Great scientists
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Isaac Newton
The work of English scientist Isaac Newton (1642–1727) was probably the main factor in triggering an exciting period of history, known as the Age of Enlightenment, where many ideas we take for granted today were being put forward for the first time. His discoveries were the last and greatest of the explosion of scientific research known as the Scientific Revolution, which is usually said to have begun in 1543 with the publication of the work of Nicolaus Copernicus. Newton's contribution included greatly furthering our understanding of the laws of motion, how gravity works and the nature of light and colour. Although modern physics explains matter and energy in a very different way, many of Newton’s ideas are still useful today, and have provided the basis for modern science. His equations are in daily use by scientists.
Early life
Isaac Newton was born in the village of Woolsthorpe, Lincolnshire, in 1642. He was educated at local village schools and then at The King’s School in Grantham where he was taught Latin, Greek, Hebrew and mathematics. He lodged with the town’s apothecary (pharmacist), William Clark. Although Newton did not excel at school, his headmaster recognized that Isaac had unusual talents, and persuaded Newton’s mother to allow her son to go to Cambridge University in 1661.
Scientific career
There was little formal science teaching at Cambridge. Newton was expected to study the classics (Latin and Greek) with some mathematics, but his fascination with science led him to spend his spare time researching the work of the great scientists of the age, including the Italian astronomer Galileo (1564–1642), and the French philosopher René Descartes (1596–1650).
Newton graduated in 1665, and planned to stay in Cambridge, where he now had a scholarship to provide an income. But his time there was interrupted by a severe outbreak of bubonic plague that started in London and soon affected many other parts of England. Newton returned to Woolsthorpe, but continued his scientific work. Here he made some of his greatest advances in mathematics and physics.
Calculus
During this period Newton worked on highly complex mathematics, including something he called fluxions, now known as calculus. This branch of mathematics deals with quantities that are constantly changing, such as changes in speed as an object accelerates. It can also be used to work out the length of a curved line, which can be seen as an infinite number of tiny straight lines, joined end to end.
In fact, the German mathematician Gottfried Wilhelm Leibniz (1646–1716) worked on the same idea at the same time, and the rivalry between Leibniz and Newton over who discovered calculus raged for the rest of their lives.
Light
Newton also studied light, which he thought was made up of tiny particles. At the time it was generally thought that colours were made up of a mixture of light and darkness. Doubting that this was true, Newton carried out an experiment in which he projected a beam of light into a prism, a transparent object with straight sides and triangular ends. He saw that the prism broke the light up into bands of colours, which we now call the spectrum. He showed they could even be recombined by using another prism to form the original light.
This led Newton to conclude that white (colourless) light was made up of all the colours mixed together, a theory that he published in his 1704 work, Opticks. In it he also explained how rainbows were formed.
Gravity and motion
One of Newton’s most famous ideas was about how gravitational force (gravity) works. It is said that he came up with this while he was at home in Lincolnshire, and saw an apple fall from a tree. Both the apple and the Earth have gravity, but because the Earth is huge compared to the apple, we see the apple moving towards the Earth and not the other way round. Newton proposed that the same gravitational force that pulls the apple attracted the Moon to the Earth and kept it in orbit around it.
Newton was not the first scientist to think about gravity—Galileo had already written about it in the early 1600s—but Newton went further, by suggesting that it applied to objects both on Earth and in space.
Laws of motion
Newton worked on his ideas about gravity and motion for around 20 years before he eventually produced his most famous work, Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) in 1687. In this, among other things, he defined the universal laws of motion.
The first law of motion. An object that is moving steadily will continue to do so until force is applied to it, and something that is not moving will only do so when force is applied to it. For example, a cannon ball fired from a gun will continue to travel through the air until something stops it—that "something" eventually being the force of air resistance, friction caused by the presence of molecules that make up the air.
The second law of motion. The acceleration of an object depends on two things: its mass, and the force acting on it. As the force increases, so does its acceleration (that is, if you push something harder, it will move faster.) But if the mass of the object is larger, it will take more force to accelerate it to the same speed. Put another way, Force = Mass x Acceleration
The third law of motion. For every action, there is an equal and opposite reaction. So if you press against something—a spring, for example—it is pushing just as hard against you.
Universal gravity
Newton also wrote in Principia that every object in the Universe attracts every other object, and that the force of the attraction, which is gravity, acts as if all the mass of an object is concentrated at its centre. The strength of this force depends on the mass of the objects and the distance between them.
Last years
With the publication of Principia in 1687, Newton became famous. He was briefly Member of Parliament for Cambridge University and moved to London. In 1689, he became warden of the Royal Mint, where he designed new kinds of coins that were harder to forge than earlier ones. Newton was eventually made president of the prestigious Royal Society, a learned society for science founded in 1660, and was knighted. When he died in 1727, his funeral was held in Westminster Abbey.
Consultant: Mike Goldsmith