Cosmic Inflation

David Kaiser

  • BuyTime Reborn: From the Crisis in Physics to the Future of the Universe by Lee Smolin
    Allen Lane, 319 pp, £20.00, April 2013, ISBN 978 1 84614 299 4

The Austrian polymath Ernst Mach exhorted his fellow physicists in the early 1880s to recognise that all was not well with their discipline. Two hundred years earlier, Isaac Newton had bequeathed to them a remarkable system of laws which made it possible for them to describe – and predict – the motion of everything from an apple falling from a tree near Woolsthorpe to the orbit of the Moon around the Earth. When Mach was still a child, it had been concluded on the strength of Newton’s laws that there must be an as yet unseen planet in the solar system, its presence deduced from subtle wobbles in the orbit of Uranus. In 1846, the discovery of Neptune was celebrated across Europe as one more victory for Newtonian physics.

But Mach wasn’t satisfied. Portraits show a brooding man peering through narrow spectacles and sporting the kind of beard that had become common among intellectuals of the late Habsburg era. He had done well-respected research in optics, and his studies of projectiles that move faster than the speed of sound – the resulting shock wave producing a characteristic ‘sonic boom’ – gave us the nomenclature of ‘Mach numbers’ (Mach 1, the speed of sound, was exceeded by test pilots in 1947; Mach 2, twice the speed of sound, in 1953). He also studied physiology and the psychology of perception. He could have had a professorship in surgery, but instead took chairs in mathematics and experimental physics. His final academic appointment was in the history and philosophy of science, a position he earned as a result of his persistent, withering critiques of Newton. He was as impressed as anyone with the practical applications of Newton’s laws. What troubled him was the array of assumptions that undergirded the enterprise. ‘The present volume is not a treatise on the application of the principles of mechanics,’ he wrote in the opening pages of The Science of Mechanics (1883). ‘Its aim is to clear up ideas, expose the real significance of the matter, and get rid of metaphysical obscurities.’ That last charge – ‘metaphysical obscurities’ – was meant to wound.

Mach was offended principally by Newton’s notions of absolute space and time. Over and over in The Science of Mechanics, he chides Newton for losing his way, cowering ‘under the influence of medieval philosophy’, growing ‘unfaithful to his resolve to investigate only actual facts’. For how could any reliable information ever be gleaned about such abstractions as ‘absolute space’? All we are in a position to investigate, he insisted, are relations between observable objects, such as the relative motion of real bodies. Yet Newton had built his entire system on an imagined platform of infinite, unbending, everlasting space and time, bolstered only by hand-waving about ‘the Sensorium of God’.

Mach countered that a proper science must be built on objects of ‘positive experience’: those which, at least in principle, could make some impact on an investigator’s senses. If some purported scientific object could not possibly affect the touch, taste, smell, hearing or sight of a diligent researcher, then better to cast it aside. Scientists shouldn’t allow such vacuous, metaphysical baggage to get in the way of progress. Accordingly, Mach refused to believe that atoms were real, despite the accumulation of indirect evidence, right up until he died in 1916.

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[*] I say ‘back’ because several strands of current thinking about the multiverse have remarkably rich histories, some of them traceable to Greek antiquity, as the philosopher Mary-Jane Rubenstein documents in Worlds without End: The Many Lives of the Multiverse (Columbia, 400 pp., £17.49, February, 978 0 231 15662 2).