31 August 2010

Theology and the new physics: classical physics and the Newtonian world-view

5.2 The scientific revolution

The century and a half from the middle of the sixteenth century to the end of the seventeenth is, with some justification, regarded as a watershed in the development of the natural sciences. Beginning with the publication of Nicolaus Copernicus’ De revolutionibus (On the Revolutions of the Celestial Spheres) in 1543 and culminating in the appearance of Isaac Newton’s Principia mathematica (Mathematical Principles of Natural Philosophy) in 1687, a succession of radical thinkers revolutionised the disciplined study of the physical world. Among the main achievements of these early scientists were the establishment of a potentially simpler heliocentric model of the solar system in preference to the geocentric model favoured at the time (Copernicus, 1473–1543); the application of experimental method and mathematical analysis to the study of motion (Galileo, 1564–1642); the refinement and mathematisation of the heliocentric model (Kepler, 1571–1630); and the grand synthesis of these elements to show that all the situations under consideration, whether Earthbound or celestial, could be explained in terms of three mathematical laws of motion and a law of universal gravitation (Newton, 1642–1727).

Certain common assumptions regarding the nature of the physical world may be gleaned from this body of scientific work. Natural phenomena appear to be unimaginably complex but the founders or modern physics were committed to the view that underlying this complexity the world was rational and simple. In pursuit of this simplicity, they rejected the qualitative approach of traditional Aristotelian physics in favour of an emphasis on measurement. This reinforced a tendency (traceable back as far as the Ancient Greek philosopher Democritus) to distinguish between primary and secondary qualities. The former (mass, extension and duration) can be quantified and measured accurately, and were thought to be characteristic of an object in itself. They were, therefore, amenable to the combination of experimentation and mathematical analysis adopted by classical physics. Secondary qualities (such as colour, temperature and hardness), by contrast, could not be measured accurately and were, at that time, dismissed as subjective. The world envisaged by early modern science was well ordered, stable and predictable. Indeed subsequent generations of classical physicists were prepared to argue that, in principle, the future motion of every particle in the universe is predictable given an accurate knowledge of their positions, masses and velocities at some arbitrary point in time (see our discussion of Laplace in 1.17).

5.3 From method to world-view

This Newtonian paradigm had an impact that extended far beyond the methods of the virtuosi and the doors of the learned societies. According to Holton and Roller,
So impressive were the victories of Newtonian mechanics that, in the early part of the 18th Century, there spread a mechanistic world-view which asserted that man’s confident intellect could eventually reduce all phenomena and problems to the level of mechanical interpretations. The development of this new view through the extrapolation of the findings of science to philosophy was carried out mainly by philosophers, and it had important effects on economics, the ‘science of man’, religion, and political theory. (Holton and Roller, 1958:207)
However, in order to understand why something as far removed from practical concerns as a law of gravity should so catch the public imagination, we must recall that science does not exist in a vacuum. The peculiar attraction of Newtonian mechanics becomes much clearer when it is set in its wider cultural context (a task which is dealt with in detail by Toulmin, 1990:45–87).

Europe had been divided on religious lines after the Reformation. After an initial period of hostility, efforts at reconciliation (or, at least, at finding some way for divided communities to co-exist) began during the sixteenth century, which proved to be a brief golden age during which the arts, the sciences, and indeed a revived magical practice all flourished. However, efforts at reconciliation between Roman Catholic and Protestant failed. The first two decades of the seventeenth century were marked by growing intolerance, culminating with the opening shots of the Thirty Years’ War in 1618. In the wake of war came severe economic instability, famine and disease. Not surprisingly, apocalyptic speculation was rife, with Christ’s return widely expected to occur before the end of the century.

This anarchy inevitably generated a desire for order and stability. But where were these to be found? Religion had been tried in the fires of the Thirty Years’ War and found seriously wanting. The cultural and political leadership of Europe began to seek elsewhere for a secure basis for social order. A crucial part of their answer was the rationalistic philosophy of René Descartes (1596–1650). Perhaps human reason could succeed where religious tradition and authority had failed.

Rationalism offered the scientists of the seventeenth century a powerful device for underwriting the reliability and universality of their assertions. The mental discipline of subjecting their interpretations of nature to reason distinguished early modern science from competing ways of viewing the natural world. Classical physics, in turn, provided the exercise of reason (in conjunction with experimentation) with an early success story. The Newtonian paradigm in physics represented the successful adaptation of science to the new emphasis on universal truths of reason. And it did for the natural world what Cartesian rationalism promised to do for human society – it ushered in a new era of order and stability.

In the exhaustion that followed the Peace of Westphalia (1648), Descartes and Newton offered the intellectuals of Europe the hope of a new way forward. Within half a century their ideas dominated Western philosophy and science. The despair and hopelessness that led the intellectuals of 1650 to speculate about the imminent end of the world was swept away. In its place was a new vision – of a just society empowered by human reason, progressing towards an undefined goal in the future.

The success of the Newtonian paradigm in physics encouraged others to emulate it in other spheres. In particular, it offered the ruling élites a new and authoritative image for the ideal society. The modern nation state as it began to emerge in the eighteenth century was modelled upon the world of Newtonian astronomy. Like the solar system, it was centralised – a central authority (whether it be le Roi Soleil, a constitutional monarch, or a democratically elected government) wielding authority over successive circles of subjects, all of whom knew their places. On a smaller scale this centralised pattern was reflected in the paternalistic family. Social Newtonians (notably Newton’s staunch advocate Samuel Clarke) insisted that the order of nature indicated the rightness of the social order – that we should be content with our rulers and with our station in life. This is the outlook enshrined in that politically incorrect verse from ‘All things bright and beautiful’ by Cecil Alexander (1818–95):

The rich man in his castle,
The poor man at his gate,
God made them high and lowly
And ordered their estate.

According to Margaret Wertheim,
The Newtonian society, like the Newtonian cosmos, was a lawful, stable, immutable, and supposedly God-given order. Just as the planets remained fixed in their respective orbits, human beings were to remain fixed in their respective ‘stations’ . . . It was thus humanity’s moral duty to emulate in the social realm the order Newton had discovered in nature. And so, . . . Newtonian science in the eighteenth [century] was enlisted to justify the status quo. (Wertheim, 1995:132)

5.4 Change and continuity in the physical sciences

In the nineteenth century Newton’s laws of motion were successfully used to describe the motion of charged particles in electromagnetic fields, raising hopes that a complete description of the physical world could be achieved within the Newtonian paradigm. Indeed one of the most eminent physicists of the nineteenth century, Lord Kelvin, was so convinced of the completeness of Newtonian physics that in 1900 he told the British Association for the Advancement of Science, ‘There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.’ In the same year he told the Royal Institution that only two clouds remained to obscure the ‘beauty and clearness’ of Newtonian physics.

The first of those clouds was the failure of the Michelson–Morley Experiment to detect the motion of the Earth through the aether (the medium through which it was assumed light must be propagated). The other was the failure of classical physics to account for the colour of hot objects – the spectrum of black-body radiation. Kelvin may have dismissed them as clouds, but within a few years of his death they had grown into great storms. One gave rise ultimately to relativity theory; the other to quantum theory. Together these new theories amounted to a revolution in our understanding of the physical world.

However, while the content of the physical sciences may have changed radically, there remain underlying continuities. These continuities are highlighted by the marginal place of the new physics in elementary science education. Critics sometimes deplore the fact that very little of the new physics appears in the average school science syllabus. But such criticisms betray a superficial understanding of science. Content is less important than method and attitude. For today’s physics students, the role models are still men like Galileo, Kepler, Newton, Joule, Coulomb, Faraday, Maxwell and Kelvin. Einstein and Hawking may have become icons of science in the popular mind but they have so far had little impact on attitudes and methods. As for great women physicists, Marie Curie stands alone as a romantic figure in the popular mind – and her contribution to physics is still undervalued by a physics establishment that perpetuates the sexist myth that her husband Pierre was the creative member of the partnership.[1]

The formative assumptions of physics may be enumerated in a variety of ways. One example would be Coulson’s account of the scientific method in his Science and Christian Belief (1958:42–83). He presents an idealised vision of the scientist as one who comes to his task with honesty, integrity, hope, enthusiasm, humility, singleness of mind, willingness to co-operate with others, patience and critical judgment – the gifts of the scientific spirit. Furthermore he highlights certain assumptions without which science would make little headway and reminds us of their roots in the Judaeo-Christian world-view:
that common search for a common truth; that unexamined belief that facts are correlatable . . . that unprovable assumption that there is an ‘order and constancy in Nature,’ without which the patient effort of the scientist would be only so much incoherent babbling and his publication of it in a scientific journal for all to read pure hypocrisy; all of it is a legacy from religious conviction. (Coulson, 1958:75)
Specifically, it is a legacy of the mediaeval synthesis, the world-view that informed Christendom. That the legacy continued to influence physics in the twentieth century will be a theme of the next section.

[1] Wertheim (1995: 173) cites comments to this effect made at a meeting of the American Physical Society in 1972.

No comments: