The Rounding of the Earth
from the book, "Petrified Lightning"
The Rounding of the Earth
In the spectacular repair mission of the defective Hubble telescope, fascinating space walks were transmitted for the world to watch. The views were amazingly clear, and in the background are occasional glimpses of earth, very round and spherical looking, like the big blue marble described by astronauts.
Early viewers of the heavens could be excused for their myopic interpretation of the earth and sky. Their understanding was based on naked—eye observations and was limited by small—range wanderings on the home planet. Thinkers in most early civilizations accepted the earth as a flat, unmoving center of the universe, with sun, moon, stars, and planets circling around. Among most ancient peoples the view of the universe was embellished by religion: Egyptians regarded the earth as a flat square under a pyramid—shaped sky; Greeks placed their country in the center of a flat, circular earth with heavenly bodies circling around it; the early Hindu concept of the world was a plate resting on the backs of four massive elephants standing on a giant motionless turtle.
Many ancient scholars who observed and studied the heavens were able to delineate stars from planets, trace their motions and cycles, and draw some conclusions. No one knows who first imagined that the earth was round, but the idea didn't wait for Columbus. It may have been at the school of Pythagoras (580—500 b.c.) in a Greek colony in Italy that the theory of a round earth became a firm belief. This elite company of Greeks could easily observe how ships vanished over the horizon. Travelers related to them that as they sailed north new stars rose in the sky and those stars in the south dropped from sight. To members of the colony this was indisputable evidence that the earth was round. The Pythagoreans developed the idea of a round earth into a complete panorama of the universe, with the central earth surrounded by transparent spheres that carried the sun, moon, planets, and stars, all whirling in perfect harmony.
By the time of Aristotle (384—322 b.c.) many of the Greek thinkers were convinced that the earth was round. Aristotle himself pointed out that the round shadow of the earth on the moon during eclipses clearly showed the spherical shape of the earth. Even in the face of their advanced reasoning, Aristotle and his followers accepted the earth as the center of the universe, with the sun and all the planets revolving around it. Several questions remained unresolved. There was no explanation of why the planets moved slowly from west to east, while stars would have to fly at incredible speeds from east to west to make the trip once per day.
These mysteries were answered by the Greek astronomer Aristarchus of Samos (325—250 b.c.). He believed that the stars did not spin every day but that the earth did the spinning, and this caused the stars to appear to move across the sky at night. He also believed, correctly, that the earth traveled once a year in a huge orbit around the sun, as this would explain the change in star patterns throughout the year. He reasoned that the planets seem to move backward because they circle more slowly than the earth. Although this explanation was somewhat flawed, his reasoning that the planets (including earth) revolve at different speeds was accurate. And he placed the sun in its correct position at the center of the solar system.
Few people of the day agreed with Aristarchus. They labeled him a hoax, fraud, or lunatic, most likely because they resisted giving up the earth's position in the center of the universe. His fellow astronomers argued that if the earth orbited the sun, one would be able to observe parallax shifts in the stars.
Parallax shifts, which seem incredibly sophisticated for astronomers whose observations of the heavens were seriously limited, are easy to test. Holding a finger at arm's length in front of a contrasting background, one can see a motionless finger "jump" back and forth by looking at it first with one eye and then with the other. The finger appears to move to different parts of the background because of the distance, however small, between the two eyes.
Aristarchus argued that the stars were too far away from the earth for any parallax shift to be visible. Again he was correct, because slight parallax shifts are detectable only with modern telescopes.
With all their logic Aristarchus's theories fell on deaf ears, and the Greeks continued to place the earth at the center of the universe. His hypotheses were ignored by Ptolemy (a.d. 90—170), whose concepts of a geocentric (earth—centered) universe endured for 1,400 years. The traditional view of the solar system remained unchallenged until the Polish priest Nicolaus Copernicus (1473—1543) developed some radical notions about the order of heavenly bodies. Though he admitted that the idea was absurd, Copernicus began to think of a motion of the earth. As humbly as possible, so as not to offend the religious hierarchy of the day, he suggested that "the Sun, as if on a royal throne, rules the family of planets (including the godlike Earth) as they circle around him."
Copernicus's original manuscript credited Aristarchus with the shocking concept of a solar system 1,800 years before. Fearing the outrage of church leaders, he withheld publication of his book until he was over 70 years old and near death. His book, De Revolutionibus, was banned by the Church for over 300 years, but he did not live to suffer through the centuries—long battle.
Though the earth has been acknowledged as a spherical planet for many centuries, and views from space show its rounded outline unequivocally, we still have the Flat Earth Society.