How the least read book in history changed our view of the universe forever

“So when did people work out that the sun was in the middle of the solar system and the earth moved around it?”

Oh, that took a while, about two thousand years from the time that the ancient Greeks decided that everything moved around the earth.

“Two thousand years?”

Not a long time in terms of the age of the universe. It wasn't that no one had suggested an alternative. Back in the time ancient Greece, Aristarchus of Samos suggested that the earth moved around the sun around 270 BC. Even before him the ancient Indian astronomers put the sun at the centre of the universe in around 900BC. A man called Nikolaus Krebs said it in the 1400’s, but it was another hundred years before the the idea really started to catch on.

“What happened then?”

A polish astronomer called Niklaus Koppernigk published a book that changed people's view of the universe for good.

“How come I've never heard of him?”

Perhaps because people usually call him by the Latin version of his name,
Copernicus.

“I think I've heard of him. So what did he say about the universe?”

He put the Sun in the centre and then worked out a system to explain the movements of all the planets. The fancy word for this is Heliocentric and Geocentric is where the Earth is at the centre. He didn't get it exactly right but it was an important move in the right direction.

“So there must have been a big splash when he discovered that.”

Not really. Nothing happened for thirty years because he was too scared to announce it.

“Scared of what?”

The Church. At that time the Church was very powerful and totally opposed to anyone disagreeing with their view of the universe. The real problem was that he was in the Church and had the post of Canon.

“Tricky one. I can see why he looked so worried in this picture.”

So tricky that he only published his theory that placed the sun at the centre of things when he was almost on his death bed.

“So he didn’t have much time to enjoy the glory after it was published.”

True but it caused such a stir with the Church that he was probably right to wait until just before he died. Very few people actually read the book because it was banned by the Church just after its publication until 1835. By the time it could be published everyone believed the ideas anyway so no-one really bothered to read the book De Revolutionibus Orbium Coelestium which in English means On the Revolution of the Celestial Spheres. So it would probably rate as the world’s most famous and least read book.

“So how did the idea spread if the book was banned so fast?”

There is nothing like banning a book to make people seek out the few copies that were printed. One of the most important turning points was that Copernicus's ideas were taken up by greatest minds of the times, men like Galileo.

“The same man who tried to measure the speed of light with the two lamps and two assistants that you told me about earlier?”

That’s him. Galileo almost single handedly overturned the classical Greek view of the universe. Aristotle and Ptolemy represented the unquestionable truth to most people at this time. This truth required the existence of perfect, unchanging crystalline spheres, with the Earth at the centre and everything revolving in perfect circles. Galileo charged through this peaceful image of perfection like a bull in a renaissance china shop and disprove some of the most cherished ancient beliefs about the universe.

“How did he manage to do all that?”

He heard of man in Holland who had made an instrument that could far away things much clearer.

“What kind of instrument?”

A telescope. It was just a simple tube with two hand polished lenses and Galileo being good at almost everything made himself one. As soon as he did, he pointed it at the night sky. He became expert at designing telescopes and made an amazing series of discoveries about the skies above. The Greeks said the sun was this perfect glowing ball, but he discovered spots on the sun so that showed that idea was wrong. Though of course believers in the old ideas said the problem was with his telescopes.

“Was it?”

Not at all, the Sun really does have spots but that wasn't all Galileo discovered. He found that the moon had mountains and craters that cast shadows, so the moon wasn't a perfect sphere. He found that they were far more stars than can be seen with the naked eye and the milky way, the local galaxy, is in fact made up of thousands of faint stars. He also found that Jupiter had four moons revolving around it.

“Why was that important?”

Well one of the arguments that the Earth had to be at the centre was that if it were moving through space then the moon would be left behind. So when Galileo found moons around Jupiter that removed this argument, even if the Earth did stay still how could they explain how Jupiter's moons could move with it?

“But didn't they know about gravity?”

They knew things fell if you dropped them but Isaac Newton hadn't been born yet so there was no understanding that things like the moon would be affected by gravity.

“So they accepted the idea of the Sun being at the centre of the Universe then?”

Oh they didn't give up that easily. Believers in the old established ways of thinking soon invented answers for Galileo's findings, but these were a little far fetched. Ahah, they said, yes there may appear be mountains and valleys on the moon, but the valleys are filled with a pure, transparent crystal material so the moon is really a perfect sphere.

“That's a daft idea.”

People will often jump through hoops rather than change their minds. But as the new astronomy revealed ever more about the universe, the authorities adopted a different tack. They took to the pulpits and denounced the dangerous and heretical views of these renaissance madmen. Galileo was hauled up before the ecclesiastical courts and forced to renounce his dangerously mistaken views. To save his neck he stood up and declared that the Earth remained still and everything else moved.

“Why did he change his mind?”

Oh, he didn't. In true schoolboy tradition, no sooner had he said the words than he famously muttered under his breath at the end of his trial,. ‘..but it does move’.

“So what happened to him?”

Galileo was placed under house arrest for the last years of his life but that didn't stop him writing and while he was locked up at home he produced his last book - Dialogue Concerning the Two Chief World Systems. Galileo’s book was written as conversation just like this blog. After that the idea of a telling people about science with imaginary conversations fell out of fashion for five hundred years.

“So did Galileo and Copernicus get it all right, was there anything else to discover about the movements of the planets?”

No matter how much we think we know there is always more to discover. Copernicus finally made the world believe that the Earth spun on it is axis like a top and moved around the Sun, which is quite an achievement, if you watch a sunrise or sunset it is much easier to believe the sun is really rising or falling than the ground underneath you is spinning. But he didn't get it all right, he was still attached to the ancient Greek love of circles and ended up with a very complicated system. To explain the movements of the planets the ancient Greek plan needed the planets to rotate around the Earth and do little circles in space too called epicycles. Copernicus's system was just as complicated and in fact the only thing he really got right was putting the sun at the centre of the solar system.

“Who worked out how the planets moved properly then?”

A man called Johannes Kepler who was born in 1571 in Württemberg, Germany. Worked out that the planets don't move in circles but ellipses, sort of egg shaped orbits. From this he created his three laws of planetary motion even though he didn't know why these laws were true. He just worked them from studying the movements of the planets.

“So who did that bit?”

Isaac Newton. Remember his law of gravity? Well when Newton worked out gravity it turned out that his equations could be used to show why Kepler's laws were true.

“So they got it all right?”

Not even then, there was a wobble in the planet Mercury that still couldn't be completely explained.

“So who worked that one out?”

Oh, someone not a million miles from here.

“You!”

What am I? The confused life of a light particle

Remember I told you about Isaac Newton when we were talking about gravity?

“The apple man and his laws of motion. I remember him.”

Well he is just as famous for working out where the colours from a rainbow come from. He discovered that white light was made up of lots of different colours.

“How did he do that?”

Well the strange thing was that everyone in the local town market knew it already. They sold triangular bits of glass, as novelties. This is what Newton wrote in one of his books – ‘I procured me a triangular glass prism to try therewith the celebrated phenomena of colours’.

“Strange way of talking. What does that mean?”

This was how they spoke three hundred years ago. It means he bought a prism to look at the colours it makes. He worked out that raindrops must act in the same way to turn sunlight into a range of colours.

"So if everyone knew about these colours why is Newton famous rather than the person who first made these prisms?”

He did something much more important than discovering about prisms and colours, he examined it and worked out why a prism makes colours. By experimenting with these prisms Newton worked out a set of rules for how light could be split up into different colours and recombined again. He started by showing how light could be split up by a prism into different colours.

“But we knew that already”

Yes but people thought it was something magical about the glass not a feature of light. He also showed that these individual colours couldn't be split any more by passing the light through another prism. So the prism must separate light into its individual components like unravelling a rope made from lots of different coloured threads. What no-one suspected was you make white light from mixing all the colours back together again.

“Was that an important discovery? It doesn’t seem as big an issue as gravity.”

Not on a galactic scale but closer to home colour televisions use Newton’s discovery.

“Really?”

Oh yes. Go up close to an old fashioned television and you’ll see that all the colours including white are made up from coloured dots. You can’t see the individual dots on some modern televisions but every colour is still made up of a mix of three single colours. But what was much more important than television was that all this inspired Newton to produce an idea or theory about what light is.

"And the answer was?"

Newton concluded that light was made up of little particles, corpuscles as he called us, of different types. Each different type represents a different colour across the rainbow, or spectrum as scientists call it, from red to violet. White light is an equal mixture of all the different types. Every hue imaginable can be made by mixing the different types in varying proportions.

“But you said from the start that we were light particles or photons.”

I did because on this point I agreed with Newton. But for the next two hundred years, this was one thing that people thought Newton got wrong. Christiaan Huygens a Dutch man and French man Augustin Fresnel, argued that light was entirely wave-like spreading like ripples across water and most scientists started to believe that light was a wave.

“But you said near the start that we couldn’t be waves because if we were we couldn’t get through empty space.”

Very true but all that took a lot of working out and it just shows that scientists spend as much time getting things wrong as they do getting them right. The wave idea seems odd to most people because light casts shadows and so appears to always travel in straight lines. Waves on the sea spread a little around objects like boats, rocks and harbour walls. Sound waves carry sounds around corners.

“I can hear around corners but I can’t see around corners. So light and sound must be different.”

Yes, but in fact light does go around corners.

“No, it doesn’t.”

It does but only by a tiny amount and you have look carefully to see it. Just after Newton died another clever Englishman Thomas Young started investigating shadows. Although the edge of a shadow looks like a sharp line between dark and light, if you look closely you can detect faint bright lines running alongside the main light-dark line in the areas that should be dark.

"You're really telling me that light spreads a very tiny amount around corners?"

As strange as that sounds it's true. Young wasn't the first person to see strange things in shadows but he was the first to be able to explain it. In 1803 Thomas Young looked at the shadows made by shining light through two narrow slits that were very close together. In the middle of the shadow cast by the solid bar between the two slits was a faint line of light. Some of the light must have been bent around the solid edge in the same way that waves in the sea can bend around the edges of boats or harbour walls. There were also fainter lines of light, fringes, each side of this central line. All this only makes sense if light are like waves.

“It doesn’t quite make sense to me I’m afraid Albert.”

It’s a bit complicated but here is how it works. Young worked out that these fringes depend on the light from one slit ‘interfering’ with light from the other.

"What does ‘interfering’ mean?"

Interference is science-speak for where two waves collide. It doesn't matter what type of wave you are thinking about; sound waves, light waves and even waves on the ocean can all produce interference. Thomas Young worked out that the lines of light appeared where the peak of the two light waves from the two slits combined and added together. Imagine the peak of a wave hitting the two slits at the same time. At the two slits only a small amount of the wave gets through, just enough to make two smaller waves which are in exact synchrony because they are starting off at the same time. If these little waves travel the same distance then they will remain in sync with each other. So at the centre of the bar's shadow they will have travelled exactly the same distance and all the peaks of the little waves will all line up. The peak of one wave will meet the peak of the other making a wave that is twice as big. This is called constructive interference and that’s how you can get a light of light in the middle of a shadow. At all the places where this interference happens you get a fringe of light. Here is a website that shows what happens (CLICK HERE).

“So light is a wave after all.”

Well it certainly can certainly act like a wave. Young also found that different coloured lights had fringes that were different distances apart, fringes from red light being further apart than fringes from blue light. From this he worked out the light of different colours had a different wavelength.

"What's a wavelength?"

It's how long a single wave is, from the peak of one wave to the peak of the wave following immediately behind it. In the sea there might be 10 metres between waves so a sea-wave has a wavelength of 10 metres. A sound wave will have a wavelength of a bit less than a metre depending on the pitch. Young worked out from the spacing of the fringes that light had a wavelength too but it was very very small. He calculated that red light must have a wavelength of 700 billionths of a metre and blue light 400 billionths of a metre.

"How big is my wavelength?"

Tiny, about 500 billionths of a metre. You also have a frequency; if you could stay at one point and let another light wave pass you by, then the number of peaks that pass you in a second is the frequency of the wave. It also means how many times a second you are vibrating. Frequency and wavelength are related. The smaller the wavelength, the more bunched together the waves and the more waves that will go past in a second and so the higher the frequency.

"So if our wavelength is so small then our frequency must be very large."

It certainly is, our frequency is 600 trillion. In other words in our beam of light we are vibrating 600 trillion times each second. Sound waves from a note somewhere in the middle of a piano keyboard will only vibrate a few hundred times a second. Light of different frequencies and wavelengths have different colours but the whole range of colours is squeezed into a surprisingly small range of wavelengths. If you think of a piano keyboard, which only covers a fraction of the range of possible pitches of musical notes, then you could fit the whole range of visible light into just one octave or a scale of eight notes.

“But I can see millions of different colours, not just eight.”

The high frequency or long wavelength light on this keyboard would look red and be like the low pitched notes in sound terms. The short wavelength light would be blue and be like the high pitched sounds with the whole of the rainbow in between. There appears to be so many colours because the eyes is much better at detecting fine variations in light than ears are at detecting differences in the pitch of a sound, unless you are a bat of course.

"So if I made my wavelength shorter and shorter, would I get bluer and bluer then disappear completely?"

No you'd still be a photon; it's just that humans couldn't see you.

"What would I be?"

An ultraviolet photon. If you were a really short wavelength you might be an X-ray like the ones that black holes make.

"And if I got stretched into a longer and longer wavelength, what would I be then?"

An infrared photon, that's the sort of photon that carries the heat and warmth across space. And if you kept on being stretched you would change into a microwave photon, then a radio wave.

"Could I be stretched or squeezed into a sound wave?"

Never. Sound waves are just vibrations in air. Light is a completely separate breed altogether. After all no matter how much you stretched or compressed a dog, it would never become a cat.

“And all this could be worked out from looking at shadows?”

Amazing isn't it. Most importantly none of this made sense if light was just like small billiard balls travelling in straight lines.

“So are we travelling on a beam of light particles or on a beam of light waves?”

For most of the rest of our journey scientists on earth will be arguing about that with each side convinced that they are correct and the others are wrong.

"Will they have made up their minds by the time we arrive?"

Well sort of, but it won't be a clear victory for either side of the particle-wave argument.

"Why not?"

By then both sides will have conclusive proof that they were right all along. So by saying that light must be a particle and a wave at the same time they reach some sort of agreement.

“That sounds a bit weird.”

Oh, there are weirder things than that ahead of us. I’m only just getting you prepared for the really strange stuff like quantum mechanics and my theory of relativity.

If I have seen further....the nose, the moose and the telescope.

“So it wasn't really until Galileo got his hands on a telescope that anyone really understood anything about space?”

The telescope was a huge advance but one of the most famous astronomers of all time, Tycho Brahe, died in 1601, just seven years before the telescope was invented in Holland in 1608.

“What was he famous for?”

As well being the worlds best astronomer four hundred years ago, he is also famous for having a magnificent moustache and loosing part of his nose.

“That's a bit careless, how did he do that?”

He had a duel in on 29th December 1566 with a Danish nobleman by the name of Manderup Parsberg and lost the end of his nose.

“What his fighting over, some woman I suppose?”

No, would you believe it, they were fighting to settle and argument over who was the best mathematician. Tycho Brahe was probably right about being the best mathematician but his sword skills were clearly not quite so sharp.

“So he spent the rest of his life without a nose?”

No he had a new one made of silver and wax.

“That's a bit weird isn't it?”

I presume that was what you did back then when someone sliced off your nose, but Tycho was certainly an unusual character. At one stage he had pet moose that he brought along to a party at the castle of Landskrona in Sweden. The moose apparently drank so much beer it fell down the stairs and broke its leg and died shortly after. Despite these series of unfortunate events, Tycho became famous across Europe for his talent in making extraordinarily accurate astronomical records of the positions stars and planets. Remember Johannes Kepler I told you about who worked out how the planets move? Well, Kepler was Tycho's student and he used all these measurements to produce his laws of planetary motion.

“How did he make all those measurements without a telescope?”


He used his eyes along with a variety of instruments like the sextant and quadrant to help measure the position of the stars. He didn't believe in the ancient Greek view of the universe with the Earth in the centre or the new outrageous Copernican notion of the Earth moving around the Sun. It may not surprise you to know that this slightly larger than life character believed most strongly in his own theories. His theory had the Earth at the centre but the rest of the planets moving around the sun which in turn moved around the Earth. This was as close to Copernican thinking as you could get without getting excommunicated by the Church but it was also wrong. He had great faith that his young student Kepler, with his mathematical abilities, would be able to use Tycho’s own huge volumes of measurements of planetary positions to prove his own theories right. He fortunately died before Kepler showed something completely different.

“But the telescope must have changed things completely.”

It certainly did, it also helped to finally separate astronomy from astrology.

"I thought you said that astrology was all rubbish."

I did and it is, but hundreds of years ago people wanted their fortunes told just like they do today. The astronomers of the day like Tycho Brahe had to make predictions to get paid. They had become so good at predicting the movements of the planets and eclipses that ordinary people and a few kings as well, assumed they could predict anything which of course they couldn't. But just like today, as long as they were fairly vague in their predictions no-one seemed to mind if they didn't come true.

"So how did the telescope change things?"

By making astronomy into a science. A lot of famous names we've already met designed new types of telescopes, like Johannes Kepler and Isaac Newton. Newton developed a totally new type of telescope based on mirrors rather than lenses and the biggest light telescopes today use mirrors to collect and focus light. As bigger and better telescopes helped astronomers see fainter and more distant objects, the size of the known universe steadily grew.

“So how far away can we see now with the best telescopes.”

With telescopes like the Hubble space telescope, galaxies have been seen that are up to 13 billion light years away. The light from these galaxies has been travelling for so long that some of these light beams started their journey just 700 million years after the universe was formed in the big bang, . From these distant galaxies we can look into the past and tell what the universe was like when it was very young.

“So you can see into the past with telescopes, but not into the future.”

Exactly and deeper into space. In just four hundred years mankind's understanding of the universe has stretched from the solar system to galaxies billions of light years away. Isaac Newton once said, 'If I have seen further, it is by standing on the shoulders of giants', but you could change that to say 'If man has seen further, it is because Newton developed the reflecting telescope.'