Robert P. Crease contrasts a physicist's account of awe with a historian's reality check.
Seven Brief Lessons on Physics
- Carlo Rovelli
Physics: A Short History from Quintessence to Quarks
- John L. Heilbron
These two concise tours of physics are delightful, each in their own way. In Seven Brief Lessons on Physics, physicist Carlo Rovelli appreciates the field's beauties in an expansion of articles he wrote for the Italian newspaper Sole 24 Ore. Science historian John Heilbron's Physics surveys the discipline from ancient times to today.
Rovelli begins by relaying his excitement at discovering the general theory of relativity for the first time, in the gnawed pages of a textbook he had used to plug mouse holes. Reading it on a beach in Italy, he was inspired by its disclosure of a simpler, deeper order to the Universe — the gravitational field is not diffused through space, but is space. It was “as if a friend was whispering into my ear an extraordinary hidden truth”.
He writes evocatively of the theory's many wonders: exploding universes, space collapsing into bottomless holes, time sagging and slowing and the unbounded extensions of interstellar space rippling and swaying “like the surface of the sea”. We are immersed not in an invisible rigid infrastructure, but in “a gigantic flexible snail-shell”. The metaphors are vivid, the visions dramatic. When this book was first published in November 2014 in Italy, it outsold E. L. James's blockbuster novel Fifty Shades of Grey (Vintage, 2011).
The flow of time is absent from descriptions of the world.
Through chapters on quantum principles, cosmology, particles, quantum gravity and thermodynamics, Rovelli maintains the awestruck tone of a practising physicist. Only in a final chapter on the place of humans “in this great fresco” does this stance lead him astray. It makes it hard to explain why some people struggle to comprehend science, and even distrust it. It tempts him into scientism — regarding the world that science describes as the real one. The flow of time, he suggests, is “absent from descriptions of the world”. Yet philosophical 'lived time' — the process of anticipating the future out of a past to allow the human experience of the present — is a fundamental condition of being human. It allows us, among other things, to create and marvel at scientific frescos. Placing himself as observer rather than participant, Rovelli forgets where he stands.
Heilbron's Physics is different in topic and tone. He uses the Greek word physica to name the ancient field, then traces how it morphed into physics. Physica seamlessly folded in astronomy, psychology and zoology; its idea of cause included form, purpose and the stuff of which things were made, as well as pushes and pulls. From this, Aristotle developed a 'theory of everything', which explained almost all phenomena experienced by humans, from the growth and behaviour of plants and animals to the patterns made by heavenly bodies. It included a deity that drew things into motion; and 'quintessence', a fifth element (in addition to the familiar earth, air, fire and water), which was needed to keep the theory consistent, explaining, for example, why heavenly bodies move in circles rather than in straight lines.
Physica did not become physics simply as a result of observant people adding pieces to a puzzle. It required transformations in the social ecosystem, such as who pays for knowledge and why; its social applications; and how it is communicated. Physica got a big boost from the Islamic world, where Aristotle's concept was highly regarded and translated into Arabic around the ninth century. But physics began to acquire its eventual outline in the West after the sixteenth century, with the generation of Francis Bacon, Galileo and René Descartes.
Fostered by the needs of centralized, bureaucratic states, the discovery of new worlds, the spread of universities and new industrial applications, the emergence of physics as we know it today was a process of “dedeifying and deanthropomorphizing nature”. Now, God is marginalized and 'dark energy', our new quintessence, is needed to make sense of it all. A theory of everything is an ever more remote goal.
Heilbron does not sneer at physica, but carefully examines it and the ecosystem in which it thrived. By the book's end, physics has split off into so many branches — radar, Earth science, space probes, accelerators, meteorology and so on — permeating so many spheres of human life that we begin to lose sight of the field as something coherent. And that is the point.
Whereas Rovelli's feel-good book ends with us gazing in wonder at the edge of “the ocean of the unknown”, Heilbron leaves us rooted in lived reality. “Physics has given civilization a somber, disturbing, and challenging world picture, many fertile and some terrifying inventions, and notice of responsibility for the outcome of the human story.” If it, too, outsells Fifty Shades, there is hope for humanity yet.
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Crease, R. Physics: Two shades of physics. Nature 526, 37–38 (2015). https://doi.org/10.1038/526037a
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