Your Astronomy Now

The Copernican revolution was one of the most important steps forward in the advancement of our knowledge of the universe.

The notion that the Earth is not the center of the universe, but actually is a planet, like Mercury, Venus, Mars, Jupiter, and Saturn, and therefore, moves through the heavens, was considered to be insane by most people. This theory contradicts what the bible says and what the church had taught since the days of the early church fathers. That the Earth is the center of the universe was considered to be so obvious that it would be insane to say it wasn’t so. Obviously, the sun, moon, planets, and stars revolve around the Earth. A corollary to the Copernican theory is that day and night are caused by the fact that the Earth spins. Well this can’t be so, people said. If the Earth was spinning around from west to east at the necessary speed, we would feel it. Not understanding inertia, people, even educated people made the argument that if the Earth was spinning and you jumped straight up, you would land somewhat west of the spot you jumped from.

Copernicus was certainly not the first to suggest that the Earth revolves around the sun. The idea had been discussed in ancient Greece, most notably by Aristarchus. There had even been a few European men who had suggested a sun-centered universe a century or so before Copernicus. What distinguishes Copernicus’s account is his detailed mathematical analyses of the consequences of the Earth’s motion around the sun. It was in large part, because his tables of the planets’ positions differed significantly from the tables produced by an Earth-centered system, thus enabling his theory to be checked in the long run, that his theory was eventually accepted. The errors that accumulated in his heliocentric (sun-centered) system were much smaller than the errors that accumulated in the geocentric (Earth-centered) system.

Of all of the great ideas in history, this notion, set forth by Nicholas Copernicus, in his book, De Revolutionibus Orbium Caelestium in 1543, was probably the most important, for its consequences were so far reaching. It set off a huge wave of controversy. At first it was just a ripple. But this ripple soon grew into a huge tidal wave of opposition to this heretical idea.

In order to appreciate why this idea was so vehemently opposed, one needs to understand the official cosmology of the church and its reasons for promoting this cosmology. This cosmology was largely derived from Dante’s Divine Comedy, which itself was, ironically, derived partly from Muslim teachings.

The fact that the Earth is a sphere is taken for granted in Dante’s work. It had been know since the time of Aristotle that the Earth is a sphere. (Actually it is a slightly distorted sphere, being fatter at the equator, but that discovery had to wait until Dominco Cassini) Circa 500BCE Aristotle set forth a clear and cogent argument for the spherical shape of the Earth. He pointed out that when ships disappear over the horizon, the main body of the boat disappears from view first, then the bottom of the mast, then the top. Also, people on ships see the bottoms of mountains disappear before the tops, as they sail away from the shore. This is a better argument than seeing the mast of a ship disappear after the bottom is no longer visible because it is hard to believe that the small ships of that time would be anything more than a dot on the horizon to a viewer on land. And why should there be a horizon at all if the Earth is flat?

Aristotle also pointed out that when one city views a solar or lunar eclipse as occurring , say, thirty degrees above the eastern horizon, another city, farther east, would report the same eclipse as occurring higher in the sky. Cities much further west would report no eclipse at all. He pointed out the absurdity of believing that there were two separate eclipses on the same day, each visible by one city and not the other. Even with an Earth-centered solar system, it was obvious that this could not be so. And he also pointed out, that travelers have long known that the North Star gets higher in the sky as one travels in a northerly direction. It was probably common knowledge before Aristotle that the Earth is a sphere. He was merely able to present the evidence more clearly and concisely than anyone else.

Dante paints a vivid picture of the universe, with the Earth at its center, hell being located in the very center of the Earth, and heaven, above. There are nine concentric spheres of hell, the innermost, being the most corrupt and horrible of them all, and the very center of the universe. Above the Earth’s surface, there are nice concentric spheres of heaven. Why nine? First there are seven concentric spheres, one for each naked eye planet and one each for the sun and moon. Beyond that, there is the sphere of the stars. A ninth sphere was added by the Muslims to account for the precession of the equinoxes.

The hero in Dante’s story descends progressively through all of the spheres of the Earth until he is in the very pits of hell. He comes out on the other side of the Earth, where purgatory is located, and then he ascends progressively through all of the heavenly spheres until he reaches the last one, the very throne of God.

This picture of the universe has man in an intermediary position, above the abode of the damned, yet within sight of heaven. This picture, with the demons below, the worst demon of all, Satan, in the very center, and the angels above, being progressively more angelic as one ascends through the heavenly spheres, places mankind in a precarious position, tempted by evil from below, inspired by divinity from above. This view of the universe was so congruent with Christian doctrine that it would not easily yield to a new view of the universe no matter how much evidence there may be in support of a new view. Ever since its publication, the cosmology of Dante’s book had been an important part of the theology of the Church, both Catholic and Protestant. With mankind’s position, balanced precariously between heaven and hell, it painted a vivid picture and reinforced the basic belief system of the church. Morality, cosmology, and theology were completely intertwined.

At first the opposition came only from Protestant circles. One of the first to speak out against this new heresy was Martin Luther. He called Copernicus a fool, pointing out, that the biblical story of Joshua clearly states that Joshua commanded the sun to stand still, not the Earth. Other Protestants soon joined in. Calvin cited the opening verse of psalm 93-”The Earth is stabilized that it cannot be moved.” Church officials began to search the bible with a fine tooth comb, looking for passages that “prove” Copernicus is wrong. Eventually the Catholic Church joined in the battle, banning Copernicus’s book in the year 1610.

Copernicus’s heliocentric theory was so violently opposed, not so much because it contradicted the bible, which it does, but because it made nonsense out of the official theology of Christianity. After all, the bible clearly describes the world as being flat, and its true shape had been known centuries before Hebrew scribes began to write the Jewish Bible, or Old Testament, as it is called by Christians. This should have been a cause for some caution in using the bible to “prove” that the Earth is the center of the universe. The church officials knew good and well that the bible was never meant to be taken literally, but were not averse to using literal interpretations when it proved useful their argument.

Here are the main objections to the heliocentric theory, as pointed out by the pope himself. If Earth is just another planet, circling the sun with the other planets, how can the Earth be a place of iniquity and sin, with devils below and angels above? He said that Copernicus’s theory makes a mockery of the ascension of Christ, because if the Earth is orbiting the sun, how could Christ have ascended up to heaven? If the stars are not the lights of heaven, but actually other suns, as the theory suggests, then God, in His infinite goodness, would have created inhabitants on them too. How could Christ have died for the sins of all of the inhabitants of these other planets? Many Copernicans believed that the universe was infinite. This was one of the worst heresies of all. If the universe is infinite, then where can the throne of God be located? No wonder the pope said that the Copernican heresy is the greatest threat there has ever been to Christianity and should be wiped out at all costs.

In 1610 Galileo went public with his own support of the heliocentric theory. He had observed that Venus goes through phases like the moon, and that these phases are in synch with its position relative to the sun. He also observed that Jupiter has four moons orbiting it, which contradicts an important argument of the Church. The opponents of the heliocentric theory said that the moon can’t be orbiting the Earth at the same time the Earth orbits the sun because God would not make things so complicated, and no one disagreed that the moon orbits the Earth. The phases of Venus had been correctly predicted by supporters of the heliocentric theory before Galileo had observed them. And the moons of Jupiter made it clear that objects can be orbiting another object, which itself is in orbit around the sun.

Galileo was put on trial and put under house arrest to effectively shut him up. The church considered him a big threat to their power because he was very vocal about the heliocentric theory and in fact had uncovered good evidence in its favor. Almost four centuries later, the Catholic Church officially apologized for the imprisonment of Galileo.

Eventually most Protestant sects were persuaded by the evidence. By the middle of the seventeenth century the accumulating evidence was too great to ignore. But the Catholic Church held its ban until 1822 on any books that espoused the heliocentric theory or treated the Earth’s motion as a reality.

One objection to the heliocentric theory had been the lack of any observed stellar parallax. If the Earth orbits the sun, then the stars should shift their positions as the Earth moves in its orbit. If accurate measurements of a star’s position are made six months apart, then a noticeable shift in the star’s position should be apparent. Despite many attempts to view stellar parallax, none was seen. This bolstered the Church’s argument against the heliocentric theory. For no parallax to be observed, the stars must be incredibly far away, and most people were not willing to believe that God would waste so much space by putting the stars so far apart.

Measuring stellar parallax became the holy grail of astronomy. Though there was enough evidence for the heliocentric theory by mid seventeenth century to convince all but the most die-hard fanatics, stellar parallax was not observed until 1838.

In principle, if a star’s position is carefully measured at six month intervals, then the diameter of the Earth’s orbit becomes a baseline from which simple trigonometry will give the distance to the star. It turns out that the stars are much farther away and farther apart from each other than almost anyone in the sixteenth or seventeenth century was willing to believe.

I believe that the true implications of heliocentricity have not been fully realized by most people, especially those who are prone to believing a literal interpretation of religious scripture. The number of stars in the known universe is beyond our ability to comprehend. The number of planets, of course, is unknown, but is almost certainly an incredibly huge number. The Earth is an insignificant speck in an unimaginably vast universe.