When we look at the sky by day we see the sun; by night we see the moon and stars. These, and all other objects which we see in the heavens, are called heavenly bodies. Astronomy is the science which treats of these bodies. The heavenly bodies are all of immense size, most of them larger than the earth. They look small because they are so far away. If we could fly from the earth as far as we please, it would look smaller and smaller as we went farther, until at a distance of many millions of miles it would appear as a little star. If we kept on yet farther, it would at last disappear from our sight altogether. If we lived on one of the heavenly bodies, it would be to us as the earth, and the earth would be seen as a heavenly body. In trying to think of the relation of the earth to the heavens, we may liken ourselves to microscopic insects living on an apple. To them the apple is a world, than which nothing bigger can be conceived. As this continent is to their apple, so is the universe of stars to our world. We may fancy how their ideas would have to be enlarged to make them comprehend the relations of the Atlantic and Pacific oceans; and then we may try to enlarge ours in the same way to understand the relations of the heavenly bodies.
About the Author: Simon Newcomb (March 12, 1835 - July 11, 1909) was a Canadian-American astronomer and mathematician. He made important contributions to timekeeping as well as writing on economics and statistics and authoring a science fiction novel. He studied mathematics and physics privately and supported himself with some school-teaching before becoming a functionary in charge of calculations at the Nautical Almanac Office in Cambridge, Massachusetts. In 1861, he took advantage of one of the ensuing vacancies to become professor of mathematics and astronomer at the United States Naval Observatory, Washington D.C. he set to work on the measurement of the position of the planets as an aid to navigation, becoming increasingly interested in theories of planetary motion. By the time he visited Paris, in 1870, he was already aware that the table of lunar positions calculated by Peter Andreas Hansen was in error. While in Paris, he realised that, in addition to the data from 1750 to 1838 that Hansen had used, there was further data stretching as far back as 1672 and was able to use the "new" data to revise Hansen's tables. He was offered the post of director of the Harvard College Observatory in 1875 but declined, having settled that his interests lay in mathematics rather than observation. In 1877 he became director of the Nautical Almanac Office where he embarked on a program of recalculation of all the major astronomical constants. Despite fulfilling a further demanding role as professor of mathematics and astronomy at Johns Hopkins University from 1884, he conceived with A. M. W. Downing a plan to resolve much international confusion on the subject. By the time he attended a standardisation conference in Paris, in May 1896, the international consensus was that all ephemerides should be based on Newcomb's calculations. In 1878, Newcomb had started planning for a new and precise measurement of the speed of light that was needed to account for exact values of many astronomical constants, when he received a letter from A. Michelson who was also planning such a measurement. Thus began a long collaboration and friendship. In 1880, Michelson assisted at Newcomb's initial measurement with instruments located at Fort Myer and the United States Naval Observatory, then situated on the Potomac River. Though Michelson published his first measurement in 1880, Newcomb's measurement was substantially different. In 1883, Michelson revised his measurement to a value closer to Newcomb's.