The story of our world is a story that is still very imperfectly known. A couple of hundredyears ago men possessed the history of little more than the last three thousand years. Whathappened before that time was a matter of legend and speculation. Over a large part of thecivilized world it was believed and taught that the world had been created suddenly in4004 B.C., though authorities differed as to whether this had occurred in the spring orautumn of that year. This fantastically precise misconception was based upon a too literalinterpretation of the Hebrew Bible, and upon rather arbitrary theological assumptionsconnected therewith. Such ideas have long since been abandoned by religious teachers, andit is universally recognized that the universe in which we live has to all appearances existedfor an enormous period of time and possibly for endless time. Of course there may bedeception in these appearances, as a room may be made to seem endless by puttingmirrors facing each other at either end. But that the universe in which we live has existedonly for six or seven thousand years may be regarded as an altogether exploded idea.The earth, as everybody knows nowadays, is a spheroid, a sphere slightly compressed, orange fashion, with a diameter of nearly 8,000 miles. Its spherical shape has been knownat least to a limited number of intelligent people for nearly 2,500 years, but before thattime it was supposed to be flat, and various ideas which now seem fantastic wereentertained about its relations to the sky and the stars and planets. We know now that itrotates upon its axis (which is about 24 miles shorter than its equatorial diameter) everytwenty-four hours, and that this is the cause of the alternations of day and night, that itcircles about the sun in a slightly distorted and slowly variable oval path in a year. Itsdistance from the sun varies between ninety-one and a half millions at its nearest andninety-four and a half million miles