Nicolas Copernicus: Founder of Modern AstronomyREV. MARTIN S. BRENNAN
Nicolas Copernicus (1473-1543), the founder of modern astronomy, was destined to become, through the publication of his heliocentric theory, one of the seminal figures in the history of scientific thought.
His observatory was the garret of a small farm house, and his instruments of observation were of the rudest workmanship. Copernicus, in his pursuit of astronomical knowledge, struggled under mountainous difficulties, as the telescope had not then been invented, and the law of gravitation and those of motion were entirely unknown. He devoted forty weary years of incessant labor to the establishment of his grand hypothesis. It was not until toward the close of his life and at the earnest entreaty of his friend, Cardinal Schomberg, that Copernicus published his great work De Revolutionibus Orbium Coelestium Libri VI. , which he dedicated to Pope Paul III.
Copernicus had a clear, mathematical mind, and acquired a great knowledge of astronomy. He was not satisfied with the ancient system of the world. To his mind it seemed complicated and unsatisfactory. It wanted symmetry and simplicity, whereas the well-known laws which the Creator had given to nature were extremely simple, though grand.
According to the old system the earth was globular and fixed in space, having neither a motion of rotation nor one of translation. The heavens were spherical and revolved completely around the earth once a day. Besides the diurnal motion of the whole heavens, the sun had a proper motion among the stars, and accomplished a complete circuit in a year. The planets were also said to have a movement among the stars, this being sometimes retrograde and sometimes direct; while at times they apparently lost all motion and seemed stationary. Hipparchus and Ptolemy taught that all heavenly motions were necessarily circular, and, to account for the loop-like paths of the planets, had to introduce a complicated system of eccentrics and epicycles. The planets were represented as moving in circles around fictitious centres, and these centres, again, around the earth.
The teachings of Copernicus may be reduced to two fundamental propositions. One is, that the earth makes a complete revolution on its axis every day, occasioning an apparent diurnal revolution of the heavens. The second is, that the sun, and not the earth, is the centre of motion; and that all the planets, of which the earth is the third in the order of distance, revolve around the central sun.
Copernicus illustrates his first proposition by pointing out various kinds of apparent motion. Sailors on a vessel in smooth water, losing consciousness of their own motion, imagine themselves at rest and the banks and trees moving. The stars are at an infinite distance, and to go around the earth in so short a space as twenty four hours would demand an infinite velocity. It is much more reasonable to believe that the small earth revolves than that the mighty heavens are impressed with this awful rapidity.
That the apparent annual motion of the sun among the stars could naturally flow from the real annual revolution of the earth around the sun, Copernicus' second proposition, may be easily shown to be the result of the laws of relative motion. As we are carried eastward by the earth's motion of translation, the sun appears to us to move westward with an equal velocity. Day after day the sun appears to go westward among the stars, because we are moving eastward, until in the lapse of a year, the earth having made a complete circuit of the heavens, the sun has apparently accomplished a complete circuit in the opposite direction.
The peculiar motions of the planets are also easily explained on the Copernican theory. In reality, the apparent motion of the fictitious centres already alluded to is due to the real motion of the planet around the sun, and the apparent motion of the planet in the small circle is owing to the real motion of translation of the earth. The earth and all the other planets move around the sun in the same direction, from west to east. When an outer planet and the earth are on the same side of the sun, they move along together in the same direction towards the east; but the earth moving more rapidly than the planet, gives the latter the appearance of moving backward or towards the west, or of retrograding. When the earth passes beyond the sun, it will then be travelling in the opposite direction to that of the planet, and so the planet will seem to move directly onward with a motion equal to the combined velocities of the earth and planet. If it is an inner planet on our side of the sun, it will move faster than we do, and so will glide along past us; but as it is thrown back on the heavens like to a star, and will appear to us to be on the side of the sun opposite to us, it will seem to go back on its path to meet us, or it apparently retrogrades. When beyond the sun, on the contrary, it will appear to us to have a direct onward motion in its path. In the parts of its orbit where a planet moves towards or recedes directly from us, it appears stationary.
The labors of Copernicus in astronomy were herculean. Primitive as were his means of observation, he arrived at a very accurate conception of the size of our solar system and the relative position of its members. Assuming the distance from the earth to the sun as unity, Copernicus computed the greatest distances of the other planets from the central orb as follows: Mercury, .405; Venus, .730; Mars, 1.666; Jupiter, 4.980; Saturn, 8.66. These distances as now estimated are: Mercury, .467; Venus, .728; Mars, 1.666; Jupiter, 4.952 ; and Saturn, 9.00. His figures, after all, are not so very wide of the mark.
Although Copernicus loved his favorite science with the ardor of a devotee, nevertheless he did not neglect the duties of his sacred office. It is said that he divided his day into three parts, devoting one to the calls of his ministry, another to the gratuitous medical care of the poor, and the third to scientific study. In the history of science there is no more beautiful character than Nicolas Copernicus.
Rev. Martin S. Brennan, A.M. "Nicolas Copernicus: Founder of Modern Astronomy." In What Catholics Have Done for Science. (New York: Benziger Brothers, 1887): 14-19.
Rev. Martin S. Brennan, A.M. was rector of the Church of St. Thomas Aquinas, St. Louis MO.
Copyright © 1887 Benziger Brothers
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