It particularly focuses on three characters who shifted scientific consensus from the Ptolemaic geocentric model of the solar system to a heliocentric one: Copernicus, Kepler, and Galileo. And characters is the right word, because Koestler digs into their personal quirks and foibles with gusto. If he is to be believed, these three key scientists were all temperamental to the point of self-destructiveness. In doing so, he was inspired by Ancient Greek writings, and in particular references to the heliocentric system that Heraclides of Pontos and Aristarchus of Samos proposed in the 3rd century BC. Copernicus was terrified by the prospect of criticism, so that it took decades for him to publish his conclusions On the revolutions of the celestial spheres only came out just before his death in
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It particularly focuses on three characters who shifted scientific consensus from the Ptolemaic geocentric model of the solar system to a heliocentric one: Copernicus, Kepler, and Galileo. And characters is the right word, because Koestler digs into their personal quirks and foibles with gusto. If he is to be believed, these three key scientists were all temperamental to the point of self-destructiveness.
In doing so, he was inspired by Ancient Greek writings, and in particular references to the heliocentric system that Heraclides of Pontos and Aristarchus of Samos proposed in the 3rd century BC. Copernicus was terrified by the prospect of criticism, so that it took decades for him to publish his conclusions On the revolutions of the celestial spheres only came out just before his death in But in fact, the publication itself was fairly irrelevant: it was tedious and actually more complicated than existing geocentric systems.
As previous astronomers had done, Copernicus explained complex-looking orbits using models in which planets rotated on circles which themselves rotated in circles known as epicycles. Epicycles were a very powerful modelling tool in fact, equivalent to Fourier series!
But the important thing was that heliocentrism, an idea which been floating around without much fanfare since the Greeks, was brought to greater prominence - inspiring others, particularly Kepler and Galileo. Kepler was prone to bursts of passion, alternating between fury and self-deprecation. He was also driven primarily by a philosophical taste verging on mysticism: his first system of astronomy matched the six known planets with the five perfect Platonic solids for aesthetic reasons, and was complete bunk.
So too was his theory that the positions of the planets were determined by the ratios of musical harmonies. Yet these instincts kept him pushing, mostly by accident, in the right direction.
His breakthrough came when given access to the meticulous observations of Tycho Brahe also quite a character: after his nose was chopped off in a duel, he wore a silver replacement. Why the delay? Firstly, Tycho was very well-funded, and took data collection unprecedentedly seriously note that this was all done before telescopes!
Secondly, Kepler deserves great credit for his persistence in testing his theories against that data, and throwing them out when they failed to meet it. Lastly, God was placed on the outermost sphere, furthest away from the Earth. Their combined influence had astronomers thinking in circles for almost years! More specifically, Koestler identifies five main obstacles to scientific progress between the Greeks and the scientific revolution.
The second was the geocentric dogma, the blind eye turned on the promising line of thought which had started with the Pythagoreans and stopped abruptly with Aristarchus of Samos. The third was the dogma of uniform motion in perfect circles. The fourth was the divorcement of science from mathematics.
The fifth was the inability to realise that while a body at rest tended to remain at rest, a body in motion tended to remain in motion. The main achievement of the first part of the scientific revolution was the removal of these five cardinal obstacles. These were all evidence that the Earth was less special than had been thought.
The book faced heavy criticism from other scientists, but eventually became accepted after Kepler threw his support behind it. This would have been unimportant, if not for his insistence that the Church start reinterpreting scripture based on the evident truth of Copernican heliocentrism, as shown by the existence of tides. A particularly damaging example: in his Dialogue concerning the two chief world systems, the views of Pope Urban are put into the mouth of a dimwit called Simplicio.
At this point, science was in a pivotal position. There was a growing acceptance that the two were fundamentally the same, but no agreement on what force drove celestial motion, or what planets would do without the influence of the sun, or even what weight meant in a celestial context. Why an equal area? Ideas were also floating around to do with reciprocal attraction between objects in a way that varied by distance, but nothing concrete - and the introduction of magnetism made people even more confused about which force might be doing what.
Consider his thought experiment of firing a cannonball horizontally from a mountain. If fired slowly, it will fall to the earth quite soon. If fired faster, it will curve around the earth a little before falling. Apart from this, there were almost no cases of two objects affecting each other except by some medium physically between them.
The one known exception, as mentioned, was magnetism - a helpful precedent for building acceptance of Newtonian gravity. Out of Copernicus, Kepler, and Galileo, the first and last never let go of the Platonic ideal of circular orbits. In addition to the mysticism mentioned above, one anecdote is particularly telling. Kepler believed that elliptical orbits had to result from the combination of two different forces: one linking a planet to the sun, and the other simply acting on the planet itself.
This is basically correct: the first is gravity, which pulls planets towards the sun; the second is centrifugal force or inertia, which prevents them from falling inwards. Overall I think reading this book is helpful in understanding what it looks like to be very smart and also very confused. This supports the Kuhnian view of scientific revolutions as driven to a significant extent by personal taste in paradigms.
The great discoveries which determined its course were sometimes the unexpected by-products of a chase after quite different hares. The same kind of thing seems to have happened in the evolution of thought at critical periods like the 6th century BC or the 17th AD. It is doubtful whether reasoned argument will play any significant part in the ultimate decision, but if it does, a clearer insight into the evolution of ideas which led to the present predicament may be of some value.
The muddle of inspiration and delusion, of visionary insight and dogmatic blindness, of millennial obsessions and disciplined double-think, which this narrative has tried to retrace, may serve as a cautionary tale against the hubris of science - or rather of the philosophical outlook based on it.
The dials on our laboratory panels are turning into another version of the shadows in the cave. My impression is that geocentric models with epicycles were generally considered part of the former category, because while they matched the data pretty well, there was no good explanation of why planets would move as if they were on wheels attached to wheels, when the existence of such wheels in the sky would be absurd.
The Church also had no problem with heliocentrism when presented as the former which Galileo refused to do. Note that the question of when we should treat theories as descriptive models or literal truth is still a key question in philosophy of science now under the headings of scientific anti-realism versus scientific realism.
See also this argument that even easily-avoidable censorship is dangerous.
Book review: The Sleepwalkers by Arthur Koestler
Life[ edit ] [Koestler] began his education in the twilight of the Austro-Hungarian Empire , at an experimental kindergarten in Budapest. His mother was briefly a patient of Sigmund Freud. In interwar Vienna he wound up as the personal secretary of Vladimir Jabotinsky , one of the early leaders of the Zionist movement. Fighting in the Spanish Civil War , he met W. Afraid of being caught by the Gestapo while fleeing France, he borrowed suicide pills from Walter Benjamin.
The Sleepwalkers : A History of Man's Changing Vision of the Universe