4. The Age of Wonder, by Richard Holmes, pp. 76-113

Herschel on the Moon, 5-7

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In 1766 Herschel moved to Bath, where he was not only organist in the Octagon
Chapel but also played in the orchestra in the Pump Room. He got into an argument with the impresario of the orchestra, James Linley, over orchestral arrangements, and set up a rival orchestra for a season, but finally made up with Linley and combined forces with him. When Linley decided to move to London, Herschel became the sole director of the concerts. He also composed and gave music lessons.

In February 1766 he had begun his first Astronomical Observation Journal, while also reading books on astronomy and attending lectures by the astronomer James Ferguson in the Pump Room. He began collecting telescopes and studying their construction. He found that refractor telescopes -- the straight kind with lenses at each end of the tube -- were insufficient for observing the stars, and turned his attention toward the reflector telescope invented by Newton. The concave mirrors in reflector telescopes gather and concentrate more light and produce less distortion than refractors.

Before Herschel, astronomers treated the night sky as if it were "the interior surface of a decorated dome, inlaid with constellations.... But Herschel began to conceive of deep space. He began to imagine a telescope which might plunge deep down into the sky and explore it like a great unplumbed ocean of stars." But the kind of mirror he would need for a reflector telescope capable of the exploration Herschel envisioned was too expensive. So he decided he would make them himself, out of metal, not glass.

Herschel's brothers, Jacob, Dietrich, and Alexander, came to visit him in Bath, and in 1770 Alexander came to stay with William in a house he rented at 7 New King Street where he gave music and singing lessons. William was concerned about Caroline, who was now twenty-one, but her mother was reluctant to give up her free housemaid until he went to Hanover and promised to pay her for a maid to replace Caroline. She returned to England with him in August 1772. He began to give her lessons in English as well as singing and the harpsichord.

As in Hanover, Caroline found herself playing housekeeper, but with the addition of music lessons, English lessons, reading aloud from English novels, and talking about astronomy. "It took time for the full emotional rapport to renew itself between the tall, handsome thirty-four-year-old bachelor brother, driven and ambitious, and the shy, tiny, awkward twenty-two-year-old sister, who ... was bursting with unfulfilled dreams and longings."

For Caroline, William was initially the great  liberator who had taken her out of the German house of bondage. But later their roles would subtly change. As William would observe to Nevil Maskelyne, it was not always self-evident which was the planet and which was the moon. 

Herschel began work on the mirrors for his telescope, getting the tools he needed for grinding and polishing the metal from John Michel, a fellow astronomer in Bath who, like Herschel, had some unconventional ideas, "such as the existence of 'black holes' in space from which light itself could not escape."

The moulds for casting metal mirrors were formed from horse-dung, and after the molten metal was poured and cooled it had to be ground down into a concave shape. It then had to be polished continually for hours without stopping; otherwise the metal would harden and become useless. In addition, there was the danger that the furnace might explode. The house at 7 New King Street became "a pungent, chaotic workshop." Caroline would read aloud to William while he polished the mirrors: "Don Quixote, the Arabian Nights, Sterne's Tristram Shandy -- all tales of fantastic adventures or eccentric heroes." Sometimes she even had to feed him by hand while he worked as long as sixteen hours without a break.

A Victorian illustrator portrayed the collaboration of William and Caroline Herschel as "a comfortable domestic scene ... in an elegant drawing room.... In fact these epic polishing sessions took place [in] the unheated, stone-flagged basement [where they] were surrounded by tools and chemicals, and the distinct, pungent smell of the horse-dung moulds. It was dirty, monotonous and exhausting work."

Herschel's first five-foot reflector telescope, finished in 1774, had a six-inch diameter mirror and was mounted in "a beautiful octagonal case of gleaming mahogany." He used it to study the moon and the then-mysterious nebulae. "Even at this early stage Herschel has the notion of a changing universe, and that nebulae might hold some clue to this mystery." When he began studying nebulae, just under a hundred had been cataloged by the French astronomer Charles Messier. "Within a decade, by the mid-1780s, Herschel would have increased this tenfold, to over a thousand nebulae.... Herschel suspected that they were star clusters at immense distances, whose composition might hold a clue to an entirely new kind of universe."

Meanwhile, to assuage the uneasiness of Jacob and Anna about Caroline's living in England, he reported that she had a small millinery business that she was running successfully, as well as continuing her music lessons. She had begun to perform as a singer in his concerts at the Pump Room. In 1779, Jacob cut back on the number of music students he was teaching, and began to work on a project to compile a catalog of double stars. He had already discovered that the Pole Star, "the key to navigation, and the poet's traditional emblem of steadiness and singularity, for centuries," was in fact two stars. By facilitating the measurement of parallax, double stars, he thought, "might provide a method of gauging the earth's distance from the rest of the Milky Way."

Conventional ideas about the cosmos at the time was not only that it was only a few thousand years old, but that the universe was only a few million miles in extent. The "fixed stars" were thought to be in an unchanging pattern and their brightness to be "a function of their size, rather than their distance.... One of Herschel's most simple and radical ideas was to assume exactly the opposite." But people had begun to speculate that the universe was much larger and that there was a high probability of extraterrestrial life.

The interest in extraterrestrial life underlay Herschel's fascination with the moon, which he was studying when, in December 1779, William Watson Jr. came upon him looking through his telescope."This was Herschel's first really important scientific contact in England, one not made until he was forty-one. Watson was only thirty-three." They became friends quickly, and Caroline later recalled that Watson came home with Herschel that night and talked until the next morning. Watson arranged Herschel's election to the Bath Philosophical Society as "optical instrument maker and mathematician," and helped him with his mirror-making. He encouraged Herschel to submit thirty-one papers to the society. Some of them were so speculative that they would now be considered "thought experiments." Among the more outlandish of them featured Herschel's idea that the craters on the moon might be man-made and designed to provide solar power to the cities and towns contained within them.

In 1781, Caroline closed her millinery shop, but it took her some time to sell off the stock, so that she was away from the house at 19 New King Street when William made a momentous discovery. On March 13 he observed "a new and unidentified disc-like object moving through the constellation of Gemini. This discovery would change his entire career, and become one of the legends of Romantic science." In a footnote, Holmes makes this observation:

Romanticism introduced three important themes into science biography. First, the "Newton syndrome," the notion of "scientific genius," in which science is largely advanced by a small number of preternaturally gifted (and usually isolated) individuals. Second, the existence of the "Eureka moment," in which great discoveries are made without warning (or much preparation) in a sudden, blazing instant of revelation and synthesis. Third, the "Frankenstein nightmare," in which all scientific progress is really a disguised form of destruction.

But the sighting of the "disc-like object" was hardly a "Eureka moment." Herschel thought he had found a new comet, and the record in his observation book contains "no expression of excitement or anticipation." Gradually, however, he began to devote his attention to the object, first to prove that it was definitely in motion and therefore not a fixed star, and then to figure out whether it was really a comet, since comets typically had "a slightly blurred, fiery outline and a distinct tail or 'coma.'" This object had neither.

Even by April 6, he was still calling it a comet in his observation book, though "the sharp, round definition and the lack of any tail could only mean one thing: a new 'wanderer,' or planet. What in fact he had observed was the seventh planet in the solar system, beyond Jupiter and Saturn, and the first new planet to be discovered for over a thousand years (since Ptolemy)." When he finally decided it was a planet, he called it "Georgium Sidus" ("George's Star") after George III. It did not finally receive the name Uranus until the middle of the nineteenth century.

Herschel told William Watson about his "comet" on March 22, and Watson passed the word on to Nevil Maskelyne and Joseph Banks. Maskelyne still thought that Herschel was something of a crackpot, but he checked it out and reported to Watson that he thought it was a comet or a planet.

The Astronomer Royal was in a dilemma. He had no reason to accept Herschel as a reliable astronomer, and to declare a new planet prematurely might bring himself and the Royal Society into disrepute, and even ridicule. On the other hand, to reject what might be the greatest British astronomical find of the century, especially if the predatory French astronomers accepted it first (and even named it), would be even more damaging.... King George III was particularly fascinated by stars, and particularly keen to outdo the French.

Finally, Maskelyne wrote directly to Herschel on April 23, and called it a planet in his letter. Herschel responded with a paper called "An Account of a Comet" in which he outlined the process of his discovery, and made it clear that he, too, thought it must be a planet, though he didn't actually say so -- probably under Watson's advice.

In his report to Banks, Maskelyne referred to Herschel as "the musician of Bath" and as "lucky" for having "accidentally" discovered the planet. "This suggestion that the discovery had been 'accidental,' and that he had been 'lucky,' was to grow increasingly disturbing to Herschel," who knew that his patient and meticulous survey and careful measuring and recording had enabled him to identify the planet. Fortunately, the rivalry with the French played in Herschel's favor when Charles Messier wrote to congratulate him on his discovery and give "his opinion that this was very likely to be the seventh planet in the solar system.... As Maskelyne and Banks were only too aware, Messier's congratulations would soon carry the weight of the entire French Académie des Sciences." And astronomers in Germany, Italy , Sweden and Russia joined in confirming and praising Herschel's discovery.

In May, Watson took Herschel to London to meet his father and Maskelyne, and Banks "claimed it as a decisive British victory over French astronomy," and announced that Herschel was to be elected to the Royal Society and receive the Copley Gold Medal -- though it took another six months for the bureaucracy to process both honors. Banks also urged Herschel to name the planet "or our nimble neighbours, the French, will certainly save us the trouble of Baptizing it." It was then that Herschel proposed naming it after the king.

Herschel was, however, still irritated by the "continuing murmurs in some quarters of the Royal Society that his discovery had been in some sense 'accidental.'" He reiterated his contention that it was the result of "a regular review of the sky" in letters to European astronomers, and as late as 1809 he was insisting that it was no accident. But he also began to romanticize the discovery, claiming that it took place in a single night instead of being the result of "the critical nights of measuring between 21 March and 6 April 1781. The effect of this account was to present and engagingly romantic image of science at work; the solitary man of genius pursuing the mysterious moment of revelation."

The discovery sparked a new popular enthusiasm for astronomy, reflected by the bestseller of 1786, Introduction to Astronomy in Letters to His Pupil by John Bonnycastle, who pointed out the challenge that astronomers were making to the biblical chronology of the creation, and wrote:

"Astronomy has enlarged the sphere of our conceptions, and opened to us a a universe without bounds, where the human Imagination is lost. Surrounded by infinite space, and swallowed up in an immensity of being, man seems but as a drop of water in the ocean, mixed and confounded with the general mass. But from this situation, perplexing as it is, he endeavours to extricate himself; and by looking abroad into Nature, employs the powers she has bestowed upon him in investigating her works." 

Though the discovery of Uranus "became a symbol of the new, pioneering discoveries of Romantic science," and was even celebrated in verse by Erasmus Darwin in his poem The Botanic Garden, there were still skeptics about Herschel and his telescopes. So Herschel packed up his telescope and brought it to Greenwich, where Maskelyne was duly impressed by the quality and clarity of Herschel's mirrors and acknowledged that "they were far more powerful than any of the official observatory telescopes, and probably than any other telescope in Europe."

In May 1782 Herschel was presented to the king and appointed the King's Personal Astronomer at Windsor with a salary of £200 per year. William, Caroline and Alexander moved to Datchet, a village near Windsor, in July 1782. He brought his telescope to Windsor for a demonstration to the royal family. The teenage princesses, Charlotte, Augusta and Elizabeth, were particularly impressed by the astronomer, especially after, on a cloudy night, he rigged up cardboard models of Jupiter and Saturn, illuminated them with candles, and placed them on a distant wall, then focused down the seven-foot telescope so they could view them.

Stargazing became a pastime that especially impressed the young Coleridge, who never forgot that when he was eight, he was taken out into the fields by his father to look at the night sky. "His Romantic sensibility -- even at the age of eight -- already inhabited the infinite and the inexplicable." Keats remembered a time at school when "the boys whirled round the playground in a huge choreographed dance, trying to imitate the entire solar system, including all the known moons (to which Herschel had by then added considerably) ... a gloriously chaotic 'human orrery.'" Keats was awarded Bonnycastle's Introduction to Astronomy as a school prize in 1811. "Reading of Herschel, he enshrined the discovery of Uranus five years later in his great sonnet of 1816, 'On First Looking into Chapman's Homer.'"