together for the next twenty years. Wickins was one of the few people Newton ever stayed friends with for long. Unfortunately Wickins never wrote down his memories of Newton.

  Study at Cambridge was still based on ancient Greek and Latin philosophy, especially the writings of the Greek philosopher Aristotle. Aristotle was a brilliant man—the Newton of his time—but he had lived in the fourth century BC. Over two thousand years later, knowledge in many areas hadn’t moved much beyond what he taught.

  Aristotle based his theories on observation of the world around him. However, it was even more important to him for an idea to make sense. He didn’t always test his ideas against reality. For instance, he thought that human males, being bigger and stronger, would have more teeth than human females. That seemed reasonable to him. If he had actually looked in men’s and women’s mouths, he would have seen that he was wrong. In the centuries after his death, other scholars often just accepted what Aristotle had said as the truth.

  IN NEWTON’S TIME, VERY FEW PEOPLE ACTUALLY GOT TO GO TO COLLEGE. THERE WERE ONLY TWO UNIVERSITIES IN ALL OF ENGLAND: OXFORD AND CAMBRIDGE. BOTH WERE ANCIENT. THEIR MAIN PURPOSE WAS TO PREPARE STUDENTS TO BE MINISTERS IN THE CHURCH OF ENGLAND, AND ONLY MEMBERS OF THE CHURCH WERE ALLOWED TO ATTEND THEM. EVERY STUDENT HAD A PERSONAL TUTOR WHO TOOK CHARGE OF HIS EDUCATION. MANY OF THE UPPER-CLASS STUDENTS, HOWEVER, WERE ONLY THERE TO HAVE A GOOD TIME.

  Much of what was taught at Cambridge didn’t interest Newton, and he paid little attention to it. What Cambridge did offer was a library full of books.

  Over the past few centuries, daring scholars had been challenging the old ways of explaining how the world worked. The word scientist hadn’t been invented yet—these scholars were known as natural philosophers. They became the founders of modern science. Newton set out to learn from them.

  Newton read the ideas of Nicolaus Copernicus, one scholar who challenged Aristotle. Aristotle thought that the Earth was the center of the universe and all the other heavenly bodies moved around it. In the sixteenth century, Copernicus suggested it made more sense to think that the Earth and all the other planets moved around the sun. This seemed reasonable to Newton.

  Aristotle’s idea felt right—it certainly looks to us like everything revolves around the Earth. But anyone who actually watched the planets in the sky could see that sometimes the way they moved didn’t match what Aristotle described.

  People came up with all sorts of complicated ideas to explain why the planets didn’t behave as Aristotle said they should. But if they stopped trying to force the planets into Aristotle’s system and switched to Copernicus’s system, with all the planets traveling around the sun, everything suddenly made sense. The planets moved just the way Copernicus’s theory predicted.

  Newton also read the work of Johannes Kepler, who had built on Copernicus’s work.

  Copernicus had suggested that planets moved in circles around the sun. Kepler tracked the planets’ movements carefully and discovered their exact paths. They were not circles but a kind of oval called an ellipse.

  Then there was Galileo, an Italian who died the year Newton was born. He looked at the heavens through a telescope and reported on the surprising things he saw. For instance, the moon was covered with mountains and craters, and there were spots on the sun. Aristotle said that heavenly bodies must be pure and more perfect than anything on Earth. What Galileo actually saw made him disagree. Even out beyond the moon, it looked as if things were made of the same ordinary material as on Earth.

  Galileo believed in testing the truth of what other people told him. For instance, Aristotle said that heavy objects fell faster than light objects. That certainly sounds reasonable, but Galileo wondered if they really did. He came up with experiments to find out, by dropping balls and measuring how fast they fell. According to legend, Galileo dropped balls from the leaning Tower of Pisa. That isn’t so. Nevertheless, he did discover that Aristotle was wrong. Objects of the same size and shape, dropped from the same height, fall at the same speed, no matter how much—or how little—they weigh.

  From reading these men’s works, Newton learned something. It didn’t matter how reasonable an idea seemed. It had to match what could actually be observed. If the world didn’t do what an idea said it would, it was time to come up with a new idea.

  At Cambridge, Newton began to teach himself mathematics. This interest grew out of a visit to Stourbridge Fair. The fair was a huge outdoor gathering with farmers and tradesmen selling everything from farm animals to clothing to toys. Full of young couples, dancers, and performing animals, it was a much more frivolous place than Newton usually liked. But he did find a bookseller there, and he bought a book on astrology.

  Astrology is the belief that the stars and planets rule people’s lives. Astrologers use the heavens to predict the future and try to control events on Earth. Astrology had become very complicated, using elaborate calculations and charts.

  Many people in Newton’s time believed in astrology, so he was curious about it. Before he had read very far in his new book, Newton came to an example that used a kind of difficult mathematics he didn’t know. He bought another book to teach himself about it. But before he could understand this new book, he had to know a more basic branch of mathematics that he hadn’t learned yet. So he had to back up and start at the beginning.

  In 1665, Newton passed the exams for his bachelor’s degree. His grades were not very good. Most of the exam questions were about subjects that didn’t interest him. Still he did well enough to become a scholar. This meant he could keep living and studying at Cambridge, with free room and board. Almost as soon as he earned the right to stay at Cambridge, however, he had to leave.

  Chapter 3

  The Plague Years

  In 1665, the plague broke out in England. The university was closed, and Newton went home to Lincolnshire.

  For the next eighteen months, he lived at home. Newton had never much liked being with other people. He was happy to be left alone to think about exactly what he wanted. This was the most productive time of Newton’s life. He later remembered, “In those days I was in my prime of age for invention.” By invention he meant being able to think up new ideas.

  What was he thinking up? A new kind of mathematics, to start with. The math he knew was fine to use for some kinds of problems. If you knew how fast a wagon was going and that it was moving in a circle, it was easy to figure out where it would be an hour later. However, Newton was interested in a different kind of problem. H
e wondered about things that were changing all the time. What if you shot a cannonball into the air? First it would travel in a curve upward, slowing down more and more. Then it would get to the top of its path and start curving back down toward the Earth. As it got nearer to the ground, it would move faster and faster. Its speed and its direction were always changing. How could you create a mathematical equation that would describe this kind of movement when it was never the same for an instant?

  THE PLAGUE AND THE GREAT FIRE

  WHEN THE PLAGUE STRUCK, LONDON BECAME A CITY OF DEATH. AS MANY AS ONE IN FIVE PEOPLE WERE KILLED BY THE DISEASE. THEN IN SEPTEMBER 1666, JUST AS THE PLAGUE WAS BEGINNING TO DIE DOWN, A GREAT FIRE BROKE OUT. STARTING IN A BAKERY, IT BURNED FOR THREE DAYS. MOST PEOPLE MANAGED TO ESCAPE, BUT 80 PERCENT OF THE BUILDINGS IN LONDON WERE RUINED. ALTHOUGH NO ONE KNEW IT, THE PLAGUE WAS CARRIED BY RATS AND FLEAS. BY DESTROYING ALL THE FILTHY OLD BUILDINGS WHERE THE RATS LIVED, THE FIRE MAY HAVE HELPED END THE PLAGUE.

  Newton invented his own form of mathematics—one that could handle this kind of question. He called it the method of fluxions. Fluxion means “continual change.” Today we call his invention calculus. Modern physics, the study of motion, matter, and energy, would not be possible without it.