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- Herausgeber: Icon Books
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
- Veröffentlichungsjahr: 2020
John Gribbin, author of Six Impossible Things, shortlisted for the Royal Society Insight Investment Science Book Prize, presents a tour of seven fundamental scientific truths that underpin our very existence. These 'pillars of science' also defy common sense. For example, solid things are mostly empty space, so how do they hold together? There appears to be no special 'life force', so how do we distinguish living things from inanimate objects? And why does ice float on water, when most solids don't? You might think that question hardly needs asking, and yet if ice didn't float, life on Earth would never have happened. The answers to all of these questions were sensational in their day, and some still are. Throughout history, science has been able to think the unthinkable - and Gribbin brilliantly shows the surprising secrets on which our understanding of life is based.
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Praise for Six Impossible Things
‘[A]n accessible primer on all things quantum … rigorous and chatty.’
Sunday Times
‘Gribbin has inspired generations with his popular science writing, and this, his latest offering, is a compact and delightful summary of the main contenders for a true interpretation of quantum mechanics.… If you’ve never puzzled over what our most successful scientific theory means, or even if you have and want to know what the latest thinking is, this new book will bring you up to speed faster than a collapsing wave function.’
Jim Al-Khalili
‘Gribbin gives us a feast of precision and clarity, with a phenomenal amount of information for such a compact space. It’s a TARDIS of popular science books, and I loved it.… This could well be the best piece of writing this grand master of British popular science has ever produced, condensing as it does many years of pondering the nature of quantum physics into a compact form.’
Brian Clegg, popularscience.co.uk
‘Elegant and accessible … Highly recommended for students of the sciences and fans of science fiction, as well as for anyone who is curious to understand the strange world of quantum physics.’
Forbes
SEVEN PILLARS OF SCIENCE
The Incredible Lightness of Ice, and Other Scientific Surprises
JOHN GRIBBIN
CONTENTS
ABOUT THE AUTHOR
John Gribbin’s numerous bestselling books include In Search of Schrödinger’s Cat, The Universe: A Biography, 13.8: The Quest to Find the True Age of the Universe and the Theory of Everything, and Out of the Shadow of a Giant: How Newton Stood on the Shoulders of Hooke and Halley.
His most recent book is Six Impossible Things: The ‘Quanta of Solace’ and the Mysteries of the Subatomic World, which was shortlisted for the Royal Society Insight Investment Science Book Prize for 2019.
He is a Visiting Fellow at the University of Sussex, and was described as ‘one of the finest and most prolific writers of popular science around’ by the Spectator.
ACKNOWLEDGEMENTS
I am grateful to the Alfred C. Munger Foundation for financial support while writing this book, and to the University of Sussex for providing a base and research facilities.
As with all my books, Mary Gribbin ensured that I did not stray too far into the thickets of incomprehensibility. The remaining infelicities are all mine.
LIST OF ILLUSTRATIONS
The calculations of Anaxagoras (flat Earth) andEratosthenes (round Earth)
Giordano Bruno
Ernest Rutherford
Cecilia Payne-Gaposchkin
Marcellin Berthelot
Stanley Miller
Fred Hoyle
Raymond Gosling
Count Rumford
Hydrogen bonding of water molecules
Impact of Shoemaker-Levy 9 with Jupiter
xiiiWisdom hath builded her house, she hath hewn out her seven pillars.
Proverbs 9:1
PREFACE
Seven Pillars of Wisdom
J.B.S. Haldane famously described the four stages of acceptance for scientific ideas as:
i) this is worthless nonsense;
ii) this is an interesting, but perverse, point of view;
iii) this is true, but quite unimportant;
iv) I always said so.
The more I look at the history of science – and the longer I observe the ongoing development of science – the more I appreciate the truth of this aphorism. Looking back, it is easy to see how ideas that were once outrageous became accepted truths, and to feel a sense of superiority over those simpletons who, for example, thought that the Earth was flat. But even in my own lifetime I have seen ideas once regarded as wild speculations – including the Big Bang theory of the origin of the Universe and the non-locality of quantum entities – become received wisdom, pillars of science, while more ‘commonsensical’ alternatives – the Steady State theory, the idea that what happens in one location cannot instantly affect what happens xivsomewhere far away – have fallen by the wayside. How science works is as fascinating as the science itself, and to demonstrate this I have picked out seven examples which were each sensational in their day, and which have either become pillars of scientific wisdom or are well on their way to passing through Haldane’s four stages of acceptance. In order to restrict myself to seven, I needed some overall theme to link them, and I have chosen features of the Universe which are closely related to our own existence, and to the possibility of life elsewhere. This is, after all, the most important aspect of science as far as we humans are concerned.
Some of these examples are already pillars of science, others may be at an earlier stage – I leave you to judge which ones. But although all were sensational in their day, and some still are, a key feature of the development of science is a willingness to think the unthinkable, and then, crucially, to test those ideas and find out if they are good descriptions of what is going on in the real world. There are, though, some ideas which are impossible to categorise, and which, depending on your personal point of view, might be assigned to any one of Haldane’s stages. The biggest of these is a question that has puzzled philosophers for much longer than what we call science has existed, and with which I shall top and tail this book – are we alone in the Universe?
John Gribbin
November 2019
PROLOGUE
Worlds Beyond: Maybe We Are Not Alone
The Earth is round and moves through space. This was a dramatic realisation only a few hundred years ago. It flies in the face of common sense, so much so that some people still cannot accept it. You may not be one of those people, but do you just accept the story because it is what you were told as a child and ‘everybody knows’ it is true? Or have you ever stopped to think what a crazy idea this is, in terms of your everyday experience, and to consider the evidence?
To see how reasonable the idea of a flat Earth is, and how sensational was the realisation that it is round, we can look back to the Greek philosopher Anaxagoras of Athens, who was around in the fifth century BCE. Anaxagoras was no fool. He based his reasoning on the best evidence available to him, and given those facts his reasoning was correct. His conclusions turn out to have been wrong, but far more important than that is the fact that he tried to understand the Sun as a physical entity subject to the same laws as those that apply to things here on Earth. He did not treat it as a supernatural phenomenon beyond human comprehension.
2The trigger for Anaxagoras’ speculations was a meteorite which fell one day at Aegospotami. The meteorite was hot, so he inferred that it must have come from the Sun. It contained iron, so he inferred that the Sun must be made of iron – a hot ball of iron travelling across the sky. All this was completely logical in the light of the state of knowledge at the time. But it raised two intriguing questions that Anaxagoras set out to answer – how big must that ball of hot iron be, and how far above the surface of the Earth was it moving?
Anaxagoras wasn’t much of a traveller, but he had heard accounts from people who had been to the Nile delta, and beyond to the upper reaches of the Nile. These accounts mentioned that at the stroke of noon on the summer solstice (the ‘longest day’), the Sun was vertically overhead at a city called Syene, near the present-day location of the Aswan dam. You may have come across this tit-bit of information in another context; if so, be prepared for a surprise. Anaxagoras also knew that on the longest day at noon the Sun was at an angle of 7 degrees out of the vertical at the Nile delta. And he knew the distance from the delta to Syene. With this information, assuming the Earth was flat and using the geometry of right-angled triangles, it was a trivial matter for Anaxagoras to calculate that at noon on the summer solstice the Sun was roughly 4,000 miles (in modern units) above the heads of the inhabitants of Syene. Because the Sun covers roughly half a degree of arc on the sky (the same as the Moon, a dramatic coincidence outside the scope of this book), the geometry of triangles also told him 3that it must be about 35 miles across, roughly the same as the southern peninsula of Greece, the Peloponnesus.
The suggestion that the Sun was a natural phenomenon was so shocking to his fellow citizens that Anaxagoras was arrested for heresy, and banished for ever from his home city of Athens. It would be more than two thousand years, not until the seventeenth century, before another thinker, Galileo Galilei, also tried to explain the Sun as a natural phenomenon, and was also accused of heresy.
But only a couple of hundred years after Anaxagoras another Greek philosopher, Eratosthenes, used exactly the same data in a slightly different calculation. This is the version of the story you may have heard. Eratosthenes assumed that the Earth is spherical, and guessed that the Sun is so far away that rays of light from the Sun reach the Earth along parallel lines. With this assumption, the angle of 7 degrees out of the vertical measured at the Nile delta is the same as the angle subtended at the surface of the Earth by the distance from the delta to Syene, measured from the centre of the Earth (see diagram overleaf). This makes it possible to calculate the radius of the Earth. Because the angle is the same, the ‘answer’ is the same – 4,000 miles. But this is now interpreted as the radius of the Earth, not the distance of the Sun above the Earth. Because Eratosthenes was ‘right’, his is the version of the story recorded in textbooks and popular accounts, while Anaxagoras is ignored. But the moral is not who was right and who was wrong. Good theories are based on sound evidence and make predictions that can be tested. If the theory passes those tests, it continues to be used; if it fails those tests it is rejected. Taken together, the two theories (strictly speaking, hypotheses, but I won’t quibble) of the Greek philosophers combine to tell us that either the Earth is flat and the Sun is about 4,000 miles above it, or the Earth is a ball with a radius of about 4,000 miles and the Sun is at a vast but unknown distance. Later observations and measurements made it possible to decide which is a better description of the real world.4
Assuming the Earth is flat, it is simple to calculate the distance to the Sun
Assuming the Earth is round, the same observation tells us the radius of the planet
5There is also a cautionary aspect to the tale. Even a radical and far-sighted thinker who was not afraid to confront the authorities of his day in his quest for the truth could not rid himself of the preconception that the Earth is flat. Anaxagoras never considered alternatives. The history of science is filled with similar unfortunate examples of ideas that are built up with impeccable logic and complete accuracy, but are based on unquestioning faith in something which turns out to be completely untrue. Science should not be about faith, but about questioning cherished beliefs. Not that this always makes for a quiet life, as Giordano Bruno found to his cost. Mind you, Bruno seems to have gone out of his way to make his life difficult, and not just in the pursuit of science.
Historians (including myself) often date the beginning of modern science to the publication in 1543 of the book De Revolutionibus Orbium Coelestium (On the Revolution of the Celestial Spheres), by Nicolaus Copernicus. In truth, though, the book was not a sensation at the time; the ideas it contained did not gain widespread currency for the best part of a hundred years, and it did not go far enough in displacing ourselves from the centre of the Universe. Copernicus retained the idea that there is a fixed centre to the Universe, but moved this from the Earth to the Sun. He explained the apparent movement of the stars across the sky as due to the rotation of the Earth, but retained the idea that the stars and planets were fixed to solid spheres moving around the Sun. His most ‘heretical’ suggestion was that the Earth also is a planet, orbiting the Sun once a year, but that is as far as he went.6
Giordano Bruno Science Photo Library
7Bruno picked up Copernicus’ ball and ran off with it. Born near Naples in 1548, five years after the publication of De Revolutionibus, and christened Filippo, Bruno joined the Dominican order at the age of seventeen, taking the name Giordano, and became an ordained priest in 1572. He soon ran into difficulties because of his free thinking and taste for forbidden (or at least, controversial) books. He seems to have got into particular trouble for espousing Arianism, the belief that Jesus occupies a position intermediate between Man and God, making him divine but not the same as God. When things became too hot, he fled Naples, discarded his religious garments, and began a series of wanderings that took him to, among other places, Geneva, Lyon and Toulouse, where he took a doctorate in theology and lectured on philosophy. In 1581 he moved to Paris, where he enjoyed the safety of the protection of the king, Henry III, and published several works.
8In 1583 Bruno went to England with letters of recommendation from the French king, and moved in Elizabethan court circles where he met such notable people as Philip Sidney and (possibly) John Dee. Although he gave some lectures in Oxford on the Copernican model of the Universe, he was unable to obtain a position at the university, where his controversial views were derided by John Underhill, then Rector of Lincoln College and later Archbishop of Canterbury, who sneered at Bruno for espousing ‘the opinion of Copernicus that the earth did go round, and the heavens did stand still; whereas in truth it was his own head which rather did run round, and his brains did not stand still’.1 It appears, though, that it was as much Bruno’s personality as his teaching that made him unwelcome in Oxford. He seems to have been arrogant and unwilling to give much time to people he regarded as fools, and managed to put up the backs even of people who shared his views.
But this was less than half of what Bruno proposed. In 1584 he published two of a series of ‘dialogues’ in which he supported the Copernican cosmology, and by 1588 he was writing that the Universe is ‘infinite … endless and limitless’. So what were the stars? Pulling together the ideas expressed by Bruno in several places, he was the first person to realise that not only are the stars other suns, but that like the Sun itself they could each have their own family of planets. These other worlds, he said, ‘have no less virtue nor a nature different from that of our Earth’, and therefore they could ‘contain animals and inhabitants’.
9This would have been enough to bring him into further conflict with the Roman Catholic authorities, and Bruno is sometimes held up as a martyr for science. But his problems with the authorities ran so deep that these beliefs actually amount to no more than a footnote in the story of his later life and fate. In 1585, because of a deteriorating political situation between England and France, Bruno returned to Paris, then on to Germany and Prague, where he achieved the distinction (having already fallen foul of the Catholic authorities) of being excommunicated by the Lutherans. In 1591 he took a chance on returning to Italy, initially to Padua in the hope of getting a professorship. But the job went to Galileo and he moved on to Venice, the most liberal of the Italian city states. Not liberal enough, as it turned out. On 22 May 1592 Bruno was arrested and charged with blasphemy and heresy, his belief in the plurality of worlds just one of many examples in the citation. He might have got away with a relatively light sentence, but the Inquisition demanded that he should be transferred to Rome for them to deal with, and the Venetian authorities eventually bowed to pressure and handed him over in February 1593.
Bruno’s trial lasted for seven years, off and on, during which time he was imprisoned in Rome. Many of the papers relating to the trial have been lost, but the charges against him included not only broad-brush blasphemy and heresy but immoral conduct. Specific charges are thought to have included speaking and writing against the idea of the Trinity and the divinity of Christ, and doubting the virginity of Mary, 10mother of Jesus. He also made the shocking suggestion that different branches of the Christian Church should live in harmony and respect each other’s views. These were much greater sins in the eyes of the Inquisition than speculating about the plurality of worlds, but that went on the list anyway.* As usual with heretics, Bruno was eventually given an opportunity to recant, which he refused, and on 20 January 1600 Pope Clement VIII formally declared him a heretic. He is alleged to have made a threatening gesture at the judges when sentenced; he was burned at the stake on 17 February 1600, having first been gagged to prevent any heretical last words being heard by the onlookers. So here are some of his not-quite-last words which demonstrate the breadth of his thinking:
There is no absolute up or down, as Aristotle taught; no absolute position in space; but the position of a body is relative to that of other bodies. Everywhere there is incessant relative change in position throughout the universe, and the observer is always at the centre of things.
Although it quite quickly became appreciated that the stars are indeed other suns – Isaac Newton was one of several people 11
