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Does it favor a Heliocentric, or Geocentric Universe?


By Martin Allen - Posted on 27 July 2007

In a word neither. The purpose of the mechanism is clearly to position 'heavenly bodies' with respect to the 'celestial sphere', with reference to the observer's position on the surface of the earth. In order to achieve this, the mechanism has to use a geocentric model. However this does not imply that the manufacturer favoured a geocentric model of the universe. In fact it was Aristarchos of Samos (310 - c.230 BC) who first proposed a heliocentric solar system in 297 BC. Unfortunately proponents of the heliocentric universe were increasingly persecuted for their beliefs in Ancient Greece and in later times. It is highly probable that the maker of the mechanism was aware of the heliocentric universe, but it does not imply he favoured it.

The object of the mechanism is to make specific astronomical predictions. This requires a geocentric model, since actual observations require everything to turn around the observer, think of the coordinates you use to point your telescope. In fact, there is a slight discrepancy since the observer is not at the center of the Earth, which is the actual center of the geocentric model, but this was already taken into account in antiquity and was estimated by Archimedes in his paper "The Sand Reckoner."

The geocentric/heliocentric debate is more of a conceptual issue as geocentric will eventually be required for observations. Moreover, until the 17th century, astronomy was mathematical astronomy in which one constructs the best model fitting the data without giving physical reasons why the model occurs in nature. Since the geocentric and heliocentric models are mathematically equivalent, the distinction is once again moot.

Moreover, the heliocentric theory certainly didn't have any observational support at the time (experimental verification only came in 1838) and it loses conceptual significance without physical explanations such as gravitation and Newton's Laws. Therefore, there was no scientific reason to adopt a heliocentric model in antiquity. The only exception is Archimedes who did adopt it in his paper "The Sand Reckoner" because he wanted to use the largest theoretical model of the universe, which is the case for the heliocentric model in order to avoid parallax issues.

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