Moving with the planets
‘The heavens are telling the glory of God,’ Psalm 19:1.
There are certain basic beliefs that make science possible—beliefs such as the world is real, facts are real, experiments mean something, and that man can observe facts. These ideas are all derived from a belief that the world was created and man has dominion. Both historically and currently they underlie all scientific endeavour regardless of whether scientists acknowledge them or not. This is especially true of scientists who believe that life evolved by chance and seek to use the ‘creation’ based non-chance methods of science to prove it. Consequently, it is little wonder that science education is on the decline.
Despite the fixed creation beliefs which gave rise to science, human theories derived by applying these beliefs to the real world can change. History teaches us such theories have been repeatedly subject to change. An excellent illustration of this process is to trace the history of ideas on the movement of the planets with respect to the sun.
The ancient Greeks represent the earliest recorded reasoning concerning the movement of the heavenly bodies.
In about 300 BC Aristarchus propounded the idea that the sun was stationary in space with the Earth and planets rotating around it. Others thought that the Earth was stationary and the sun, moon and stars rotated around it. They reasoned that if the Earth was travelling around the sun there would be immense winds experienced on the Earth; and since these winds did not exist, therefore the Earth must be stationary.
We should explain here the origin of the word ‘planet’. It comes from Greek and Latin words meaning ‘wanderer’. It was originally applied to the sun and the moon as well as Mercury, Venus, Mars, Jupiter and Saturn. The reason being that while the stars appeared to be fixed in their relative positions, the planets moved relative to them.
A theory becomes established
Claudius Ptolemy, a Greek astronomer living in Alexandria about 150 AD set down the then current ideas on the geocentric (Earth as the centre) system. He said the planets moved around the Earth in circular orbits, because the Greek philosophers believed the circle to be an example of perfection.
Gradually, over the centuries, the Ptolemaic system had additions and alterations made to it. An extremely complex movement was superimposed upon the original circular orbits of the planets to account for their irregular motion. Ptolemy’ view became the academic view of the Middle Ages.
The church of the day (as it still often tragically does) simply accepted what the academics were saying. After that, it simply meant looking for Scripture to justify the Greek pagan belief that the Earth was stationary with the sun in motion around it. Ptolemy’s view became church theology and this set the stage for the clash with Copernicus.
The revolutionary Copernican system
Copernicus was a Polish astronomer who lived from 1473 to 1543. He proposed that the Earth moved around the sun because it resulted in a much simpler model. He just felt that he’d like to have things a little less complicated than the then-popular system indicated. His ideas have become known as the heliocentric system (the sun as the center).
The Italian astronomer Galileo joined with Copernicus in favouring the heliocentric system. The church would not have its paganized theology challenged and as a result was tried by the Inquisition for heresy in 1633.
The next step
The most significant scientific advance in the field of planetary motion was made by the German astronomer and mathematician, Johannes Kepler, who lived from 1571 to 1630. Beginning from the Copernican picture, he attempted to find the form of the planetary orbits. He tried to find out what form would fit the observed data. He dedicated twenty-five years of his life to performing laborious calculations on other people’ astronomical observations to try to establish the nature of the orbits.
He was disappointed at first when his calculations proved the orbits could not be circles but instead must be some sort of oval shape. Eventually he discovered that the data fitted elliptical orbits, and was overjoyed that the form was in fact an ellipse whose mathematical form:
x2/a2 + y2/b2 = 1
differs only slightly from that of a circle:
x2/r2 + y2/r2 = 1
Newton’ laws of mechanics
It was not until after Kepler’ death that the scientific community recognised the importance of his work relating to planetary orbits. Kepler’ findings formed the basis from which Isaac Newton later deduced his laws of mechanics by which the complex motions of the heavenly bodies could now be explained in terms of a single physical law (the law of gravitation).
Proof of the Earth’ motion
Today most people accept that the Earth is in orbit around the sun and rotating on its axis. The church, as in Galileo’ day, has made this almost doctrine. But it may be well to ask what proofs of this exist?
In view of the fact that circular orbits were first proposed by the Egyptians, Kepler triumphantly wrote, ‘I have stolen the golden vessels of the Egyptians to make out of them a holy tabernacle for my God, far away from the frontiers of Egypt’ (Ref 1, page 18). Some authors have suggested that Kepler lost his Christian faith when he discovered that the orbits were not circular, but this is definitely not substantiated from his writings. He was, in fact, a devoted Christian and Lutheran, who wrote such things as ‘God wants to be recognized from nature’ (Ref 1, page 31).
Tycho Brahe (1546-1601) was the first astronomer to suggest an experiment to determine whether the Earth was in orbit around the sun. He suggested measuring the angle to one of the closer stars (relative to other stars) at some point in time, then remeasuring it six months later when the Earth should be at a different point in space. If the Earth was indeed moving, the angle should change. The telescopes in those days were not accurate enough to detect the small change in angle involved; but with modern equipment the change in angle has been verified. For the closest known star the change in angle p is three quarters of a second of arc (60 seconds make 1 minute, 60 minutes make 1 degree).
There is one other indicator that the Earth is rotating in space. The fact that low pressure regions spin with a clockwise motion in the Southern hemisphere, yet in the Northern hemisphere the high pressure regions spin with a clockwise motion and vice versa raises the question as to what force is being exerted on these winds. Studies of rotating bodies show there is an apparent Coriolis acceleration, which acts sideways on moving objects. Only a Coriolis type acceleration seems to explain the Earth’s winds and this could only occur if the Earth rotates. The fact that the wind direction is always constant is evidence of the Earth’ consistent rotation.
Einstein’s final word
Currently, Albert Einstein has the last word on the subject of the form of planetary orbits. He calculated that if his theory of relativity was correct, an elliptical orbit would not be stable, but that the axis of the ellipse would be precessing around the sun (or shifting slightly). Calculations were done on Mercury, which being the fastest moving planet would be expected to show the greatest relativistic effects. Most astronomers now appear to accept that Mercury’s orbit does fit the prediction of Einstein’s theory. Most, but not all, and out of that minority may well come the next theory on the movement of the planets.
Scientific theories are changeable. Sometimes a theory is replaced by a more comprehensive theory, which makes little difference except in certain situations. At other times a theory has to be rejected altogether because it just does not agree with observations. The lesson to be learned is that it is a fools’ paradise to base any understanding of the Bible on the currently accepted theories of scientists whether it be in planetary motion astronomy or the evolution in biology. Scientific theories have come and gone. The Bible remains the same.
- Kepler: Life and Letters, Carola Baumgardt, Victor Gollancz Ltd., 1952.
- Introductory Astronomy, E.G. Ebblghausen, Charles E. Merrill Publishing Company, 19.