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The Ptolemaic system

Geocentrism is the belief that the sun, the planets and all the stars revolve around the Earth. You can thank the Old Testament for the lingering belief in this one. It has at least four verses claiming that the earth "cannot be moved," and one stating that the sun goes around the earth.


[edit] History

Ptolemy's universe with added cherubs.

Geocentrism was the standard model throughout the Western world during antiquity, the Middle Ages and the Renaissance.

Aristarchus of Samos was the first person to challenge the geocentric model, suggesting a heliocentric universe in the third century BCE but he had little following. Ptolemy's theory of the solar system placed all celestial bodies orbiting around the Earth, with epicycles introduced to compensate for the retrograde motion of planets such as Mars.

The ancient Greeks noted that if the Earth did move around the sun, the stars should appear to shift their positions from one part of the year to the next, a phenomenon they failed to observe. Alternatively the stars would have to be so ridiculously far away that the shift in position was too small to be seen by the naked eye, which would make for a ludicrously large empty space between the most distant planet, Saturn, and the "fixed stars". (Measurements dependent on naked-eye instruments could detect a parallax of something like one arc-minute, which would give a distance more than 300 times the distance to Saturn.)

Some late medieval scholars, notably Nicholas of Cusa and Nicolas Oresme, brought up the possibility that the Earth might move, but Copernicus revived heliocentrism in 1514, drawing on Aristarchus. [1] Galileo Galilei promoted the Copernican theory, provoking hostility from the Church who denounced it as heresy. Probably due to this controversy, Copernicus's book was still listed on the Index (the list of books banned by the Catholic Church) between 1616 and 1758.

[edit] Victory of heliocentrism

It was a mixture of different reasons that led to the final victory of heliocentrism (symbolized by the Catholic Church's capitulation in 1758). In 1551, the astronomer Erasmus Reinhold published the Prutenic Tables , astronomical tables, computed by the Copernican model, which were an improvement on tables based on Ptolemaic astronomy. In 1588, Tycho Brahe published his comprise system. Galileo's telescopic observations (announced beginning in his 1610 Starry Messenger) revealed a heavens different from the traditional conceptions: the phases of Venus, mountains on the Moon, satellites of Jupiter and spots on the Sun. Newton's 1687 Principia put the mechanics of the Solar System on a secure mathematical and physical basis. By 1729, it was an anticlimax when James Bradley discovered stellar aberration, measuring the orbital speed of the Earth in orbit.

[edit] For the Bible tells us so

Page from a Luther Bible which someone has helpfully scrawled on.

Geocentric is suggested in several Biblical passages, depending on how these passages are interpreted. In order of appearance, the verses are:

  • Joshua 10:12-13: On the day the LORD gave the Amorites over to Israel, Joshua said to the LORD in the presence of Israel: "O sun, stand still over Gibeon, O moon, over the Valley of Aijalon." So the sun stood still, and the moon stopped, till the nation avenged itself on its enemies, as it is written in the Book of Jashar. The sun stopped in the middle of the sky and delayed going down about a full day.
  • 1 Chronicles 16:30: Fear before him, all the earth: the world also shall be stable, that it be not moved.
  • Psalm 19:6: It [the sun] rises at one end of the heavens and makes its circuit to the other; nothing is hidden from its heat.
  • Psalm 93:1: The LORD reigneth, he is clothed with majesty; the LORD is clothed with strength, wherewith he hath girded himself: the world also is established, that it cannot be moved.
  • Psalm 96:10: Say among the heathen that the LORD reigneth: the world also shall be established that it shall not be moved: he shall judge the people righteously.
  • Psalm 104:5: (Bless the LORD . . .) Who laid the foundations of the earth, that it should not be removed for ever.
  • Ecclesiastes 1:5: The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose.

[edit] Modern geocentrism

In the modern world, small subsets of Biblical literalists and other scientifically illiterate cranks promote some form of geocentric worldview, although the details of their explanations vary.

Geocentric models claim the earth does not move at all, which means that the entire universe revolves around the earth daily. (This would mean that the stars and galaxies revolve around the Earth once every 24 hours, despite modern astronomy demonstrating that they are many light-years away and would therefore have to race round faster than light.[2]) A person can take a relativistic view, that "all motion is relative", and claim one cannot tell the difference between the earth being in motion and it being fixed. This has the drawback that the Bible does not make false statements about the fixity of the earth, but instead makes meaningless statements; and therefore it rarely comes up.

The Tychonian system. How could anyone living today mistake this for a sensible compromise?

Twenty-first century believers in a fixed earth may distance themselves from the Ptolemaic system of epicycles. Some call their model "geocentricity" in an attempt to make that clear. They may prefer a "compromise" position first suggested by Tycho Brahe: the sun revolves around the Earth, but the planets revolve around the sun. The Bible says nothing about the motions of the planets (and the stars), so any description of the movements of the heavenly bodies can fit the Bible, as long as the Earth is fixed and the sun is in a closed path around the Earth. Robert Sungenis, founder of Catholic Apologetics International, is an example of an influential modern geocentrist.

In addition to the minority of stubborn fundamentalists who insist on a geocentric model for dogmatic reasons, there are also a substantial number of undereducated people who hold a kind of passive geocentrism for ignorance, believing (if they even think about it at all) that the sun and stars must orbit the Earth daily because that it what we appear to see. According to recent polls in the United States, Great Britain and Germany, between 16% and 19% of people actually believe the sun goes round the earth.[3]

[edit] Debunking geocentrism

Modern geocentrists cite 19th century experiments which tried to measure the movement of the Earth, and got a zero answer. Such as the Michelson-Morley experiment[wp] and the use of a water-filled telescope by George Biddell Airy[wp]; two experiments meant to evidence aether, an hypothetical medium in which light would propagate. Alas both failed, as light seems to be content with no medium at all. Hopefully, the special theory of relativity perfectly account for these results in a heliocentric model.

[edit] Geocentrists' replies to arguments against their position

Geocentrists have some common replies to common arguments against their position:

  • They will argue that pictures from outer space showing the Earth in motion can be explained by the relative motion from the camera, not absolute motion of Earth.
  • They will argue that phenomena that reveal the motion of the Earth, such as the Foucault pendulum[wp] and the Coriolis effect[wp], are accounted for by appealing to something like Mach's principle[wp], by which any consequence of rotation of the Earth is the same as would occur with the movement of the "fixed stars" around a fixed Earth.
  • Phenomena such as the phases of Venus and Mercury and the apparent retrograde motion[wp] of Mars (and of the more distant planets) present no problem to modern geocentrism, for it typically adopts Tycho's model (in which those planets orbit the Sun).
  • Any geometric configuration of the Solar System, and thus any kinematic description of its motions, and any dynamic equations which have the Sun as the center, can equally (if not conveniently) be described with a coordinate system with the Earth as the zero point, for example in suitably chosen Lagrangian[wp] coordinates. (This is done within classical Newtonian mechanics.)
  • Objects as far away as Neptune (whose orbit has a radius of 4 light-hours) would have to move more than the speed of light to circle the Earth in 24 hours. In response, geocentrists will deny Einstein's theory of relativity[citation needed] or argue that the objects are moving at a normal speed through a space that is also moving. (In General Relativity, space itself can move faster than light.)
  • We read about how a major earthquake changes the rotation of the Earth, which proves that the Earth really has a rotation. The geocentrists point out, however, that that is only a calculated estimate, and that we not have the technology to measure the small differences that are involved. Even if this correlation with earthquakes should become measurable, as long as the cause of earthquakes are not well enough known to predict earthquakes, one cannot rule out that a change in the rotation of the heavens is the cause of earthquakes, or there is a common cause for both.

[edit] Daily rotation of the Earth

One important counterargument to geocentrism is that the rotation of the Earth isn't completely smooth: there is a slight deviation (the Chandler wobble[wp]). The planet's rotation speeds up and slows down slightly and the point of its axis changes a little.[4]

Heliocentrists can explain this easily: the Earth moves.

Geocentrists have to imagine that the stars and galaxies all wobble in (what appears to us) synchrony while Earth stays still. Since these stars and galaxies are millions of light years apart, however, their wobbles must all occur in the same pattern, but at different times according to their distance from Earth so that the light from these different objects reaches us at exactly the same time making it look simultaneous (for example, the apparent wobble of a star 100 light years away would actually be our observation of its wobble 100 years ago).

Such a universe model seriously strains credibility.

[edit] See also


[edit] External links

[edit] Footnotes

  1. Aristarchus of Samos
  2. Actually, the problem of faster-than-light travel occurs at the position of the planet Neptune.
  3. New Poll Gauges Americans' General Knowledge Levelsmodern medievalism: Geocentrism
  4. What is the Chandler wobble?
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