## Space and the ancient philosophers

As far as we can judge, the ancient philosophers regarded the concept of space as self-evident. Their perception seems to have been the intuitive one of a domain within which there exist concrete things. The earth is 'a sphere poised in space'. The earth, which is a concrete thing, must exist somewhere. Space is where it 'lives'.

There could be other spaces, such as heaven — which, according to the Babylonians, is 'a hemispherical dome supported by the distant mountains'. It seemed reasonable to imply that the space of heaven is different from the space occupied by the earth. The early Greeks merged the two spaces, and pictured a round earth surrounded by concentric transparent spheres, each carrying a heavenly body. They seemed not to worry unduly as to what was in the space between the spheres.

Pythagoras (- 550 BC) was not comfortable with the concept of empty space, and believed that it was composed of a 'chain of integral finite numbers'. Of course, numbers whether integral, finite or not, are abstract entities, and in this sense Pythagoras' explanation was not particularly helpful or verifiable. He wanted to inject substance into space and, being a mathematician numbers were the most obvious things to use.

Aristotle (384-322 BC) believed that one can identify a 'place' in space. Every sensible body is by its nature somewhere'. He asserted that there is such a thing as 'absolute motion' from one place in space to another. Furthermore it follows that one can also define absolute rest as 'staying in the same place'. Aristotle's law of inertia can be stated as: 'A body, not acted upon by any force, remains at rest. '

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