There have been many attempts to assign a precise date to the beginnings of the literary renaissance—as, for instance, 1453, the year in which Byzantium was captured by the Turks, and the treasures of its library scattered throughout Europe. But it is a futile task; the renaissance did not come overnight; but was a slow development of centuries.

It is the same with the renaissance of the scientific spirit, with which we shall be concerned in the present chapter. This revived only gradually after its thousand-year torpor. But if we had to select a single year, a good deal could be said for 1452, the year preceding that just mentioned. For in this year was born Leonardo da Vinci, whom many hail as having been the first scientist to disentangle his thought from all the confused and erroneous ideas of the Middle Ages, and to approach the study of nature in a truly modern spirit. With Leonardo, science adopts modern aims and modern methods. Thus it is not inappropriate to begin the present chapter with a brief mention of this truly extraordinary man.

leonardo da vinci (1452–1519). His birthplace lies near Empoli on the road from Florence to Pisa. The natural son of a Florentine lawyer, and of a common peasant girl who afterwards married a cowman, his fine appearance and engaging manner marked him out as one obviously suited to court life, and actually he was associated with the courts of Florence, Milan and Rome in turn.

We look on helpless while our material civilisation carries us at breakneck speed to an end which no man can foresee or even conjecture. And the speed for ever increases. The last hundred years have seen more change than a thousand years of the Roman Empire, more than a hundred thousand years of the stone age. This change has resulted in large part from the applications of physical science which, through the use of steam, electricity and petrol, and by way of the various industrial arts, now affects almost every moment of our existences. Its use in medicine and surgery may save our lives; its use in warfare may involve us in utter ruination. In its more abstract aspects, it has exerted a powerful influence on our philosophies, our religions, and our general outlook on life.

The present book aspires to tell the story of how physical science has grown, and to trace out the steps by which it has attained to its present power and importance. To do this fully we ought to go back to the dim ages when there was no physical science, to the times before our cave-dwelling ancestry had begun to wonder why the night followed the day, why fire consumed and why water ran downhill.

This we cannot do. The early history of our race is hidden in the mists of the past, and the facts we should most like to know about its early days elude our search.

We have now followed the fortunes of science as it came to Europe from the east, first impinging on Ionian Greece and then penetrating to Athens, to various outlying parts of the Greek mainland and to southern Italy. Finally, when its light was already beginning to fade in Greece, it turned eastward again and found a home in Alexandria, the magnificent city which Ptolemy I had built at the mouth of the Nile.

Here many subjects of study had seemed to work themselves out to their natural endings. Geometry, which had made such magnificent progress at first, came to a dead end; algebra had hardly yet arrived; physics, which had made a good start, had been strangled almost at birth; astronomy, after making the best of starts, had taken a wrong turning at the time of Aristarchus, and was now advancing along the wrong road.

Worst of all was the opposition of religion. We have seen how the Christians had burned a large part of the great library in 390; in 415 they had murdered Hypatia; and in 642 the Mohammedans conquered the city, closed down the university and completed the destruction of the library. Each attack drove a part of the school abroad, so that learning and learned men were scattered to many lands—to Greece, to Rome, to Byzantium, even to Persia and the east. We shall now see how these scattered threads were all drawn together in the great medieval empire founded by the Arabs.

This book was published posthumously in 1947. Sir James Jeans had seen and read the first proofs, but he died before the final touches could be added. Since publication a number of expert reviewers and readers have voluntarily supplied the publishers with notes of misprints in dates and names, and of places where the latest findings on matters dealt with had been overlooked. In the ordinary course Sir James Jeans would himself have revised his book in the light of these indications. As this was no longer possible the publishers have taken expert advice, and after collating the comments of several readers have put the preparation of the second edition into the hands of Mr P. J. Grant of the Cavendish Laboratory. They are grateful to all those who have helped in this way.

The three centuries we have just had under discussion formed a sort of intellectual ‘golden age’ in which science made more progress than in three millennia of Babylon and Egypt. But as this period approached its end, a change set in, and by the middle of the fourth century b.c., Greek culture had definitely begun to decline, and Greek science with it. A few years later, the decline was accelerated by the invasion and military conquest of the country by Alexander the Great. Yet events which seemed to be disastrous to science at the time may perhaps have been a piece of good fortune in disguise.

For Alexander now decided to celebrate his victories and consolidate his empire by building a new capital which was to be the most magnificent city in the world. He chose a site on the flat lands where the Nile ran into the sea, and called the still unborn city Alexandria, after himself.

He died in 323 b.c., his grandiose scheme still incomplete, and his kingdom was divided among all who could lay hands on a piece of it. Egypt fell to the lot of one of his generals, Ptolemy, who chose the still unfinished Alexandria as his capital and, more ambitious even than Alexander, aspired to make it the world's capital not only for government and commerce but for culture and intellect as well.