Pioneers Of Astronomy

THE PIONEERS OF ASTRONOMY

(Image from kidsastronomy.com

(Author’s note: The following is an excerpt from an essay on the history of science that I once wrote for personal pleasure. If this excerpt proves popular I might publish some more, eventually taking us up to modern cosmological concepts like the Big Bang.)

INTRODUCTION

According to a famous story, Isaac Newton discovered gravity when an apple fell from a tree and hit him on the head. This story is almost certainly untrue, but it does highlight the way in which science progresses according to popular imagination. It is thought that, on rare occasions, a man or woman possessing an extraordinary mind has a flash of inspiration that revolutionises scientific thinking. The Earth moves! Man evolved from apes! Because these people are so obviously gifted, it often makes for amusing reading to recall how their genius was not recognised early on. Albert Einstein’s geography teacher wrote in a report that the future Nobel Prize-winning physicist would amount to nothing. Charles Darwin’s father thought his son would pursue a life of idle pleasure and bring disappointment to the family. Why did these people get it so wrong?

The reason is simple. It is because the idea of a genius revolutionising science is largely a myth. Yes, exceptional minds have left their mark, but it is more often a case that ordinary people who were in the right place at the right time are the ones who take the next step. This may happen because a new technology emerges that clearly shows a flaw in the established way of thinking. If you were told that the Moon was a flawless sphere and you trained a telescope on it, you would see that it is actually a battered rock scarred with craters. Someone had to be the first to do this, and it happened to be Gallileo. At other times, information may be gathered over the generations that points to a new way of thinking and eventually somebody notices the connections that others were missing. It is merely an accident of history that certain names have become so famous. If Einstein or Darwin had never been born the course of history would not have altered that much. Somebody else would have discovered what they did. You see, scientific progresses is rarely revolutionary, but is instead a step by step process in which one generation builds on the work of previous generations.

We can clearly see this when we chart the rise of modern science and how our of the universe changed from a mystic cosmos with our world at its centre, to a mechanistic universe in which natural laws compel the Earth to orbit the Sun. Modern science began its slow development during the 16th century, when doubts began to seep in concerning the teachings of the Ancient Greeks. Today, an idea is considered to be scientific only if one could conduct an experiment that strengthens or refutes the premise. So, if you have an idea that a seed could germinate even after being soaked in salt water for long periods, you would soak a seed in a briny solution and then see if it grows into a plant. Charles Darwin conducted just such an experiment in order to bolster his claim that seeds could drift along on ocean currents and colonise new islands. It does seem a very obvious way of proving a theory, but the scientific method took literally centuries to catch on. Preceding this were generations of thinkers who developed mental pictures of the universe, coloured by their beliefs.

PTOLEMY

(Image from turtledove.wikia.com)

The model of the universe that existed before the 16th century could trace its roots back to Ancient Greece. It had been developed by Ptolemy, who lived in the second century AD and raised in Egypt. His work drew upon 500 years of teaching and was known in his day simply as ‘The Mathematical Compilation’. But by the 16th century it had become known by its Arabic title ‘The Almagest’ or ‘The Greatest’. This neatly sums up how the likes of Aristotle or Euclid were viewed at the time. Their texts seemed to be the results of minds above and beyond mere mortals and the great structures like the Acropolis had been built using techniques that had long been forgotten. This reinforced the inferiority complex that lasted until the Renaissance.

Ptolemy’s model of the universe consisted of several crystal spheres that each contained a heavenly body. The outermost sphere contained the stars, and within this sphere was another that contained Saturn. Inside that was one that held Jupiter and so it went on until we reach the innermost sphere (the centre of the universe) containing the Earth. Everything orbited our world- the Sun, the Moon, all the planets thought to exist at that time and even the stars. Other important aspects of this model were that the planets were considered to orbit the Earth in perfect circles. That they considered the orbit of the planets to be circular had much to do with their obsession with geometry. To the Ancient Greeks, a circle was a sign of perfection so naturally the mystic universe was thought to adhere to such aesthetic qualities.

(Image from Wikipedia)

But there was a problem with this mental picture. Observing the physical universe revealed things that were hard to reconcile with the idea that everything in the universe orbited the Earth. The only way Ptolemy could make his system work was via a complex model in which the orbits were offset. He claimed that there were circles within circles and it was these so-called equals points that orbited the Earth. As far back as the 3rd century BC, beginning with Aristarchus, some radical thinkers had suggested placing the Sun at the centre of the universe. But such an idea was seemingly refuted with common sense (fear of persecution had nothing to do with the rejection of the geocentric model until the 16th century). Forget about what you know about modern astrophysics and ask yourself if you can feel any movement, any sensation of hurtling through space as the Earth follows its orbit around the sun. When you travel via car and the window is down, you feel the wind rushing past but there are days when things are very calm and still. And whereas we enjoy relatively smooth rides thanks to suspension and dampers and things like that, travel was a rather bone-shaking experience for ancient people. It seemed reasonable, then, that if the Earth itself were moving things would get very shaky indeed!

There was a lesson to be learned that is still applicable today, which is that common sense is ill equipped to understand the true nature of reality. There is a simple reason for this, which is that common sense evolved to appreciate the habitat in which it developed, and that habitat is highly unusual as the universe goes. Our senses are just not adapted to understand the totality of existence, and so it takes a person who is willing to abandon common sense to really get to grips with our place in the grand scheme of things. One such person was Nicholas Copernicus.

COPERNICUS

(Image from Wikipedia)

Copernicus was born in the Polish town of Torun on 14th February 1473 and was then known as Mikolaj Copernick. He developed an interest in astronomy during his education at the University of Kraków which he joined in 1491 and he later studied law and medicine. It was an interest in the humanist movement that lead him to Latinise his name, and it was a book about the Ptolemaic model of the universe that provided the means by which his name would be remembered centuries after his death. That book was called ‘The Epitome’ and it had a rather long gestation period. Originally, the inspiration for it came from the mind of a German called George Peurbach, who wanted to update Ptolemy’s work. This task took longer than his lifespan and so the baton was passed to a pupil of his. This person was christened Johannes Mueller but he changed it to Regiomontanus, which was a latinised version of his birthplace. Regiomontanus published the book in 1476. It included commentary on Ptolemy’s observations, more modern astronomical observations and, most importantly, it showed that there were aspects of the universe that did not agree with the model. The most striking of these was that, according to Ptolemy’s model, the orbit of the Moon should bring it closer to the Earth at certain periods. If this was really the case, shouldn’t the moon appear closer in the sky at those times? There were other mysteries as well. Why was it that the planets Mars, Jupiter and Saturn were visible all through the night but Venus and Mercury could only be seen around dawn and dusk? This is a good example of how science evolves, with one generation of thinkers providing the stepping stone to a new level of understanding. All it takes is for somebody to be willing to take that step and in this instance it happened to be Copernicus. Perhaps, he argued, Aristarchus was right after all. Maybe the sun is at the centre of the universe?

These ideas found their way into print in the form of a pamphlet called the ‘Commentariolus’ (‘Little Commentary’) of which only a few were printed and handed out to close friends in 1510. A proper book (‘De Revolutionibus Orbium Coelestium’ or ‘On the Revolution of the Celestial Spheres’) would not appear until 1543. This delay could be attributed to the fact that Copernicus was busy with other duties but also because he knew his solution to the Ptolemaic model produced its own peculiarities. Although Copernicus had taken what seems like a step in the right direction by placing the Sun at the centre of the universe, he was still very much a thinker in the mould of Ptolemy. The reason he placed the Sun and the Earth where he did was because it seemed like a pleasing mathematical picture to him. On the puzzle of why Mercury and Venus should behave so differently, Copernicus’s model explained this by showing these planets are closer to the Sun than the Earth, while Mars, Jupiter and Saturn are outside the orbit of our planet. But aside from arguing that the Earth orbited the Sun and not the other way around, Copernicus’s model was not that far removed from its predecessor. It still included crystal spheres to house the celestial bodies, and those celestial bodies still orbited in perfect circles. Because Copernicus stuck with the idea of perfect circles, his model still required equation points to hold everything together. This latter point was particularly troublesome, because Copernicus knew equation points were a way of deviating from perfect circular motion while at the same time pretending it still applied.

Another puzzle thrown up by Copernicus’ ideas had something to do with the stars. At the time the book was written, it was believed the edge of the universe (that is, the crystal sphere containing the stars) was not much further away than Saturn, which was the most distant planet that anyone of that period knew about. When travelling in a car the world outside seems to be moving and the further away things are the slower they move. This effect is called parallax. The puzzle of Copernicus’ model was that the stars did not appear to move at all. If the Earth really was travelling through space but no parallax effect could be observed in the apparent position of the stars, the only explanation was that the gap between the outermost planet and the stars was hundreds of times bigger than had been supposed. If Copernicus had pursued this idea, it would have been an even more remarkable achievement than claiming the Sun was at the centre of the universe (particularly as today we know that it isn’t.) But it seems he found it too hard to accept. Remember, that in Copernicus’ day humanity was thought to be the focus of the universe and that the stars influenced everyday concerns. It made no sense for God to put such a huge gap between Man and the stars. Copernicus died on the year his book was published and the puzzle of the stars was taken up by someone whose father provided the technological means to see further than all previous generations had been able to see.

LEONARD AND THOMAS DIGGES

(Image from strangehistory.net)

You probably know this vital tool of astronomy. It’s called the telescope. The most famous user of this instrument is probably Galileo, but it's inventor is less of a household name. Leonard Digges was born in 1520 and was educated at Oxford University. He became a well-respected mathematician and surveyor and he published several books, the first of which came out ten years after Copernicus’ book and was called ‘A General Prognostication’. This book was successful in the sense that it became a bestseller, but the ideas contained within were all based on the already out of date Ptolemaic system. However, Leonard Digges had a longer-lasting legacy in some of his inventions. He invented the theodolite around 1551 and also invented the telescope at much the same time. A good reason why he never popularised his invention was because in 1554 the Protestant Sir Thomas Wyatt lead a rebellion against the Catholic Queen Mary, who ascended the throne in 1553 after the death of Henry VIII. Leonard took part in this revolution and forfeited all his estates as a result. (He actually got off lightly since he had a death sentence commute.) Leonard Digges died in 1559, never having regained his estates.

At this point, the story turns to Leonard’s son, Thomas. It is not known when he was born, but he was roughly thirteen years old when his father died. The teenager was raised by his guardian, a man called John Dee whose wide-ranging studies included alchemy, philosophy and who was also astrologer to Queen Elizabeth I. There is a strong possibility that Dee was an early enthusiast of the Copernican model, and if his interests were not fruitful enough pickings for Thomas Digges’ mind, he also had a private collection of over a thousand manuscripts that the boy eagerly read. Thomas Digges published his first book in 1571. Actually, it was a posthumous work of his father’s called ‘Pantometria’. This was the first time that the telescope was discussed in public and one has to wonder what the impact would have been to learn of the existence of a device that “seven miles off declared what had been doone in that instant in private places”. 

But it was in 1576 that he published his most significant work. This was a greatly revised and updated version of his father’s first book and he called it ‘Prognostication Everlasting’. It was important for several reasons. For one, this was the first time that the Copernican model was discussed in detail and Digges even took the step of writing the book in English rather than Latin. Secondly, Thomas Digges made the astonishing claim that the Universe was infinite in size. It is not known exactly how he came to this conclusion, but a compelling argument can be made that he saw a multitude of stars through his father’s invention. Thomas Digges was almost the first populariser of science (after his father) but he did not devote his life to it and he never pursued the ideas in his book. He died in 1595 at a time when the Catholic Church was turning against the Copernican model…..

An essay such as this cannot be written without relying on the hard work of prior writers who have recorded important information like dates and names. My reference was an excellent book by John Gribbin called 'Science: A History'.