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Physics in Antiquity

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Aristotle_Altemps_Inv8575Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. Also a mystery was the character of the universe, such as the form of the Earth and the behavior of celestial objects such as the Sun and the Moon. Several theories were proposed, most of them were wrong, but this is part of the nature of the scientific enterprise, and even modern theories of quantum mechanics and relativity are considered merely as “theories that haven’t broken yet”. Physical theories in antiquity were largely couched in philosophical terms, and rarely verified by systematic experimental testing.

Typically the behaviour and nature of the world were explained by invoking the actions of gods. Around 200 BC, many Greek philosophers began to propose that the world could be understood as the result of natural processes. Many also challenged traditional ideas presented in mythology, such as the origin of the human species (anticipating the ideas of Charles Darwin), although this falls into the history of biology, not physics.

Due to the absence of advanced experimental equipment such as telescopes and accurate time-keeping devices, experimental testing of many such ideas was impossible or impractical. There were exceptions and there are anachronisms: for example, the Greek thinker Archimedes derived many correct quantitative descriptions of mechanics and also hydrostatics when, so the story goes, he noticed that his own body displaced a volume of water while he was getting into a bath one day. Another remarkable example was that of Eratosthenes, who deduced that the Earth was a sphere, and accurately calculated its circumference using the shadows of vertical sticks to measure the angle between two widely separated points on the Earth’s surface. Greek mathematicians also proposed calculating the volume of objects like spheres and cones by dividing them into very thin disks and adding up the volume of each disk – anticipating the invention of integral calculus by almost two millennia.

Domenico-Fetti_Archimedes_1620Modern knowledge of these early ideas in physics, and the extent to which they were experimentally tested, is sketchy. Almost all direct record of these ideas was lost when the Library of Alexandria was destroyed, around 400 AD. Perhaps the most remarkable idea we know of from this era was the deduction by Aristarchus of Samos that the Earth was a planet that travelled around the Sun once a year, and rotated on its axis once a day (accounting for the seasons and the cycle of day and night), and that the stars were other, very distant suns which also had their own accompanying planets (and possibly, lifeforms upon those planets).

The discovery of the Antikythera mechanism points to a detailed understanding of movements of these astronomical objects, as well as a use of gear-trains that pre-dates any other known civilization’s use of gears.

Regrettably, this period of inquiry into the nature of the world was eventually stifled by a tendency to accept the ideas of eminent philosophers, rather than to question and test those ideas. New discoveries, such as Pythagoras’s deduction of the existence of irrational numbers, were suppressed, and technical knowledge was turned increasingly to the development of advanced weapons, rather than experimental investigations of nature. For one thousand years following the destruction of the Library of Alexandria, Ptolemy’s (not to be confused with the Egyptian Ptolemies) model of an Earth-centred universe with planets moving in perfect circular orbits was accepted as absolute truth.

Licensed under the GNU Free Documentation License. It uses materials from the Wikipedia.

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