For decades I have been fascinated by 19^th century celestial mechanics. This book is about one of my favorite stories from that field.

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

1. Part One: Newton to Neptune (1682–1846)

   • “The Immovable Order of the World”

     • Page 4
       

       This was the decisive climax in what we’ve come to call the Scientific Revolution , the long struggle through which mathematics supplanted Latin as the language of science .

   • “That Star Is Not on the Map”

     • Page 28
       

       Le Verrier would prove to be a man who catalogued slights , tallied enemies , and held his grudges close . But he never accepted a check as a measure of his true worth .

     • Page 43
       

       Le Verrier had confronted an uncomfortable fact , and then subjected it to theory , the theory , Newton’s system of the world , to risk a prediction that then proved true . If ever there was a demonstration of how science is supposed to advance , here it was .

   • Interlude: “So Very Occult”

     • Page 45
       

       “ I have not as yet been able to deduce from phenomena the reason for these properties of gravity and I do not feign hypotheses . ”

     • Page 49
       

       The heart of the Newtonian revolution lay with the claim that a purely mathematical argument was a sufficient account of events in the physical world — all of it , the full , unmeasured sweep of the heavens and our own mundane experience here on Earth : the same laws governing a ball dropping from a child’s hand or the tide sweeping away a sand castle to Neptune appearing first on the page and then in the eyepiece of Galle’s telescope .

     • Page 50
       

       It is for this reason that Newton is remembered not simply as a great thinker for his day , but as the greatest scientist ever . For all the secrets he kept , the private thoughts he harbored — for all the ( to our eyes , not his ) crazy , almost magical beliefs that informed his natural philosophy — the legacy of “ I feign no hypotheses ” remains . It is the cornerstone of the scientific account of material experience : rigorous observation and measurement of the physical world , expressed and analyzed in the language of number .

2. Part Two: Neptune to Vulcan (1846–1878)

   • Thirty-Eight Seconds

     • Pages 67-68
       

       A century and a half later, the one irreducibly extraordinary fact of this work remains how incredibly small an “error” Le Verrier uncovered. The unexplained residue of Mercury’s orbital dance came down to a perihelion that landed just .38 seconds of arc ahead of where it should every year. To put it into the form in which Le Verrier’s number became famous: every hundred years, during which Mercury travels a radial journey of 36,000 degrees, the perihelion of its orbit shifts about 1/10,000th beyond its appointed destination, an error of just 38 arcseconds per century.

       Tiny, yes. But the excess perihelion advance of Mercury retained one crucial property: it wasn’t zero. Le Verrier knew what such unreconciled motion must mean. If Mercury moved where no known mass existed to push it, then there was some “imperfection of our knowledge” waiting to be repaired.

   • A Disturbing Mass

     • Page 69
       

       Of all men, Le Verrier knew what came next: in his book-length report on Mercury, he said as much: “a planet, or if one prefers a group of smaller planets circling in the vicinity of Mercury’s orbit, would be capable of producing the anomalous perturbation felt by the latter planet….According to this hypothesis, the mass sought should exist inside the orbit of Mercury.’ ”

     • Pages 72-73
       

       Saturday, March 26, 1859….An object leaps into view: a small, regular dot, just inside the edge, or limb of our star. He [Edmond Modest Lescarbault] makes an estimate of its size: about one quarter the apparent diameter of Mercury. He has just missed its first appearance at the edge of the sun. Working backward from its apparent rate of motion, he estimates the time it crossed the solar limb at almost exactly four o’clock or, to be precise, at 3h 59m 46s P.M., plus or minus five seconds. He writes that down, using a piece of charcoal to scratch on a board. Another patient arrives and, likely with unrecorded frustration, he pulls his eye from his telescope. A few minutes later, he returns. The spot is still there, moving across the face of the sun. He tracks it continuously now, noting its nearest approach to the center of the solar circle, and then the instant and place it disappears over the solar limb. He records the time again: 5h 16m 55s. Total transit duration: one hour, seventeen minutes and nine seconds. If an asteroid were ever to be discovered within the innermost wards of the solar system, this is how it would reveal itself. Lescarbault meticulously transcribes his notes, and then… Does nothing… For nine months… Until, at last, he permits himself to write a letter to be delivered—by hand—to Paris.

   • “So Long Eluding the Hunters”

     • Page 103
       

       It feels unfair , as if one’s been granted a moment’s glimpse of an utterly different reality — that rectangle of Narnian forest through the open doors of a wardrobe , or a sudden vision of the train on Platform Nine and Three-Quarters.

     • Page 108
       

       Vulcan was to be found only when it was sought in the faith that it had to exist , never when anyone tried to confirm what had persuaded someone else .

3. Part Three: Vulcan to Einstein (1905–1915)

   • “The Happiest Thought”

     • Page 130
       

       …a significant step in building perhaps the single most powerful idea in twentieth – and twenty – first – century science : the recognition that the fundamental nature of reality in many of its facets is determined by the behavior of crowds that can only be understood in statistical terms , and not by direct links in a chain of cause and effect .

   • “Beside Himself with Joy”

     • Page 172
       

       On the 18th of November , 1915 , Einstein’s pen destroyed Vulcan — and reimagined the cosmos .

     • Page 173
       

       “ The years of searching in the dark for a truth that one feels but cannot express , the intense desire and the alternations of confidence and misgiving until one breaks through to clarity and understanding , ” he wrote , “ are known only to him who has experienced them . ”

   • Postscript: “The Longing to Behold…Preexisting Harmony”

     • Page 178
       

       It’s such a temptation to see the past as not just past , but as less clever than the present .

References

• In Search Of Planet Vulcan: The Ghost In Newton’s Clockwork Universe
• The Precession of the Perihelion of Mercury via Legendre Polynomials
• Perihelion Precession of Mercury
• Mercury’s Perihelion from Le Verrier to Einstein
• Various textbooks on General Relativity, e.g. Introducing Einstein’s Relativity: A Deeper Understanding, pp. 298-303