Adapted for the Internet from:

Why God Doesn't Exist
Mathematical Physics
only offers Ptolemaic
explanations

    Do you know what a Ptolemaic explanation is?

    2000 years ago Claudius Ptolemy wrote the Almagest, a book in which he summarized his lifelong
    researches in Astronomy. Ptolemy and some of his contemporaries attempted to explain how the Solar
    System works. They devised a complicated system of epicycles, deferents, and equants to account for
    the movement of celestial bodies around the Earth. Fig. 1 shows just how cumbersome and ridiculous
    Ptolemy’s final system as published in his Almagest indeed was.

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    Last modified 02/07/08


        Copyright © by Nila Gaede 2008
When it comes to science, Bill,
we follow in the footsteps of our
glorious ancestor Ptolemy. We
explain the motion of the planets
with warped space, that of the
galaxies with dark matter, and
that of stars and gases with
black holes.

Fig. 1   The music of the spheres

    The ultimate reason behind Ptolemy’s distorted and amusing explanations is that, despite contrary
    evidence coming from the lab, he refused to abandon his belief in the geocentric model. In fact, to account
    for weirder and weirder observations, the ancient astronomers were forced to devise ever more ludicrous
    explanations. One author explains:

    “ Unfortunately, the system still did not quite match observations. Sometimes the
       size of a planet's retrograde loop (most notably that of Mars) would be smaller, and
       sometimes larger. Ptolemy could not explain this even when he moved deferents
       off-center, for the change in loop size did not match with the change in speed. This
       prompted Ptolemy to come up with the idea of an equant. The equant was a point
       near the center of a planet's orbit which, if you were to stand there and watch, the
       center of the planet's epicycle would always appear to move at the same speed.
       Therefore, the planet actually moved at different speeds at different points in its orbit.
       By using an equant, Ptolemy claimed to keep motion which was uniform and circular,
       but many people didn't like it because they didn't think it was true to Plato's dictum of
       'uniform, circular motion.' The resultant system which eventually came to be widely
       accepted in the west was an unwieldy one, using two sets of epicycles, revolving on
       a deferent, offset by an equant which was different for each retrograde planet (then
       known to be only Mars, Jupiter, and Saturn), but it predicted the beginnings and ends
       of retrograde motion far more accurately than either earlier Platonic spheres or early
       (and falsely perfect) Copernican systems.”  [1]

    A Polish monk, Nicholas Copernicus, finally put an end to Ptolemy’s amusing system of epicycles and
    ‘retrograde’ explanations.

    Is it right for me to laugh at Ptolemy?

    Absolutely not!

    But here it goes anyway: "Ha, ha, ha." I don’t feel so guilty because, judging him by today’s standards,
    Ptolemy would have probably brought his authority to bear against a contemporary Copernican upstart.
    This habit of laughing at skeptics comes to us at least from the ancient Cynics. The mathematicians have
    been in the habit of manipulating peers against and sneering at isolated skeptics since the days of the
    Greeks. Plato, the first really big idiot of Mathematical Physics, was so damned cocky that he put a sign on
    his Academy door that read “Let none ignorant of geometry enter here.” Yet no one was as ignorant of
    Geometry as Plato!

    We should not lose sight of the moral of the story. The awkward, contorted, and forceful Ptolemaic
    explanation for the movement of heavenly bodies lasted for 1500 years until it was finally put to rest by
    Copernicus’s heliocentric system. Meanwhile, our ignorant forefathers believed in it wholeheartedly, so
    much so that the thugs of the Catholic Inquisition threatened to put Galileo on the rack if he didn’t recant.
    What died was the notion of epicycles and contorted explanations for how the planets move as they
    move. What didn’t die are the Ptolemaic explanations. What didn't die is the circus atmosphere. What
    didn't die is the peer review system so lethal to Science. The mathematical physicists picked these
    banners up from where they fell on the battlefield and carry them proudly to this day. The five key words
    of Mathematical Physics serve to show that Ptolemaism isn’t dead yet. One author asks:

    “ words such as mass, force, torque, work, power and energy. What do these words
       really mean”  [2]

    Yeah! What do these words really mean? I think that everybody would like to know once and for all.


A planet moves around a fixed point on an
embedded, rotating sphere. Here I show
only two such spheres with their respective
epicycles. Imagine swinging a ball at the
end of a string while you ride on a rotating
carousel. The center of the carousel is the
Earth. The ball revolving around your hand
is an epicycle. Ptolemy and others devised
this comical system to explain what they
observed when they looked at the night
sky. To explain more subtle phenomena,
they went further and developed deferents
and equants, concepts which essentially
mean that the Earth was slightly off center
within the spheres.