The Hunt for Vulcan

Science, philosophy and history are marvelously woven into Thomas Levenson’s new book, The Hunt for Vulcan … and how Albert Einstein Destroyed a Planet, Discovered Relativity, and Deciphered the Universe. The book opens with Newton’s Laws and the discovery of the planet Neptune. Riding on his success with Neptune, the upstart celestial mechanic Urbain-Jean-Joseph Le Verrier, predicted the existence of Vulcan, a body closer to the sun than Mercury that would explain part of the perihelion shift unaccounted for. Ultimately no evidence of Vulcan is found, nor is evidence needed once Einstein has had his say on the matter.

Levenson first lays the groundwork leading up to Newton’s Laws of motion. The story begins with Edmond Halley (of Halley’s comet fame) and the discovery of what seemed like an inverse square law in explaining the motion of planets around the sun. Halley seeks out Newton to help explain the behavior of orbiting objects grounded in mathematics. His nine-page response to Halley, “On the Motion of Bodies in an Orbit” turned out to be of great significance. Levenson writes that “Newton hadn’t just solved a single problem in planetary dynamics. Rather, Halley grasped, his friend had sketched something much greater, a newly rigorous science of motion of potentially universal scope.” Newton’s subsequent Principia was broad in scope covering, well, everything to do with how things moved. It certainly seemed to work with all known objects at the time at least when measured to some degree of imprecision.

With the discovery of Uranus via observation by William Herschel in 1781, the task of calculating its approximate orbit went to the brilliant mathematician Pierre-Simon Laplace. The problem is that when you add a new object to the system, it will affect and be affected by the motion of everything else. That the mathematics is highly complex and ugly is an understatement. Add to that, with more precise measurements in astronomy, differences between an idealized calculation and actual observations become magnified. But even after all that, Newton’s Laws and the power of mathematics continue to triumph, and bring into harmony what had seemed disparate in the motions of Jupiter and Saturn. If you could account for all the moving objects, you could perfectly know their future and past – at least as portrayed by Laplace in his great work, Celestial Mechanics.

The nineteenth century is where things get interesting. Better and more precise observations and the accumulation of more data begin to suggest potential problems. Mercury starts to misbehave, but Uranus is the big bad boy looking for a solution. Could Newton’s Laws be wrong? Levenson shines in bringing to light how the “scientific method” plays out historically, and laying out the philosophical conundrums surrounding what to do when there seems to be a conflict between theory and experiment. Here’s a different question: Maybe Newton’s Laws aren’t wrong but take on slightly different characteristics at different length scales? Uranus is so far out there – maybe there is an additional factor that does not make much of a difference at closer distances, but starts to be important farther out (or farther in – in the case of Mercury). Or maybe there are other superceding descriptions at different length scales, quantum mechanics for example (but that would take another century to figure out). Or maybe different forces have different strengths at different length scales – certainly classical electrostatics can be compared with gravitation.

But what if Newton’s Laws did not need any modification? What if there was some other orbiting body further out that was causing Uranus to “deviate” from its ideal calculated path given the presence of Jupiter, Saturn and the Sun. (The rocky planets closer to the sun have very little effect.) Le Verrier was not the first to make this suggestion, but he had the audacity and mathematical prowess to calculate how this other body might move based on the data from Uranus’ motion. The historical tale is full of twists and turns, and Levenson describes them engagingly (so if you’re interested, go read his book!). Let me just reveal that after Le Verrier had predicted where exactly to look in the night sky for this new object, none of the French astronomers did so. Nor did the English. A young German astronomer however did. And he saw a new planet! They named it Neptune (after lots of wrangling of course).

Newton’s Laws continue to reign supreme. What should we do about misbehaving Mercury? Maybe the same strategy will work. The now very famous Le Verrier does the calculations and makes a prediction of where to look. This "planet" even has an appropriate name – Vulcan. Why hadn’t anyone seen it before? Maybe because it is hidden in the sun’s glare and the only chance of catching it might be “during a total eclipse of the sun” according to Le Verrier. The story has its own twists and turns, but now both professional and amateur astronomers looking for a chance at fame and glory turn to the skies. Here’s the catch. Some of them “see” something “new”, but many others do not. Was their equipment not good enough? Did the weather conditions at different sites play a role? Is the object seen indeed new or is it an older known star?

When you are the limits of precision in measurement, imagination can start to play a role in interpretation. Given my interest in origin-of-life research, this reminds me of the controversies surrounding the Allan Hills meteorite controversy in 1996 and whether there were microfossils, and the more recent spat between Brasier and Schopf with regard to the Apex chert in the 2000s. In an interlude, Levenson provides contemporary examples in particle physics and Big Bang cosmology. He sets the stage by discussing the interplay between scientific theory and experiment/observation. (I’m quoting him below.)

“No shows are hardly alien to science. Theories predict. That’s their job. Ever since Newton and his co-conspirators consummated their revolutionary program of subjecting nature to mathematics, this has come to mean that particular solutions to systems of equations can be interpreted as physical phenomena. If a given mathematical representation hasn’t yet matched up with some phenomenon in the real world, that’s what’s called a prediction. From the theory of Uranus, Neptune; from the theory of Mercury, what, if not Vulcan?”

“Long gaps between prediction and observation always raise the question: what finally persuades science – scientists – to abandon a once successful idea? When do you take “no” for an answer?”

Indeed. When? We now know from many examples, that if scientists had followed a monolithic scientific “method”, we would not have made anywhere close to as much progress. (“Set the dials with the right question, pour data in to the funnel, and pluck knowledge from the other end. And, most important: when that outcome fails to match reality, then you go back to the beginning, work the dials into some new configuration, try again.”) Levenson’s book highlights the dilemma and the fuzziness in philosophy of science – it's one of the best parts of his book.

The tale closes with Albert Einstein, lone genius working in a patent office in Switzerland. Newton’s theory finally bends, literally, as does space-time, with the powerful tour de force that is General Relativity. The repercussions of the theory are bizarre, and science is indeed stranger than science-fiction. Two groups make observations during the 1919 eclipse. The group at Sobral confirms Newton’s Laws stand unmodified, while the group at Principe measures what Einstein predicts. We hear the triumphant story of Arthur Eddington’s confirmatory expedition, as if, the aha moment was figured out through the telescope. History turns out to be both more complicated and more interesting.

As I was preparing an overview talk of origin-of-life research this week, I was reminded of a lone German patent lawyer working quietly for years on an idea that would rival the mainstream view. Gunter Wachtershauser is not a household name since the conclusion to his theory is still an open question. As described by Robert Hazen, in his very readable and engaging Genesis: The Scientific Quest for Life’s Origins, “Wachtershauser, a chemist by training but a Munich patent attorney by day, erected a sweeping theory of organic evolution in which minerals – mostly iron and nickel sulfides, which abound at deep sea volcanic vents – provided catalytic energy-rich surfaces for the synthesis and assembly of life.”

I don’t expect this complex problem to be solved anytime soon (otherwise I would have switched fields). Wachtershauser’s out-of-the-box thinking has led to a new generation of scientists working to combine the best parts of multiple theories to understand the riddle of life. It has also highlighted the importance of interdisciplinary research. Biology, Chemistry, Geoscience, Physics (and a good dose of math) must come together and scientists must combine their expertise if they are to make headway. Will we find the smoking gun signal to life? Can we imagine what life’s solution might be? Will we see what we want to see? Will a fundamental scientific law be challenged? In a heady and exciting time, it’s important to remember the lessons of history.