Space and time according to Isaac Newton

Is it meaningful to talk about empty space? Isaac Newton not only addressed the question of the fundamental nature of space, but also the nature of time, which up to then had been either ignored, or considered as a completely separate issue. His ideas are of historical rather than scientific interest, in that they do not give rise to verifiable predictions.

In his Principia Newton begins by stating 'I do not define time, space, place, and motion, these being well known to all', and then proceeds to contradict himself by offering definitions as follows:

Absolute time — 'of itself and by its own nature flows without relation to anything external'.

Absolute space — 'By its own nature and without relation to anything external remains always similar and immovable'.

* We will not discuss here our present view of continuous activity such as electromagnetic oscillations, or modern concepts of creation and annihilation of virtual particles in space which is devoid of physical matter.

In contrast to 'absolute space', Newton defined 'relative space as 'a movable dimension of absolute space, for instance space in a cavern which will at one time be part of absolute space, at another time another part of the same'. He defined a 'place' as 'that part of space taken up by a body which can be absolute or relative depending on what kind of space a body takes up'.

Newton's concept of the 'motion' of a body was 'the translation from one place to another, and could be absolute or relative depending on whether these places were absolute or relative'.

It is not surprising to find oneself confused by these definitions. Newton himself admits to being confused, by saying: 'It is however a matter of great difficulty to discover, and effectually to distinguish the true motions of a particular body from the apparent.

There seems little point in attempting to interpret Newton's definitions. Relative space is ill-defined and confusing, in that the use of the word 'relative' begs the question — 'Relative to what?'. It makes better sense to forget about Newton's absolute space and time, and to take Einstein's advice to 'wipe the slate clean', and follow a chain of reasoning in a series of logical steps.

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