Archive for History

A Potted Prehistory of Cosmology

Posted in History, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , , , on January 26, 2012 by telescoper

A few years ago I was asked to provide a short description of the history of cosmology, from the dawn of civilisation up to the establishment of the Big Bang model, in less than 1200 words. This is what I came up with. Who and what have I left out that you would have included?

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 Is the Universe infinite? What is it made of? Has it been around forever?  Will it all come to an end? Since prehistoric times, humans have sought to build some kind of conceptual framework for answering questions such as these. The first such theories were myths. But however naïve or meaningless they may seem to us now, these speculations demonstrate the importance that we as a species have always attached to thinking about life, the Universe and everything.

Cosmology began to emerge as a recognisable scientific discipline with the Greeks, notably Thales (625-547 BC) and Anaximander (610-540 BC). The word itself is derived from the Greek “cosmos”, meaning the world as an ordered system or whole. In Greek, the opposite of “cosmos” is “chaos”. The Pythagoreans of the 6th century BC regarded numbers and geometry as the basis of all natural things. The advent of mathematical reasoning, and the idea that one can learn about the physical world using logic and reason marked the beginning of the scientific era. Plato (427-348 BC) expounded a complete account of the creation of the Universe, in which a divine Demiurge creates, in the physical world, imperfect representations of the structures of pure being that exist only in the world of ideas. The physical world is subject to change, whereas the world of ideas is eternal and immutable. Aristotle (384-322 BC), a pupil of Plato, built on these ideas to present a picture of the world in which the distant stars and planets execute perfect circular motions, circles being a manifestation of “divine” geometry. Aristotle’s Universe is a sphere centred on the Earth. The part of this sphere that extends as far as the Moon is the domain of change, the imperfect reality of Plato, but beyond this the heavenly bodies execute their idealised circular motions. This view of the Universe was to dominate western European thought throughout the Middle Ages, but its perfect circular motions did not match the growing quantities of astronomical data being gathered by the Greeks from the astronomical archives made by the Babylonians and Egyptians. Although Aristotle had emphasised the possibility of learning about the Universe by observation as well as pure thought, it was not until Ptolemy’s Almagest, compiled in the 2nd Century AD, that a complete mathematical model for the Universe was assembled that agreed with all the data available.

Much of the knowledge acquired by the Greeks was lost to Christian culture during the dark ages, but it survived in the Islamic world. As a result, cosmological thinking during the Middle Ages of Europe was rather backward. Thomas Aquinas (1225-74) seized on Aristotle’s ideas, which were available in Latin translation at the time while the Almagest was not, to forge a synthesis of pagan cosmology with Christian theology which was to dominated Western thought until the 16th and 17th centuries.

The dismantling of the Aristotelian world view is usually credited to Nicolaus Copernicus (1473-1543).  Ptolemy’s Almagest  was a complete theory, but it involved applying a different mathematical formula for the motion of each planet and therefore did not really represent an overall unifying system. In a sense, it described the phenomena of heavenly motion but did not explain them. Copernicus wanted to derive a single universal theory that treated everything on the same footing. He achieved this only partially, but did succeed in displacing the Earth from the centre of the scheme of things. It was not until Johannes Kepler (1571-1630) that a completely successful demolition of the Aristotelian system was achieved. Driven by the need to explain the highly accurate observations of planetary motion made by Tycho Brahe (1546-1601), Kepler replaced Aristotle’s divine circular orbits with more mundane ellipses.

The next great development on the road to modern cosmological thinking was the arrival on the scene of Isaac Newton (1642-1727). Newton was able to show, in his monumental Principia (1687), that the elliptical motions devised by Kepler were the natural outcome of a universal law of gravitation. Newton therefore re-established a kind of Platonic level on reality, the idealised world of universal laws of motion. The Universe, in Newton’s picture, behaves as a giant machine, enacting the regular motions demanded by the divine Creator and both time and space are absolute manifestations of an internal and omnipresent God.

Newton’s ideas dominated scientific thinking until the beginning of the 20th century, but by the 19th century the cosmic machine had developed imperfections. The mechanistic world-view had emerged alongside the first stirrings of technology. During the subsequent Industrial Revolution scientists had become preoccupied with the theory of engines and heat. These laws of thermodynamics had shown that no engine could work perfectly forever without running down. In this time there arose a widespread belief in the “Heat Death of the Universe”, the idea that the cosmos as a whole would eventually fizzle out just as a bouncing ball gradually dissipates its energy and comes to rest.

Another spanner was thrown into the works of Newton’s cosmic engine by Heinrich Olbers (1758-1840), who formulated in 1826 a paradox that still bears his name, although it was discussed by many before him, including Kepler. Olbers’ Paradox emerges from considering why the night sky is dark. In an infinite and unchanging Universe, every line of sight from an observer should hit a star, in much the same way as a line of sight through an infinite forest will eventually hit a tree. The consequence of this is that the night sky should be as bright as a typical star. The observed darkness at night is sufficient to prove the Universe cannot both infinite and eternal.

Whether the Universe is infinite or not, the part of it accessible to rational explanation has steadily increased. For Aristotle, the Moon’s orbit (a mere 400,000 km) marked a fundamental barrier, to Copernicus and Kepler the limit was the edge of the Solar System (billions of kilometres away). In the 18th and 19th centuries, it was being suggested that the Milky Way (a structure now known to be at least a billion times larger than the Solar System) to be was the entire Universe. Now it is known, thanks largely to Edwin Hubble (1889-1953), that the Milky Way is only one among hundreds of billions of similar galaxies.

The modern era of cosmology began in the early years of the 20th century, with a complete re-write of the laws of Nature. Albert Einstein (1879-1955) introduced the principle of relativity in 1905 and thus demolished Newton’s conception of space and time. Later, his general theory of relativity, also supplanted Newton’s law of universal gravitation. The first great works on relativistic cosmology by Alexander Friedmann (1888-1925), George Lemaître (1894-1966) and Wilhem de Sitter (1872-1934) formulated a new and complex language for the mathematical description of the Universe.

But while these conceptual developments paved the way, the final steps towards the modern era were taken by observers, not theorists. In 1929, Edwin Hubble, who had only recently shown that the Universe contained many galaxies like the Milky way, published the observations that led to the realisation that our Universe is expanding. That left the field open for two rival theories, one (“The Steady State”, with no beginning and no end)  in which matter is continuously created to fill in the gaps caused by the cosmic expansion and the other in which the whole shebang was created, in one go, in a primordial fireball we now call the Big Bang.

Eventually, in 1965, Arno Penzias and Robert  Wilson discovered the cosmic microwave background radiation, proof (or as near to proof as you’re likely to see) that our Universe began in a  Big Bang…

The Knife Man

Posted in History, Literature with tags , , , , , , , , , , , on July 9, 2011 by telescoper

It looks set to be the proverbial wet weekend here in Cardiff and I’m waiting for a pause in the rain before going out to do my Saturday shopping. Having done the crossword already, I should be cleaning the house but instead I thought I’d post a quick comment about the fascinating book I’ve just finished reading.

The Knife Man, by Wendy Moore, is an account of “The Extraordinary Life and Times of John Hunter, Father of Modern Surgery”. It’s a measure of my ignorance about medical history that I didn’t even know who John Hunter was when I started reading this, although I had heard of the Hunterian Museum without realising who it was named after.

I won’t give a lengthy account of Hunter’s biography; that’s done very well elsewhere on the net and indeed in the book, which I thoroughly recommend. It is worth emphasizing, however, what a remarkable man he was. Born in Scotland in 1728, he didn’t go to University and received no formal medical training. He went to London in 1748 in order to become assistant to his brother William, a noted surgeon at the time. John’s primary rsponsibility was to help with the dissection of human cadavers during William’s anatomy classes. He soon became fascinated by anatomy and himself became extremely adept at dissection. He received some medical training in London, had a spell as an army surgeon and eventually set up a private medical practice in London at which he ran his own anatomy classes for paying students. He became one of the top surgeons in London and attended to the needs of many prominent Georgian figures, including King George III.

But, as impressive as it was, his medical career wasn’t the most remarkable thing about Hunter’s life. His interests extended far beyond human anatomy and from an early age he was an avid collector of all sorts of animals, alive and dead. As he became wealthier through his medical practice and lectures he spent increasing amounts of cash on acquiring rare specimens, which he usually dissected in order to understand them better. He also collected specimens of diseased human organs, bones, and fossils. There was a very dark side to this work too. The grisly business of acquiring fresh human human corpses led him to make connections with graverobbers. Worse, he also experimented on human specimens, usually members of London’s poor. He did pay them for their pains, but that’s hardly the point.

Hunter’s studies led him to conclude – years before Darwin – that species were not fixed and immutable but that animal populations altered over time, with some creatures becoming extinct. Although he doesn’t seem to have used the word “evolution”, his work in this area was certainly heading in that direction. He was made a Fellow of the Royal Society in 1767.

Above all I think what stands out about Hunter was that he pioneered the use of the scientific method in the field of medicine. His lack of formal training meant that he wasn’t steeped in the dogma or orthodox medicine which had led to many bizarre and/or dangerous practices. One wonders what chain of reasoning had led doctors to suppose that pumping tobacco smoke into a patient’s anus using specially constructed bellows could possibly have any therapeutic value!

Hunter learned primarily from experience. He knew, for example, that major surgery in Georgian times was very likely to kill the patient. There were no anaesthetics, so death by shock was a strong possibility. Loss of blood was a danger, too, unless the operation was completed extremely quickly. Moreover, doctors at the time – Hunter included – had no idea about how infections were spread and surgeons would often operate with instruments encrusted with the blood of previous victim. In the (unlikely) event of a patient surviving the agony of, say, an amputation, they would probably die of  some form of infection within a few days anyway. Hunter’s policy in the light of all this was to refuse to operate unless the situation was truly desperate.

For example, when Hunter was an army surgeon, the prevailing attitude to gunshot wounds was that the bullet had to be removed at all costs. Moreover, it was believed that gunpowder was poisonous, so entry wounds were usually “enlarged” to remove tissue that had been blackened or burnt. One day, a group of British soldiers had come under fire and several had been badly injured. They escaped the ambush and holed up in a farmhouse, where they were found a few days later. One had two bullets in his thigh, another had one in his chest. However, although seriously ill, all were still alive. Hunter knew that if men in that condition had been brought into his field hospital and operated on in the usual manner, they would all almost certainly have died. After this experience Hunter was extremely reluctant to operate at all on battlefield injuries unless they were immediately life-threatening, and often decided to let nature take its course with flesh wounds.

The Knife Man contains many more examples of Hunter’s pionering use of empirical evidence in medicine and, as such, is well worth reading by anyone interested in the scientific method. It also provides a fascinating insight into life in Georgian London. Notable characters appear in extremely unexpected ways in Hunter’s story:

  • James Boswell made frequent visits to Covent Garden  in order to the employ the services of local prostitutes, which was apparently quite normal for Georgian gentry, as was the consequence – a lifelong problem with gonorrhea, which Hunter tried to treat him for.
  • Hunter attended the birth of George Gordon (later Lord) Byron, who was born with a congenital deformity,  possibly a club foot. Hunter told his mother that it could probably be cured if he wore a specially constructed boot during infancy, but she didn’t take his advice.
  • Joseph Haydn was a frequent visitor to the Hunter residence during his time in London; he even wrote set some poems by Anne Hunter (John’s wife) to music. There were rumours of an affair, in fact. He also suffered from a nasal polyp, about which he sought Hunter’s advice. When the nature of the required surgery was explained to him, Haydn decided not to have it operated on.

I could give more examples, but that’s 1000 words, and it’s now sunny outside, so you’ll have to go and read the book, which I  recommend heartily. However, I really should point out that it’s not for the squeamish. The primitive surgical procedures deployed in the 18th Century are described in excrutiating detail and parts of the book make for very uncomfortable reading. If you don’t think you can cope with a detailed account of an operation, without anaesthetic,  to remove stone from a patient’s bladder, then perhaps this isn’t a book for you!

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