The Day Albert Einstein Destroyed a Planet

Thomas Levenson, The Hunt for Vulcan: ... And How Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe

Isaac Netwon, at the height of his fame, in his rooms at Cambridge

Imagine a renowned physicist predicted we’d find an entirely new planet, in our own solar system. The math holds, according to Newtonian physics. This particular scientist accurately anticipated a new planet once before, telling astronomers exactly where it’d be on a certain date. The prediction appears perfect, except… the planet isn’t there. That’s the situation faced by Urbain Jean Joseph Le Verrer, whose foretold intra-Mercury planet, Vulcan, never materialized.

November 2015 marks the centennial of Albert Einstein’s General Theory of Relativity. Marking the occasion, MIT science writer Thomas Levenson spotlights one of science history’s weirder, less-remembered occasions, the struggle to find planet Vulcan. Le Verrer, who used Newton’s mathematics to precisely locate the previously undiscovered planet Neptune, found an eccentric wobble in Mercury’s perihelion of orbit. The only conceivable explanation: an undiscovered planet or asteroid inside Mercury’s orbit.

Levenson’s narrative sweeps from 17th Century Britain, to Paris in the 19th, to Berlin in the 20th. He focuses on three major personalities in the development of physics: Isaac Newton, whose theories of gravity and motion described an orderly, predictable universe; Le Verrer, who turned Newton’s descriptions into tools to anticipate new discoveries; and Einstein, whose theories did the unthinkable, challenging Newton’s supremacy. This book reads like an epic novel.

Newton, who had fallen into reclusive midlife eccentricity, came very close to becoming a historical footnote. However, his friend Edmond Halley’s observations about comets rekindled Newton’s thinking about planetary orbits. Calculating equations from known observations, he realized seemingly unpredictable events actually had concrete explanations, attributable to a mysterious force he called “gravity.” Published in an era when alchemy still ruled, Newton’s principles threatened how Christian Europeans perceived the world.

French astronomer Pierre Simon Laplace proved Newton’s mathematics applied throughout the solar system. But, writing during the Napoleonic Wars, Laplace’s reasoning would go frustratingly untested during his lifetime. It fell to Le Verrer, a surprising unknown from a tobacco-making background, to test and perfect Newton’s theories. When he did the previously unthinkable, forecasting the location of an unknown planet without ever peeking into a telescope, Le Verrer became science’s most powerful personality.

A young Albert Einstein starting his career

Le Verrer’s theories came to dominate 19th Century astronomy. So when he confronted one of science’s most inscrutable puzzles, the slippage in Mercury’s apparent orbit, his explanation became dominant worldwide. Astronomers searched diligently for planet Vulcan, which absolutely had to be there. After all, the math resolved perfectly. Le Verrer predicted its location, mass, orbit… but, even decades after Le Verrer’s death, Vulcan resolutely refused to make itself visible.

Meanwhile, a Zurich patent clerk, Albert Einstein, began incrementally unpacking mysteries of physics, a process apparently propelled by daydreams and intuition. Theories like Special Relativity and the photoelectric effect transformed modern science. But only once he’d transitioned to the full-time professoriate did Einstein enjoy time enough to pursue his ultimate accomplishment, General Relativity. And, almost accidentally, Einstein happened upon an ironclad explanation why planet Vulcan couldn’t possibly exist.

Readers familiar with Thomas Kuhn’s theories about scientific advancement will recognize important themes in Levenson’s narrative. The importance of personalities, for instance: planet Vulcan’s staying power, despite complete absence of evidence, relied substantially on the fact that Le Verrer himself predicted it. Einstein, an unknown upon his first publications in 1905, faced pushback because he contradicted Newtonian physics. And dammit, no upstart ever challenges luminaries like Newton. Ever!

Or the importance of reasoning by analogy: Newtonian physics initially faced significant hurdles because it separated cause from effect. Planets move because motion persists, not because God propels creation. Einstein’s theories don’t behave like anything we’ll encounter in daily life, so straight-up descriptions fumble in most people’s understanding. Levenson makes Einstein somewhat comprehensible with analogies to moving trains, flying rockets, and workmen falling off roofs.

Through these themes, Levenson demonstrates not only how cool science is, but also how contingent. Our comprehension of reality may appear more complete than prior generations, but all explanations remain subject to tests. Einstein made errors and followed blind paths; just because we agree his theories are correct today doesn’t mean that outcome was inevitable. Science, Levenson demonstrates, is the product of people and culture as much as of reality.

For readers who, like me, love physics without truly understanding it, Levenson’s narrative serves two themes. It helps unpack the forces that shape modern scientific reasoning, often without our recognizing them; and it translates difficult scientific precepts into common language. Through his artful analogies and nuanced approach, Levenson’s science reaches the level of poetry. With gripping conflicts, fractious characters, and world-shattering discoveries, Levenson’s story outpunches even the best world-class novels.