2 The clockwork Universe

2.1 Mechanics and determinism 1/4

2.1 Mechanics and determinism 2/4

» 2.1 Mechanics and determinism 3/4

2.1 Mechanics and determinism 4/4

2.2 Energy and conservation 1/2

2.2 Energy and conservation 2/2

3 The irreversible Universe

4 The intangible Universe

5 The uncertain Universe

6 Closing items

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Other titles in the Physical World series

Describing motion

Predicting motion

Classical physics of matter

Static fields and potentials

Dynamic fields and waves

Quantum physics: an introduction

Quantum physics of matter

Part 1 of 4 | Part 2 | Part 3 | Part 4

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Newton's good fortune was to be active in physics (or 'natural philosophy' as it would then have been called) at a time when the cause of Kepler's ellipses was still unexplained and the tools of geometry were ripe for exploitation. The physics of Aristotle was clearly inadequate, and all other attempts seemed unconvincing. The new astronomy called for a new physics which Newton had the ability and the opportunity to devise. He was the right man, in the right place, at the right time.

For years before Newton, people had been trying to understand the world from a scientific perspective, discovering laws that would help explain why things happen in the way that they do. Bits of knowledge were assembled, but there was no clear idea how these bits related to one another; understanding was fragmentary. Newton's great achievement was to provide a synthesis of scientific knowledge. He did not claim to have all the answers, but he discovered a convincing quantitative framework that seemed to underlie everything else. For the first time, scientists felt they understood the fundamentals, and it seemed that future advances would merely fill in the details of Newtonís grand vision. Before Newton, few could have imagined that such a world-view would be possible. Later generations looked back with envy at Newton's good fortune. As the great Italian-French scientist Joseph Lagrange remarked:

_{'There is only one Universe... It can happen to only one man in the world's history to be the interpreter of its laws.'}

At the core of Newton's world-view is the belief that all the motion we see around us can be explained in terms of a single set of laws. We cannot give the details of these laws now, but it is appropriate to mention three key points:

1. Newton concentrated not so much on motion, as on deviation from steady motion - deviation that occurs, for example, when an object speeds up, or slows down, or veers off in a new direction.

2. Wherever deviation from steady motion occurred, Newton looked for a cause. Slowing down, for example, might be caused by braking. He described such a cause as a force. We are all familiar with the idea of applying a force, whenever we use our muscles to push or pull anything.

3. Finally Newton produced a quantitative link between force and deviation from steady motion and, at least in the case of gravity, quantified the force by proposing his famous law of universal gravitation.
Continue on to Mechanics and determinism, part 4 of 4

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