Archive for the ‘scientists’ Category

The following is based on part seven of Jacob Bronowski’s BBC series on the history of science and invention, “The Ascent of Man” (1973). This part is about the physics of Newton and Einstein:

Newton was born on Christmas Day in the year that Galileo died, 1642.  He got his university degree at Trinity College, Cambridge  but then came the plague years: 1665 and 1666. He went to live with his mother in the country. There he made his great discoveries in physics and mathematics.

From his notebooks we know that he was badly taught: he had to work out mathematics for himself. But along the way he discovered a new form of mathematics: calculus. It became his secret weapon.

Copernicus and Kepler told us how the planets move but could not say why. Newton could: gravity. With his law of gravity he could work out how fast an apple fell from a tree and how many days it took the moon to go round the earth. Utterly amazing.

But none of it was made public till 20 years later. In the meantime Newton made his name in optics: he showed how white light is made out of coloured light. He became a professor at Cambridge and a leading light of science in Britain.

Then one day Edmund Halley came to Cambridge to ask Newton a question about physics. Halley loved his answer but then asked, “How do you know?” Newton said he would send him the proof. That proof took three years and was so long it became a book: the “Principia” (1687). It laid out his physics. Our idea that there are laws of nature comes from that book.

Newton’s physics was a wonder of the age, yet it assumed that time and space are absolute, that they are the same for all observers. Still it stood for 200 years. Then in 1881 Michaelson found the first hole in it: light always went at the same speed no matter what. No one knew what to make of it until Albert Einstein came up with his theory of special relativity in 1905.

Einstein would think about stuff like this: Suppose you get on the tram at the town clock to go to work and your tram went the speed of light. What would you see? If you looked back at the clock you would see that time had stopped – and yet for the people on the street the hands of the clock are still moving! Strange. That means the closer you get to the speed of light, the more time slows down. Time is not absolute. Nor is space: if you push the example further you find that the tops of the buildings will look like they are bending over the street and passers-by will look tall and thin.

Einstein worked out his physics along those lines and, while his conclusions were strange, he was proved right in the course of his life. Even the bit about the edge of a phonograph record ageing more slowly than the centre.

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Sir Humphry Davy (1778-1829) was a British scientist who discovered the elements potassium, sodium, barium, strontium, calcium and magnesium. He also discovered laughing gas, proved that iodine was an element and that diamonds are just a form of carbon.

But his greatest discovery was a man: Faraday, one of the greatest scientists of all time.

Davy’s big trick, the reason he discovered so many elements, was that he built the world’s biggest battery. That is why he could discover so many elements. With the electricity that it created he passed it through different substances to break them down into simpler ones. Some of these simpler substances were elements that no one had ever seen before.

For example, he thought potash had some kind of metal in it. He passed his electric current through the stuff and out came little shining balls of metal. He called the metal potassium.

Guy-Lussac was doing the same sort of thing in France. In one case he beat out Davy, finding boron nine weeks before he did.

When Davy was young he studied medicine and wanted to be a poet. He loved to fish and walk through the woods and look at the mountains. In one pocket he had his fishing hooks and in the other he had stones that he found along the way.

As a poet Davy was friends with Wordsworth, Coleridge and Southey, some of the best British poets of the time.

But he was not to become a famous poet: at age 19 he read Lavoisier’s book on chemistry. It hooked him for life. A friend of Davy’s let him use his library and chemistry laboratory, one of the best in England as it turned out.

Davy started out by trying to understand out how batteries work. Once he understood that he saw they could be used to break down substances into simpler ones.

Davy came to London. It turned out that he was a great speaker, even though his Cornish English sounded strange. The women liked his handsome looks. His talks on chemistry made him famous and helped to give science a good name. One person who came to see him was Faraday. Davy later hired him.

Davy did not believe in Dalton’s atoms. We take them for granted now, but it was a new idea then, one that was slow to catch on.

Davy was not all that careful: sometimes things blew up, one time he almost went blind.

He made a habit of breathing in any gas he created. He wanted to learn as much as possible about it. Once this paid off when he discovered laughing gas. Another time it almost killed him. But over the years it destroyed his health. He only lived to be 50.

One of the best things he did was to make mines safer with his invention of the safety lamp. He worked out a way for the lamp’s flame to burn without being in danger of blowing up inside the mine.

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John Dalton (1766-1844) was a British scientist who proved that ordinary matter is made up of atoms. It is an old idea that goes back to Democritus and the ancient Greeks. Many believed it to be true, but no one could prove it till Dalton.

The idea is this: take anything and cut it in half. Then cut it in half again and so on. Sooner or later you will get to a piece of it that you cannot cut no matter what. It is not a question of how good your cutting instrument is: the thing you are cutting has to be made of something, however small it might be. If you could go on cutting forever that would mean it was made of nothing, which is impossible.

Those small little bits that the thing is made out of, the bits you cannot cut no matter what, were called atoms by Democritus. Atom is Greek for “uncuttable“.

What Dalton called atoms are cuttable, as it turns out, but no one knew that for a hundred years, so the name stuck.

For a piece of bread, by the way, you would get to the level of Dalton’s atoms after cutting it in half about 80 times.

The Greeks thought atoms were different shapes: water atoms were round, fire atoms were sharp, etc. Dalton said atoms were all alike except for their weight. All gold atoms, for example, have the same weight and no other atom has that weight. It is how you tell them apart. That is what made Dalton’s atoms new and different. And provable.

Dalton noticed that when oxygen and hydrogen are put together to make water, the oxygen that goes to make up the water always has a weight eight times greater than the hydrogen.

And it was not just water. All the substances that scientists knew how to make back then out of elements were the same way. The weights were always the same for a given substance and the numbers were always small and simple, like 3 to 8 or 6 to 1.

Nothing made sense of this but Dalton’s atoms with their different weights. But it took a while for the idea to firmly take hold.

Earlier Dalton had studied the weather and wrote one of the first books about it. He made his own instruments and, like Benjamin Franklin, recorded the weather every day for nearly 60 years.

From studying the weather he became interested in the nature of air. That brought him to the work of Boyle, which in turn brought him to chemistry at age 30. Seven years later, in 1803, he came out with his ideas about atoms. The book followed in 1808.

Most groundbreaking ideas like that come to people when they are in their middle to late 20s, not their late 30s. But Dalton’s case shows that it is not age that matters but how long you have been in the field.

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Antoine Lavoisier (1743-1794) was a French taxman and scientist. He did for chemistry what Galileo did for physics: he made it a hard science by putting ideas to the test with hard numbers.

By the 1700s chemistry had come a long ways from the days when it was called alchemy and men tried to turn lead into gold. But it was still not a proper science. Lavoisier made it one.

Lavoisier loved school as a child. When he grew up he gathered taxes for the king. He was not the one who knocked on your door, he was higher up than that. But everyone knew who he was and knew how he got so rich. He married a beautiful 14-year-old girl.

With his riches he built an amazing laboratory where he worked on his chemistry with the help of his wife. Jefferson, Franklin and Priestley and other leading lights of science visited him there.

But more important than his beautiful laboratory or his beautiful wife was his approach to chemistry:

  1. An element is any substance that cannot be broken down into simpler substances. Lavoisier listed 32 of them.
  2. Every substance is itself an element or made up of elements.
  3. A chemical reaction is when one substance changes into another. This comes from a change in the number or proportion of the elements that make up the substance.
  4. The conservation of matter: matter is neither created nor destroyed – it just becomes a different sort of substance.
  5. Measure the weight of everything that goes into a chemical reaction and everything that comes out of it, even the air.

Much of this is now common sense, but it was not in the 1700s. It was Lavoisier who made it so.

With this approach Lavoisier was able to tell which ideas were true and which were false.

One of these false ideas was phlogiston. For over a hundred years science said that things burned because they had phlogiston. Wood is full of phlogiston, which is why it burns so easily. The ash that is left over after the wood is burned has no phlogiston. It has been all used up. That is why you cannot burn ashes.

Lavoisier disproved phlogiston. He heated different kinds of metal inside closed containers until they started to burn and change. When he measured the weight of the containers before and after, there was no change. But the burned metal was now heavier. Instead of losing phlogiston, whatever that is, something from the air must have been added to the metal.

For most this put an end to the idea of phlogiston.

In 1789 he came out with his “Elements of Chemistry”, one of the great works of science.

But that year the king was overthrown and the country went mad, wanting to kill all the king’s men. Lavoisier was one of the king’s men. In 1794 they sent him to the guillotine and cut off his head.

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Joseph Priestley (1733-1804), a British scientist, discovered oxygen. He was the first to make and drink soda water, which soft drinks are now made from, and the first to call that stuff that comes from inside trees in South America “rubber” (because he rubbed out pencil marks with it).

He was a friend of Benjamin Franklin and later moved to America where spent the last ten years of his life. There he became friends with Thomas Jefferson.

The Americans claim him as one of their own and France made him a citizen, but he did all his best work while still in Britain.

He favoured both the Americans and the French in overthrowing their kings. This made him hated in Britain, which still believed in kings. His house was burned down once. He was very forgiving about the whole thing, but thought it best to spend his old age in America.

As part of the Lunar Society, which met on the night of the full moon, he knew James Watt and Erasmus Darwin, grandfather of Charles Darwin. He also belonged to the French Academy of Sciences even before he discovered oxygen.

He discovered oxygen in 1775. He was not the first: as he later found out, Scheele in Germany had beat him by a few months. But Priestley gets the credit because he made it public first.

He made oxygen by burning mercury till it turned into a red powder and then heated the powder till it turned back into mercury. The stuff that came out of the red powder into the air made wood burn brighter and made mice move and jump more. He found out the same stuff was coming from plants.

Priestley thought that breathing oxygen would become a fashionable vice among the rich.

Priestley did not call it oxygen, a name we get from Lavoisier. He called it dephlogisticated air because it had no phlogiston.

For over a hundred years science said that things burned because they had phlogiston. Wood is full of phlogiston, so it burns easily. Dephlogisticated air, said Priestley, lacked phlogiston and so took it up readily from things that were burning. This made them burn more strongly.

Priestley did not make a living from science. No one did before the late 1800s when German universities started hiring scientists. Science was just something he did on the side. He worked as a Unitarian minister.

Unitarians are Christians who do not believe in the Holy Trinity. They follow the teachings of Jesus but do not think he is divine. It was the latest thinking in those days and some thought that America would become Unitarian by 1900.

It suited Priestley who thought for himself and was up on all the newest ideas.

Priestley never studied science at university: he studied philosophy and languages. He knew Hebrew and Arabic. It was Benjamin Franklin who later got him interested in science. Franklin was in Britain trying to prevent the coming war between America and Britain.

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Sir William Herschel (1738-1822) was a German-born British scientist who discovered Uranus, the first planet discovered since ancient times. He also discovered two moons of Uranus (Oberon and Titania) and two moons of Saturn (Mimas and Enceladus).

We take new discoveries in science for granted. We expect to read about a new one every few months in the newspaper. But in the 1700s people thought Newton was the last word in science, that everything had been discovered already. Uranus was a breath of fresh air.

Herschel was the greatest astronomer of his day. He became that by making the best telescopes in the world and studying every single part of the night sky with them, not knowing what he would find there.

He came to England from Germany at age 19, not wanting to fight in the German wars, even though his father was in the army. Instead he taught music in the English town of Bath.

He taught himself Latin and Italian and read Newton’s book on optics, about how glass lenses bend light. He started making lenses of his own and then, in the 1770s, telescopes. He brought over his sister Caroline from Germany and she helped him.

One by one he looked at each star in the sky with his telescope. Then in 1781 he came upon a star that was not a star. It was a small little circle of light.

At first he thought it was a comet, but when he and Laplace worked out its orbit, they found out it circled the sun beyond Saturn. It was a planet like Saturn!

You can see it with the naked eye if you know where to look. It looks like a very faint star and had been appearing on star maps, but it moved so slowly no one knew it was a planet. Not till Herschel.

He named it George’s Star, after the king. Others called it Herschel. Someone else named it Uranus, after Saturn’s father. That is the name that caught on.

Herschel thought there was life on the other planets, even on the sun. He did not think the sun was a huge ball of fire like we do: he thought its clouds were on fire, that sunspots were holes through the clouds where you could see a world below.

He tried to find out how far away the stars were but had no luck. But he did find out that the sun is moving among the stars. It is headed for the constellation of Hercules.

He also found out that the sun is in a huge wheel made of stars, what we now call the Milky Way Galaxy. He saw other such wheels of stars through his telescope, other galaxies, very far away.

Uranus takes 84 years to go round the sun. When it returned to the place where it was when Herschel was born, he died.

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Tycho Brahe (1546-1601), a Danish nobleman, was one of the greatest astronomers of all time. Before Tycho’s time only Hipparchus was better. Tycho tried to prove Copernicus wrong but his work, continued by Kepler after his death, only proved Copernicus right once and for all.

Copernicus said that the planets went round the sun. Ptolemy said they went round the earth. Tycho said something in between: yes, the planets went round the sun, but the sun went round the earth!

Tycho turned to astronomy when he saw an eclipse while at university. He once got in a fight there in the middle of the night over a point of mathematics. He lost his nose and later got a metal nose made to put in its place.

Although he was a nobleman who was often full of himself, he did fall in love with a simple country girl and married her.

In the universities they taught Aristotle: the earth was the centre of the world, a place of endless change, but the heavens above the moon were perfect and unchanging. What about comets? Aristotle said they were below the moon, part of the earth’s weather.

Tycho proved the heavens were anything but unchanging. He became famous when he found a new star that was not there before. It was called Tycho’s star (we call it a nova). It soon became brightest star in the sky.

Tycho also proved that comets were not part of the weather but farther than the moon. By gathering observations from different parts of Europe he could tell that its position in the sky against the stars changed less than the moon’s, meaning it was farther away.

The king built an observatory for Tycho on the island of Ven in between Denmark and Sweden. There Tycho studied the stars with the best instruments in the world. He carefully recorded the motion of the sun and the planets. His measurements were five times better than anything ever made. He even took into account the effects of the air and the limits of his own instruments. He wanted to prove Copernicus wrong.

Tycho wrote a letter to Galileo and told him that if Copernicus were right, then we should be able to measure how far away the stars were. Galileo had no answer for that. What neither of them knew was how unimaginably far away the stars were.

When the king died Tycho had to leave the island. He travelled to Prague. There he met Kepler. Kepler knew what a gold mine Tycho’s tables of numbers were. He promised Tycho to continue his work after he died and prove Copernicus wrong once and for all.

Kepler did continue his work, but in the end he had to admit that Copernicus, with a few changes, was right after all.

Later in the 1600s Tycho’s old observatory was burned down by war. Riccioli, who named the craters of the moon, named the brightest one Tycho in his honour.

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