Thursday, 9 July 2009

Greek Cosmology

Greek Cosmology
The earliest cosmology was an extrapolation of the Greek system of four elements in the Universe (earth,
water, fire, air) and that everything in the Universe is made up of some combination of these four primary
elements. In a seemlingly unrelated discovery, Euclid, a Greek mathematician, proofed that there are only
five solid shapes that can be made from simple polygons (the triangle, square and hexagon). Plato,
strongly influenced by this pure mathematical discovery, revised the four element theory with the
proposition that there were five elements to the Universe (earth, water, air, fire and quintessence) in
correspondence with the five regular solids.

Each of these five elements occupied a unique place in the heavens (earth elements were heavy and,
therefore, low; fire elements were light and located up high). Thus, Plato's system also became one of the
first cosmological models and looked something like the following diagram:

Like any good scientific model, this one offers explanations and various predictions. For example, hot air
rises to reach the sphere of Fire, so heated balloons go up. Note that this model also predicts some
incorrect things, such as all the planets revolve around the Earth, called the geocentric theory.
Middle Ages
The distinction between what mades up matter (the primary elements) and its form became a medieval
Christian preoccupation, with the sinfulness of the material world opposed to the holiness of the heavenly
realm. The medieval Christian cosmology placed the heavens in a realm of perfection, derived from
Plato's Theory of Forms

Before the scientific method was fully developed, many cosmological models were drawn from religious
or inspirational sources. One such was the following scheme taken from Dante's `The Divine Comedy'.

The political and intellectual authority of the medieval church declined with time, leading to the creative
anarchy of the Renaissance. This produced a scientific and philosophical revolution including the birth of
modern physics. Foremost to this new style of thinking was a strong connection between ideas and facts
(the scientific method).

Since cosmology involves observations of objects very far away (therefore, very faint) advancement in
our understanding of the cosmos has been very slow due to limits in our technology. This has changed
dramatically in the last few years with the construction of large telescopes and the launch of space-based

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