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Archive for the ‘1600s’ Category

Newton

Isaac Newton (1642-1727) discovered the three laws of motion and the law of gravity. He wrote about it in his book, the “Principia” (1687). It laid the foundation of a new and better physics in the West after the fall of Aristotle’s physics in the early 1600s. It made physical sense out of the theories of Copernicus and Kepler.

The old physics of Aristotle only told you what happened in general. With Newton you could work out the numbers in detail for yourself and predict what would happen. It was that good.

Both Newton and Kepler were numerologists: like
Pythagoras, they played with numbers endlessly, believing they held the key to the mysteries of the universe. For them it worked: They both succeeded in discovering laws of nature where numbers played an important part. This gave science in the West its great faith in numbers and laws of nature.

Newton built on the physics of Galileo, but he did two things that Galileo did not do:

  1. Newton took Kepler seriously.
  2. Newton added the idea of a force of nature acting at a distance: one thing could affect another across empty space. Magnets are just one example of this.

Legend has it that Newton once sat under an apple tree thinking about the motion of the moon. Just then an apple struck him on the head. In that moment he saw how both the moon and the apple followed the same law of nature: the law of gravity.

Gravity is the force that on earth causes things to fall.
Anything made of matter has gravity, but the larger it is the more gravity it has. Even a stone has gravity – but it is too weak to notice. The earth, however, is so large that it pulls everything near it to itself. That is why things fall.

In the case of the moon, it does not fall to earth because it is going so fast that it goes in a circle round the earth, attempting to break loose but never quite succeeding. In a sense the moon is falling forever.

But the force of gravity falls off quickly – by the square of the distance. For example, it is only a fourth as powerful at two times the distance; a ninth as powerful at three times the distance, and so on.

Newton’s three laws of motion:

  1. Absent any force, an object at rest remains at rest; an object in motion remains in motion – in the same straight line, going neither faster nor slower.
  2. F = ma. Force (F) is measured by the amount of mass (m) something has (on earth this is the same as its weight) times the acceleration (a) (how much faster the mass is forced to go).
  3. Every action has an opposite and equal reaction.

The first comes from Galileo.

Applying these three laws to those of Kepler, Newton worked out the law of gravity.

Physics was largely unchanged until the theories of Einstein and quantum physics in the 1900s.

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Kepler

Johannes Kepler (1571-1630) was an astronomer of the early 1600s who developed and perfected the theory of Copernicus. He worked with Tycho Brahe, who carefully observed and recorded the positions of the planets in the sky. From this Kepler found that the theory of Copernicus was not that good at predicting where planets would be. It needed work.

Even Copernicus knew that planets did not move in simple circles. Like Ptolemy, Copernicus had circles within circles – epicycles. But even then it still did not quite fit the facts.

Kepler figured out what was really going on: planets did not move in circles or even circles within circles, but in ellipses: less than perfect circles that were longer one way than another. In addition, planets moved both fast and slow in a predictable way.

Kepler’s system was not only better, it was simpler.

Kepler came out for the theory of Copernicus 37 years before Galileo did! What is more, he knew the theory was not perfect and set about to make it better.

Even though Galileo knew of Kepler’s improvements, he still preferred Copernicus.

Kepler was Protestant not Catholic. The Catholic Church could not silence him as it did with Galileo. The Protestant churches were against the theory of Copernicus too, but were too weak. They could not silence Kepler: all they could do was to make life difficult. He often lost his home and his position at universities. He was always on the move, it seemed.

Tycho’s 20 years of observations of the planets were not perfect, as Kepler knew, but they were by far the best in the world. Based on them Kepler wrote his “Nova Astronomia” in 1609. It laid out the first two of his three laws – the first laws of nature given by anyone:

  1. A planet moves round the sun in an ellipse.
  2. The line between a planet and the sun sweeps across equal areas in equal time.

The effect of the second law meant that as a planet got closer to the sun, it began to move faster and as it got farther away it moved more slowly. Because a planet moves in an ellipse it is not always the same distance from the sun.

He came out with his third law some years later:

  1. To figure out a planet’s year (the time it takes to go round the sun) take the cube of the square root of its average distance.

For example, Jupiter is 5.2 times farther from the sun than the Earth. The square root of 5.2 is 2.28 (because 2.28 times 2.28 equals 5.2). The cube of 2.28 – 2.28 times 2.28 times 2.28 – is 11.85. So Jupiter takes 11.85 years to go round the sun.

Kepler had no idea why any of this was true or how it was possible physically – no one did till Newton in the late 1600s. But to his great credit he followed the facts as he knew them.

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Galileo

Galileo (1564-1642) was a founder of Western science and the first to look at the night sky through a telescope. What he saw brought him face to face against the Catholic Church. The Church condemned and silenced him but they could not silence his ideas.

He was one of the first to use experiments to do science, where ideas are put to the test to see if they are really true. He found holes in Aristotle’s physics.

The telescope made things far away seem nearer. Galileo did not invent the telescope but he was the first to point it at the night sky. It was like going up into the sky yourself.

He was the first to see the mountains on the moon, the stars in the Milky Way, the spots on the sun, the moons of Jupiter and the the waxing of Venus.

This all came as a shock.

In the universities they taught the theories of Ptolemy and Aristotle: the sun and all the planets circled round the earth and the heavens were perfect and eternal. The Church never declared Ptolemy and Aristotle to be doctrine, but the theories of both had stood for hundreds of years and seemed like eternal truths.

But as Galileo found, they were not. His experiments in physics and what he saw through his telescope cast serious doubts upon both. He found that Copernicus was right after all: the planets did not orbit the earth but the sun.

Until Galileo, the theory of Copernicus was merely interesting, but now he had proof that it was true.

With the facts on his side he wrote a book about Copernicus. In it three friends argued about whether Ptolemy or Copernicus was right. One was for Copernicus one for Ptolemy and the other was making up his mind.

Galileo framed it as a dispute because the Church had told him not to teach or write about the theory of Copernicus as if it were true. But it was hardly even-handed: the defender of Ptolemy was called Simplicius.

The wrath of the Church came down on him. He was surprised: the pope was his friend and a lover of science. Galileo was a pious, sincere Christian who only wanted to guide the Church to new truths. He felt that his enemies in the universities were pulling strings.

Galileo was called before the Inquisition. He was questioned, made to confess that Copernicus was wrong and then he was silenced. He was to go to prison, but later it was agreed he could live at home but not come and go as he pleased.

He retired to his country house near Florence where he lived the rest of his days with his daughter. He never said another word about Copernicus, but there he wrote “The Two New Sciences”, laying the foundation of the new physics that would destroy Aristotle and be developed by Newton.

He died in 1642. That Christmas Newton was born.

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New York

steinberg.jpgNew York City (1613- ) is the largest city in America. From 1925 to 1965 it was the largest city in the world. It is not so much a large American city as a world city that is in America. The people in New York come from all over the world.

Where Washington is the capital of American government, New York is the capital of American business.

Among other things, New York gave the world: Santa Claus, pizza, Billie Holiday, electric power, hip hop, baseball and the New York Times.

When you live in New York it seems like the centre of the world. It is just like that Saul Steinberg cover of the New Yorker which shows everything between Ninth Avenue and China: New York takes up more than half the picture.

I do not know why, but when I walk down Fifth Avenue I feel more alive and more right in my skin than anywhere else. One time I had been away from New York for a number of years and when I came back I felt like I had grown old. There is just something about New York.

New York is in the north-east of the country on the sea, at the end of a long island. In the harbour is a tall green woman, Lady Liberty. If you come from over the sea she is the first thing you see of New York.

New York is a world unto itself and it has worlds within worlds. You will see more change and difference in one mile of New York than in 500 miles of the middle of America. You could visit every part of New York and when you were done, it will have all changed and you could do it all over again.

New York has prostitutes, madmen, killers and drunks, but most people are like those anywhere. It is true New Yorkers do not always seem nice, but it is more their manner than their hearts. They do not trust charm and want you to tell it like it is.

New York has beautiful women of every shade and colour.

In New York no one knows you. They do not know your past in wherever it was you came from. Nor do they care. This gives you the freedom to leave your past behind and start all over.

What helps is the feeling in the city that life is not ruled by fate or chance but by what you make it.

The crime in New York is not like it was. If you keep your wits about you and use some common sense, you will be safe enough.

New York is made up of five boroughs, all but the last have  a million or two each:

  • Manhattan
  • Brooklyn
  • Queens
  • The Bronx
  • Staten Island

Most New Yorkers work in Manhattan but live in one of the other boroughs – the “Outer Boroughs” – where it is cheaper to live. Manhattan is the heart of the city.

– Abagond, 2006.

Manahatta

Manhattan in 1609 and 2009.

New York in 3978.

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