Does the Earth go around the Sun, or does the Sun go around the Earth?

That must surely be a very foolish question! After all, has not science proven that the Earth goes around the Sun? What fool would question that? The issue was settled hundreds of years ago!!

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Hardly a day goes by without people being reminded of the problem that Galileo caused during the Geo-Heliocentric controversy. There are books still being written by people whose goal seems to be to taunt Christians with respect to this controversy.

Many people think that this issue was proof that Galileo and other scientists found an error in the Bible. They do not hesitate to bring up the issue in almost every science-versus-faith discussion, to try and show that the Church was WRONG and Science was RIGHT. There is hardly a book that does not mention this controversy when dealing with science-faith issues. Even Christian authors have succumbed to the myth that Galileo somehow discovered the True motion of planets. We are admonished to submit to the pronouncements of scientists, because Galileo proved that science is the infallible way of acquiring True knowledge.

Before we cite quotations, we need some background information:

A BRIEF HISTORICAL BACKGROUND

Ptolemy Claudius of Alexandria (85-165 AD) He made precise measurements of celestial motions and wrote an influential book called the Almagest. His works were translated into Arabic and then Latin. He believed the Earth is a Sphere and Planets move in Epicycles, i.e. Cycles on Cycles. He based his work on the Greek philosopher Hipparchus, (fl. 147-126 B.C.) who rejected Heliocentrism as proposed by Aristarchus of Samos (fl. 270 B.C.)

Nicolaus Copernicus (1473-1543) His book called Of the rotation of celestial bodies was published posthumously. He was a Heliocentrist, and believed that Planets move in Circular orbits of uniform motion around the sun, even though he knew that the sun was off-center of the solar system. He discovered the heliocentric concept from the Greeks.

Tycho Brahe (1541-1601) Danish Astronomer. He tried to hold a middle ground between Copernicus & Ptolemy. He believed the Earth is immobile, other planets revolve around the sun and all revolve around the earth. He tried to convert Galileo from Copernicanism. He was an instrument maker, and accurate clocks were invented by his time.  He is the inventor of Sextant through which he made very accurate measurements of stellar positions.

Johannes  Kepler (1571-1630) A Heliocentrist. He continued the work of Brahe. He was greatly enamoured by astrology. He corresponded with Brahe & Galileo and proposed elliptical paths of planets around the sun, which obviated the need for epicycles. His calculations led to the notion that planetary motion could be represented geometrically as covering  equal areas in equal times.

Copernicus and Kepler both were of the opinion that the Solar System virtually exhausted the space of the universe.

Galileo Galilei (1564-1642)  Believed in circular planetary orbits. He published a book that brought the ideas to the attention of the Catholic church.

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Closely related to astronomy was the invention of accurate clocks.

All clocks must have two basic components:- 1- a regular, repetitive action to mark off equal periods of time., e.g. movement of sun across the sky with its background of stationary stars, candles marked in increments, oil lamps with marked reservoirs. 2- A means of keeping track of increments, e.g. the position of clock hands.

Here is a brief history of clocks:

1- First tools used to measure passage of time were the motion of celestial bodies. The motion of the sun is the measure of a Day. The motion of the Moon gives a close approximation of a Month. The position of the stars give a reasonably accurate measure of a Year.

2- Sundials in Egypt, about 1500 BC to 1400 AD

3- Weight driven clocks- 15th Century

4- Spring powered clocks- Peter Heinlein- 1500, Germany

5- First Pendulum clock, with error of less than 1 minute per day, Christian Huygens, 1656. First balance & wheel clock by Huygens in 1675.

6- Quartz clocks, precise to within seconds per day, 20th century.

7- Atomic clocks, precise to within one millionth second a year. One second is defined as 9,192,631,770 oscillations of the Cesium atom.

1840- Greenwich Mean Time; superseded by UTC- Coordinated Universal Time in 1972- Adjusted periodically because the earth’s rotation rate changes by a few thousandth of a second per day.

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ALL MOTION IS RELATIVE

WE CANNOT KNOW ABSOLUTELY WHICH CELESTIAL OBJECT IS MOVING AND WHICH ONE IS STANDING STILL.

WE CAN CHOOSE ANY SUN OR PLANET AS OUR REFERENCE POINT, AND THEN CALCULATE MOVEMENT OF OTHER BODIES IN RELATION TO THAT BODY.

Here is a collection of quotes by men who have understood the nature of motion.

The cosmologies of Copernicus [Heliocentrism] & Ptolemy [Geocentrism] are kinematically equivalent; both of them are descriptions of the same facts, and Ptolemy’s epicycles of the planets are the kinematic equivalents of the circular orbits of Copernicus.
Reichenbach, Hans- Philosophy of Space and Time- p210-211

Galileo and the Inquisition are only in error in the single affirmation in which they both agreed, namely that absolute position is a physical fact - the sun for Galileo and the earth for the Inquisition.

Alfred North Whitehead- An Enquiry Concerning the Principles of Natural Knowledge- 1919- p31.

The commonly held view is that Copernicus’s heliocentric model vanquished the competition, especially the geocentric view of Ptolemy, because it yielded better predictions of the positions of the celestial bodies. In actual fact, the predictions of the Copernican model were a little worse than those obtained via the complicated series of epicycles... the real selling point of the Copernican model was that it was much simpler than the competition yet still gave a reasonably good account of the observational evidence.

Casti, J.L. & DePauli, W.; Gödel- p166

Today we cannot say that the Copernican theory is ‘right’ and the Ptolemaic theory ‘wrong’ in any meaningful physical sense.

Fred Hoyle, Nicolaus Copernicus, Heinemann Educational Books Ltd., 1973, p78

The Copernican conception is indeed simpler, but this does not make it any “truer” since this simplicity is descriptive ... One description may be simplest for some phenomena while a different description may be simplest for others; but no simplest description is distinguished from other descriptions with regard to truth. The concept of truth does not apply here, since we are dealing with definitions.
Reichenbach, Hans- Philosophy of Space and Time- p219

And hence this affirmation: “the earth turns round” has no meaning, since it cannot be verified by experiment; ... such an experiment ... cannot even be conceived of without contradiction ...
Henri Poincaré- Science and Hypothesis- p117

... it is meaningless to talk of absolute motion.
Even the Copernican world-view appears to be shaken by this consideration. It makes no sense accordingly, to speak of a difference in truth between Copernicus and Ptolemy: both conceptions are equally permissible descriptions.
What has been considered as the greatest discovery of [western] wisdom, as opposed to that of antiquity, is questioned as to its truth-value ... the doctrine of relativity does not assert that Ptolemy’s view is correct, it rather contests the absolute meaning of either view.
Reichenbach, Hans- From Copernicus to Einstein, p 75,82

There is one more implication that modern science has perceived in the work of Copernicus. The same observational data that Ptolemy organized in his geocentric theory of deferent and epicycle can also be organized under the heliocentric theory of Copernicus. Despite the belief of the latter that the new theory was true, the modern view is that either theory will do and that there is no need to adopt the heliocentric hypothesis except to gain mathematical simplicity. Reality seems far less knowable than Copernicus believed, and today scientific theories are regarded as human inventions.

Morris Kline- Mathematics and the Search for Knowledge, p85

... the Ptolemaic theory of the solar system was abandoned in favor of the Copernican not because it failed to “agree” with all the facts, for it explained as much as the Copernican did, but because the latter, as Copernicus himself said, was “simpler,” more elegant mathematically, and a more harmonious addition to the body of science than the former.
... there was no intellectual inconvenience at one time in regarding the earth as the fixed center of the universe, nor was there any particular reason, socially or otherwise, why it should not have been accepted, nor was it inconsistent with the existent body of knowledge.
Randall, J. H.- Philosophy: An Introduction- p135, 139

Two thousand years ago the earth turned; then it remained immobile until recently, when it has again begun to turn. [!!!]
Nicholas Malebranche (1638-1715)- The Search After Truth- p371

All the known celestial movements can be explained on a geocentric theory, if it is sufficiently complex.
Lacey, A.R., Dictionary of Philosophy- p359

... in fact simplicity of the mathematical theory was the only argument Copernicus & Kepler could advance in favor of their heliocentric theory as opposed to the older Ptolemaic theory.
Is the path of the earth around the sun an ellipse? No. Only if the earth & sun are regarded as points and only if all other bodies in the universe are ignored. Do the four seasons on earth repeat themselves year after year? Hardly. Only in their grossest aspects, which are about all men can perceive anyway, do they repeat.
Morris Kline- Mathematics: The Loss of Certainty- p 344, 350

He [Copernicus] was able, in fact, to cite as a distinct advantage only the greater simplicity of his system. ... Here lies one of the reasons which led scientists to accept the Copernican system, even though it must be conceded that, from the modern standpoint, practically identical results could be obtained by means of a somewhat revised Ptolemaic system.
Hans Reichenbach- From Copernicus to Einstein- p18

WE CANNOT PROVE
IF THE EARTH IS MOVING
THROUGH SPACE OR
IF IT IS ROTATING ON ITS AXIS.

Absolute space, that is to say, THE MARK TO WHICH IT WOULD BE NECESSARY TO REFER THE EARTH TO KNOW WHETHER IT REALLY MOVES, HAS NO OBJECTIVE EXISTENCE ... THE TWO PROPOSITIONS:
“the earth turns around” and “it’s more convenient to suppose the earth turns around” have the same meaning; there is nothing more in the one than in the other.
Henri Poincaré, Science & Hypothesis; p116-117.

It may be convenient for certain purposes to regard the earth as the centre; but nothing can oblige us to do so. No part of the universe- Earth, Sun, or anything else- has any unique right to be called the ‘centre.’ Observed motions are all relative, and it is a matter of decision what point in the universe is to be selected as the central origin of reference.
So the view that the earth is moving is just as admissible as the view that it is at rest.
Toulmin, S. & Goodfield, J.-1961- The Fabric of the Heavens- p169

From the point of view of modern science... there is no absolute frame of reference, only frames which are more or less convenient to use for the purpose at hand. A geocentric frame is useful for everyday activities ... while a heliocentric frame is [useful] for solar-system mechanics ...
Wikipedia- Geocentric Model

Motion is change in position; it is clear, however, that it cannot be observed unless it is a change in position relative to a certain body and not relative to an ideal space point. Is it meaningful, under these circumstances, to speak of absolute motion or of motion relative to space, if motion relative to other bodies only can be observed?
According to this principle there exists only a motion of bodies relative to other bodies, and it is impossible to distinguish one of these bodies as being at rest, because rest means nothing but rest relative to another body, i.e.
rest is itself a relative concept.
Hans Reichenbach- Philosophy of Space and Time- p210

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That should be enough for any thoughtful person to understand that the church versus Galileo controversy took place because neither side understood the nature of motion and the nature of truth.

Does the Earth go around the Sun, or does the Sun go around the Earth?

Take your pick, whichever is most useful for the purpose at hand.

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