THE PHYSICAL BASIS OF CHAPTER I EARTH AND MAN In the year 1610 Galileo, using his newly made telescope whose lenses were smaller than those in our spectacles, began his study of Jupiter and was finally able to prove the theory of Copernicus and to show that the earth revolved about the sun. Up to that time the earth had been considered the center of the universe with the sun and stars revolving about it. Centuries before man had begun to count the stars and give them names but he little appreciated the size of his task. In 1914 the Royal Observatory of Greenwich calculated that the stars now known aggregate some 1,600,000,000, of which 3,000 or 4,000 are visible to the naked eye. Our minds cannot grasp such numbers for they are greater than the total of minutes since the birth of Christ. These stars may be classified on the basis of the degree of heat. In the hottest, like two gaseous stars in the constellation of Argo, the spectrum shows lines belonging to no known element but bearing such relation to hydrogen that it is supposed to be a precursor thereof; hence these are called Protohydrogen stars. Helium is also present with hints of magnesium and calcium. In the helium-gas stars (Taurus, Algol) helium is prominent along with hydrogen, while carbon, oxygen and nitrogen can be detected. The Protometallic stars (Riegel, Sirius) show such metals as iron, copper and calcium. The Metallic stars (Aldebaran, Arcturus, Sun) show the common metals and the proto-lines disappear, while the coolest groups have fluted spectra or, in other words, are too cool to show the characteristic lines of their elements. This same gradation can be produced under high pressure by electricity, and thus a glimpse can be had in the laboratory of the process of world-making. Watery vapors appear and on the planets bodies of snow and water are found. It is our belief that the earth was once a molten mass whose surface has gradually cooled, and that this process left in the air and at the surface the materials of which organic beings are composed and thus prepared the basis for life. We must avoid the danger of assuming that this gradual cooling has been steady or uninterrupted. We know that North America went through several glacial periods when the temperature was much lower than that of today. We do not know what conditions are at the center of the earth, for our deepest borings have not carried us two miles below the surface. In 1661 Boyle suggested in his "Skeptical Chymist" that underlying matter in all its forms were minute units by whose aggregation the masses were formed. By the first of the nineteenth century this idea was developed into the atomic theory by the school teacher Dalton to whom we are also indebted for our system of naming chemical compounds. For countless ages simple substances like copper, silver, gold and iron had been known but that there were really only a small number of substances on earth was not realized. In 1774 Priestly and ▼ |