Scientists today tend to patronise the early Greek philosophers who, 2500 years ago, inaugurated enquiry into the nature of things. The Atomic Theory? A lucky guess, they allege. But Carlo Rovelli accords them, and especially Democritus, the key atomist, pride of place in his narrative: a see-saw battle between notions that the world consist of discrete units, beyond which we cannot go, and the idea of continuum without beginning or end.
Rovelli gives these abstractions a local habitation and a name, using the insights of the Greek philosophers and the Latin poet Lucretius, who wove the atomic theory into the passionate, sensuous and astonishingly prescient poem, "On the Nature of Things", and whose “we all spring from heavenly seed” finds an echo today in Joni Mitchell’s “We are stardust, we are golden...” The author belongs to the great Italian One-Culture tradition encompassing science and literary humanism that begins with Lucretius, and takes in Dante, Leonardo, Galileo, Primo Levi and Italo Calvino. Rovelli proclaims: “Our culture is foolish to keep science and poetry separated: they are two tools to open our eyes to the complexity and beauty of the world.”
A wonderful line of reasoning runs from the founders of Greek atomism to Einstein, who finally proved in 1905 that atoms are real, and even determined their size. Like the Greeks, Einstein is a touchstone throughout, although Rovelli misses one slight trick: in 1923, Einstein actually wrote a foreword for a new German translation of Lucretius's great poem, neatly capping the 2500-year story.
That atoms are discrete particles was the first answer to crystallise in the particulate vs continuum debate and Rovelli shows us how subtly right the Greeks were in their arguments. But in the 19th century, light, electricity and magnetism were all declared to be continuous wave phenomena. Then, in the early 20th century, matter and waves (or the force fields in which waves occur) were shown to have a dual nature, sometimes manifesting as one, sometimes as the other: hence the electron microscope, in which electrons, normally thought of as particles, behave like waves, enabling far smaller structures to be seen than with a light microscope. But now, 100 years later, the ultimate reality seems to be particulate: only in mathematics can something be infinitely smoothly connected: in Rovelli’s theory, even space itself seems, counterintuitively, to be composed of very tiny units beyond which you cannot go.
Rovelli’s quest, like that of thousands of physicists the world over, is to bring gravity within the scope of the otherwise all-embracing standard physical model that accounts for every force of attraction except for Newton’s equations of 1687. The latter would have sufficed to put a man in the moon or the Rosetta spacecraft on its asteroid even without Einstein’s later corrections; they work but we still don’t know why. It is a bizarre anomaly.
For most of the book, Rovelli’s exposition, guided by his Greek heroes, is enthralling in its clarity, vision and poetic wisdom. But the chase has a beast in view. The search for quantum gravity, the missing link in physical theory is Rovelli’s passionate research interest and when he comes up to the present, things get a little wild and woolly. Rovelli is so immersed in his theories that he loses some of his explanatory power: we have to take on trust his views on the loop quantum gravity that emerges from certain equations. Other physicists have a different set of equations pointing to string theory (which he does mention). At this point, the reader is likely to want to wait for some evidence.
Which is now just beginning to come in. Gravitational waves from a collision between two black holes were detected for the first time in February this year. These ripples in the fabric of spacetime can only show the wave nature of gravity, not its supposed granularity.
If the quest for quantum gravity in the latter half of the book is, as Rovelli admits at one point, tough going compared to the luminous poetic account up to the 20th century, that is because science works at the coalface of ignorance, hacking and hewing through rival conjectures until the best fit is achieved. He recovers his eloquent poise at the end, elevating scientific uncertainty to a great principle. In the teeth of all trammelling dogmas and creeds, he elevates Socrates’ modest admission to the status of a scientific credo: “I’m not sure”.
- Reality Is Not What It Seems by Carlo Rovelli, Allen Lane, £16.99
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