Seventeenth Century Natural Science

From the Christianization of Europe in the early Middle Ages to the end of the Thirty Years’ War in 1648, the most important subjects for thought were religious. The great minds of Europe mostly spent their efforts on this field. With the discovery of America in 1492 came the first great break in the old order of things. The beginning of modern natural science was made by Copernicus, Galileo, Kepler, and Bacon, and from the middle of the seventeenth century, the growth of the natural sciences has been so rapid that they now constitute by far the greater part of that legacy from generation to generation which we call the world’s knowledge.

Before looking at the work itself of the scientists of the seventeenth century, it will give us a better bird’s-eye view of the development of the subject to run over the chief advances of the period.

The ideas of Galileo, Kepler and Bacon, whose work made memorable the first of the seventeenth century, have already been noted in a previous volume.

Harvey in 1619 rounded physiology by demonstrating the circulation of the blood. Soon afterwards (in. 1622) Asellius discovered the lacteal circulation, and in 1649 Olaus Rudbeck of Sweden found that these lacteals or lymphatics furnished the thoracic duct, and thus the heart, with the material for new blood. In 1690 Van Leeuwenhoeck strengthened Harvey’s theory by discovering the capillary circulation of the blood from the arteries to the veins.

In physics, the advances were many and great. Torricelli invented the barometer (1644) and Pascal (1656) by showing that the mercury rises to different heights at different altitudes above the earth, proved that it is the weight of the air which causes the rise of the mercury. Guericke in 1650 invented the air pump and in 1672 the first electrical machine. Newton proved the compound nature of light in 1666–71. Roemer in 1676 estimated its velocity by noting the difference in the apparent time of the eclipses of Jupiter’s moons, depending upon whether the earth is upon the side of its orbit nearest or farthest from Jupiter. The greatest variation observed was 16 minutes and 36 seconds, or 996 seconds, and the diameter of the earth’s orbit was thought to be about 190,000,000 miles. Light would then travel about 190,000 miles in a second. Huyghens took up the question of the nature of light and in 1678 developed his wave theory and his conception of ether as the medium through which light moves. In 1682 Newton worked out his law of gravitation and showed that weight is the result of an attractive force between masses of matter, that acts throughout all the immensity of the solar system.

A first foundation was laid in biology. Malphigi making use of the microscope discovered the capillaries between the ends of the arteries and the veins, the air-cells in the lungs, the color cells beneath the outer layer of the skin, and along with Grew in 1670 began modern botany by pointing out the cell-system in plants and that flowers differ in sex analogously with animals. In 1677 Leeuwenhoeck discovered the animalculae in water, thus opening up a vast world of microscopic life hitherto undreamed of, in 1690 the actual capillary circulation, and made many important investigations on insect-anatomy.

In chemistry, which began to break away from alchemy, Boyle discovered that gases are compressed practically in proportion to the pressure upon them (about 1665). Mayow in 1674 demonstrated that there is some component in the air necessary for breathing and combustion, but his discovery had to be remade a hundred years later.

Thus the seventeenth century saw the work of the world’s greatest astronomers, the foundation of physiology, the great law of gravitation, the first interpretation of sensation—light and sound in terms of motion, the first law in chemistry, and the first insight into the world revealed by the microscope.