Big Bang author dismisses ancient Greeks' contribution to modern science
Big Bang author and physicist Steven Weinberg's latest tome looks at the genesis of modern scientific theory
To Explain the World: The Discovery of Modern Science
by Steven Weinberg
The ancient Greek philosophers of Miletus looked for the underlying reality: Thales reportedly thought the world was made of water; Anaximander proposed a mysterious substance called the infinite; Anaximenes suggested air and Heraclitus, fire. Empedocles of Sicily nominated a mixture of water, earth, aether and sun as the fabric of all mortal things, and Democritus earned an enduring place in history with one fragment of observation: that all matter consisted of tiny particles called atoms. Sensations such as sweet and bitter existed only by convention. Reality consisted only of atoms and the void.
As they believed in an underlying reality that united all things, the ancient Greeks were like modern scientists, says Professor Steven Weinberg in his provocative new book, To Explain the World: The Discovery of Modern Science. But there the similarity ends.
None of them took it upon themselves to explain how their theories about reality accounted for the appearances of things. This wasn't just intellectual laziness, says Weinberg: "There was a strain of intellectual snobbery among the early Greeks that led them to regard an understanding of appearances as not worth having."
The later and greater Greeks - the ones who left long texts that did substantiate their theories - fare no better. "I confess that I find Aristotle frequently tedious, in a way that Plato is not, but although often wrong, Aristotle is not silly, in the way that Plato sometimes is," Weinberg writes in a chapter seemingly calculated to reduce philosophers and formal science historians to apoplexy.
He is less impatient with the Hellenic Greeks because they didn't seem concerned about religion and tackled questions that could yield answers.
So Eratosthenes of Cyrene in 240BC became the first person in recorded history to notice that the sun casts no shadow at noon at the summer solstice at Syene, on the Tropic of Cancer at what is now Aswan, while in Alexandria on the Nile delta at noon on the same day, it cast a small shadow. He measured the difference in degrees implied by the change in the angle of the sun's rays and found it to be 1/50th of a circle. From that, he concluded - and who among us today would have made the same leap? - that the distance between the two cities must be 1/50th of the circumference of the earth. (Wrong: the earth's circumference is 47.9 times greater than the distance between the two cities, but Eratosthenes had "done quite well".)
Aristarchus of Samos, who worked in Alexandria before Eratosthenes, however, "could have done better": he tried to calculate the relative sizes of the moon and the sun and their distances from the earth, with "impeccable" mathematics but faulty measurement. "The real difference between Aristarchus and today's astronomers and physicists is not that his observational data were in error," says Weinberg, "but that he never tried to judge the uncertainty in them, or even acknowledged that they might be imperfect."
This is an unabashed vision of then in terms of now, rather than as the world must have seemed then. It is also science history without the science; more precisely, a series of tentative and piecemeal questions about the cosmos that ends with the arrival of something that a modern physicist would recognise as science. In those terms, it is a history not of science, but of the questions from which modern science emerged.
Weinberg has done this sort of thing before. The book that made him famous even before his 1979 Nobel Prize in physics was an unequalled, utterly compelling history of creation called The First Three Minutes. This instant classic described the Big Bang from the first thousandth of a second of time to three minutes and 46 seconds afterwards, and then brought the chronicle of events to a close with the unforgettable line: "The universe will go on expanding and cooling, but not much of interest will occur for 700,000 years."
In this study, the approach is the same: Weinberg contemplates the initial conditions, pursues the trajectory of discovery, and ends the adventure where most of us think it begins: with Galileo and Newton. As in the first book, he appends an epilogue that sums up later thinking, and parcels up the detailed scientific reasoning in a series of appendices for those who want to know more.
There is a difference, however: when Weinberg wrote The First Three Minutes, the evidence that there really had been a Big Bang - a moment when time, space and matter came into being from nothing - was just a decade old. Everything he told us was new. This time he goes over territory examined and re-examined for the past 2,000 years; he writes with an 18th-century elegance that echoes Edward Gibbon. But he brings to it not a classical historian's perspective - rather, a modern scientist's.
This doesn't change the plot. Weinberg follows the familiar chain of reasoning from Aristotle to the great experimenters of the Abbasid caliphate centred in Baghdad and the later Islamic intellectual capital of Cordoba and ultimately to Copernicus, Tycho, Kepler and Galileo. He understands the intricate connection between religion and natural philosophy, but he doesn't endorse it: he is inclined to view some of the Hellenistic and Abbasid scientists as religious sceptics. (Persian scholar Omar Khayyam is still censored in Iran.) Bacon and Descartes both appear to be dismissed as "overrated".
At the end of the day, this book is concerned not just with how we arrived at what is now called science, but why it took so long. That is because Weinberg has a clear idea of the underlying reality. He is one of the architects - he even coined the term - of what is now called the Standard Model of matter, time and space: a theory that stands up to continuous testing by the Hubble telescope and the Large Hadron Collider. The short answer is that modern science is not what Plato, or Aristotle, or even Copernicus and Galileo, or anyone else was looking for. "It is impersonal. There is no hint in it of human concerns like love or justice. No one who studies the Standard Model will be helped to be a better person," he writes.
The impossible Platonic goal of a purely deductive natural science stood in the way of progress. The Greeks didn't test their theories by observation because they had never seen it done. Progress in science has been a matter of discovering what questions should be asked, and, he warns, nothing about modern science is obvious to someone who's never seen it done.
The world is a teaching machine, but all the lessons are unplanned and unpredictable. Newton marked a real discontinuity by formulating an approximation of reality that united all motion, and all matter, in the heavens and on earth, but even this marvellous achievement was an approximation. Einstein's theory of general relativity replaced it, but Weinberg says even that theory is doubtless an approximation to a more satisfactory one.
"Satisfactory", however, may not be the right word. It may never be possible to fully explain the world. The universe simply may not fit any framework humans can devise. Science offers joy, but not certainty. "Like me," Weinberg writes, "most physicists today are resigned to the fact that we will always have to wonder why our deepest theories are not something different."