Читать книгу The Age of Wonder: How the Romantic Generation Discovered the Beauty and Terror of Science - Richard Holmes - Страница 26

Herschel later recalled the moment with appropriate gravity: ‘The moon being in front of my house, late in the evening I brought my seven-foot reflector into the street…Whilst I was looking into the telescope, a gentleman coming by the place where I was stationed, stopped to look at the instrument. When I took my eye off the telescope, he very politely asked if he might be permitted to look in…and expressed great satisfaction at the view. Next morning, the gentleman, who proved to be Dr Watson, junior (now Sir William), called at my house to thank me for my civility in showing him the moon.’¹⁰³

Caroline remembered it rather less formally. Herschel and Watson were so immediately taken with each other that very night that they burst into the house and began ‘a conversation which lasted until near morning; and from that time on [Dr] Watson never missed to be waiting on our house against the hours he knew my Brother to be disengaged’.¹⁰⁴

Watson warmly befriended Herschel, and encouraged his work even to the extent of helping with pounding horse-dung moulds and casting speculum mirrors. He quickly became what Caroline called ‘almost an intimate of the family’.¹⁰⁵ He had Herschel elected to the Bath Philosophical Society as ‘optical instrument maker and mathematician’ (no mention of musician), and over the next two years encouraged him to submit no fewer than thirty-one papers at its meetings. These included ‘On the Utility of Speculative Enquiries’, ‘On the Existence of Space’, and further unconventional observations on the moon. They are evidence of the extraordinary intellectual ferment that had seized upon Herschel.

His notion of the cosmos was already far from conventional, and several of these papers were what would now be called ‘thought experiments’. In his ‘Space’ paper, delivered on 12 May 1780, he astonished his audience with his radical thoughts on time and distance: ‘Huygens said that it was possible some of the fixt Stars might be so far off from us that their light tho’ it travelled ever since the Creation at the inconceivable rate of 12 million of miles per minute, was not yet arrived to us. The thought is noble and worthy of a Philosopher. But [should] we call this immense distance a mere imagination? Can it be an abstract Idea? Is there no such thing as space?’¹⁰⁶

In the case of his moon speculations, he raises the question whether a scientific idea has to be ‘correct’ to be significant. One of Herschel’s most ingenious ideas was that moon craters were artificially constructed circular cities (or ‘Circuses’), built especially to harness solar power for the lunar inhabitants: ‘There is a reason to be assigned for circular Buildings on the Moon, which is that as the Atmosphere there is much rarer than ours and of consequence not so capable of refracting and (by means of clouds shining therein) reflecting the light of the Sun, it is natural enough to suppose that a Circus will remedy this deficiency. For in that shape of Building one half will have the direct, and the other half the reflected, light of the Sun. Perhaps, then on the Moon every town is one very large Circus?’^{107 ♣}

So, besides the two main projects, to record all new double stars and all new nebulae, Herschel was also embarked on a third and partly secret programme in 1779: to discover life on the moon. For some time he did not risk sending this section of the lunar paper to Maskelyne at the Royal Society, but both Watson and Caroline were aware of it. This was one of the reasons he needed to construct better telescopes.

The moon project had begun with a long entry made in his Observation Journal for 28 May 1776. He saw ‘what I immediately took to be woods or large quantities of growing substances in the Moon’. With a certain angle of solar light, some of the lunar shadows looked like ‘black soil’ spread down a mountainside. Other puzzling stippled shadows, especially in the Mare Humorum, Herschel believed were enormous ‘forests’, made up of huge, spreading leafy canopies, or at least ‘large growing substances’. Because of low lunar gravity, this gigantic ‘vegetable Creation’ was evidently ‘of a much larger size on the Moon than it is here’.¹⁰⁸

Similarly, he tended to believe that there were so many of the smaller moon craters that they must be artificial constructions: ‘By reflecting a little on this subject I am almost convinced that those numberless small Circuses we see on the Moon are the works of Lunarians and may be called their Towns.’ Nonetheless, true science required not speculation but accurate observation and telescopic proof. ‘But this is no easy undertaking to make out, and will require the observation of many a careful Astronomer and the most capital Instruments that can be had. However this is what I will begin.’¹⁰⁹

The light-gathering power of Herschel’s seven-foot reflector allowed him to see many objects that no previous astronomers had accurately observed, or at least recorded. With Caroline taking notes at his dictation, they began to compose a new catalogue of double stars, and to develop a system of recording the exact time and position of any unusual stellar phenomena not previously catalogued by Flamsteed. By this means Herschel began to build up an extraordinary, instinctive familiarity with the patterning of the night sky, which gradually enabled him to ‘sight-read’ it as a musician reads a score. He would later himself use such musical analogies to explain the technique and art of observation.

In early 1781 it was decided to close down the millinery business at 5 Rivers Street. William and Caroline moved back to the substantial three-storey terraced house at 19 New King Street, where the telescope equipment was immediately set up in the fine little back garden: ‘beyond its walls all [was] open as far as the river Avon’. Here, as Caroline noted modestly, ‘many interesting discoveries were made’. At first she however had to remain at Rivers Street to oversee the selling off of the linen stock, and she missed the first few nights of observation in March. She subsequently recorded, with unusual care, that she did not return to New King Street until 21 March-as it turned out a historic absence.¹¹⁰

During these nights around the spring equinox Herschel was observing alone, and as well as continuing with their catalogue of double stars, he gave himself up to making drawings of Mars and Saturn. Possibly he was ranging more freely than usual, or possibly he was testing his ability to ‘sight read’ the sky. At all events, on Tuesday, 13 March 1781, slightly before midnight, Herschel spotted 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.

It also raises an intriguing question: how soon did Herschel know-or suspect-what he had discovered? It seems from his Observation Journal at the time, that what he thought he had found was a new comet. The following laconic account appears in his ‘First Observation Book’ for 12 and 13 March 1781

March 12 5.45 in the morning. Mars seems to be all over bright but the air is so frosty & undulating that it is possible there may be spots without my being able to distinguish them. 5.53 I am pretty sure there is no spot on Mars. The shadow of Saturn lays at the left upon the ring.

Tuesday March 13 Pollux is followed by 3 small stars at about 2’ and 3’ [minutes of arc] distance. Mars as usual. In the quartile near Zeta Tauri the lowest of two is a curious either nebulous star or perhaps a Comet. A small star follows the Comet at 2/3rds of the field’s distance.¹¹¹

There are no further remarks for these nights, and certainly no expression of excitement or anticipation. On the following night, Wednesday, 14 March, it was either cloudy, or Herschel did not bother to observe, for there is no entry. He may have been prevented by an official engagement to play the harpsichord at the Bath Theatre, or to rehearse oratorios with Caroline.¹¹² On 15 March there are short observations on Mars and Saturn, accompanied by some drawings of them made between 5 and 6 a.m., but nothing further about the ‘curious nebulous star or comet’. On Friday, 16 March there is again no entry. But Herschel may have been reflecting on his sightings, and talking to Caroline over the weekend, for finally, on the night of Saturday, 17 March there is the first clear sign that he was definitely in pursuit of the mysterious new object.

Saturday March 17 11pm. I looked for the Comet or Nebulous Star and found that it is a Comet, for it has changed its place. I took a superficial measure 1 rev, 6 parts and found also that the small star ran along the other [cross] wire…Position exactly measured 91′96…

Once Caroline had returned to New King Street on the twenty-first, there are regular entries in late March following the ‘comet’, and attempts to measure its diameter with William’s newly designed micrometer. For example, on 28 March the Observation Book reads: ‘7.25 pm. The diameter of the Comet is certainly increased, therefore it is approaching.’¹¹³ The increase in apparent size was a further indication of ‘proper motion’ and a solar orbit; and further proof that it could not possibly be a fixed star. But if it was a comet, there should be a slightly blurred, fiery outline and a distinct tail or ‘coma’. Here Herschel’s beautifully clear reflector images, even more than his high-magnification eyepieces, came into their own. In early April, some three weeks after his first sighting, Herschel made what seemed to be a definitive observation.

Friday April 6 I viewed the Comet with 460 [magnifications] pretty well defined, no appearance of any beard or tail. With 278 [magnifications] perfectly sharp and well defined.¹¹⁴

Though Herschel was scrupulously careful not to say so in his Observation Book, 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). He would name it patriotically after the Hanoverian king, ‘Georgium Sidus’ (‘George’s Star’), but it eventually became known to European astronomers as Uranus. ‘Urania’ was the goddess of astronomy, and the new planet was seen to mark a rebirth in her science.^♣

Yet there was no Eureka moment: quite the opposite. For the next few weeks there was a great deal of uncertainty about what sort of astronomical body Herschel had found. Nowhere does the word ‘planet’ appear in his Observation Journal for that spring of 1781, and there was no popular reporting of the news in the magazines. The following year, when the sensation was widely known, it would be very different, as Caroline remarked: ‘Since the discovery of the Georgium Sidus, I believe few men of learning or consequence left Bath before they had seen and conversed with its discoverer.’ But for the time being there were just endless measurements with the micrometer, ‘and a fire to be kept in, and a dish of Coffee during the long nights of watching’. She added wryly: ‘I undertook with pleasure what others might have thought a hardship.’¹¹⁵

On 22 March Herschel tentatively communicated his preliminary observations of ‘a Comet’ to William Watson, who passed them on to Nevil Maskelyne and Joseph Banks at the Royal Society.¹¹⁶ Maskelyne immediately contacted other European astronomers, notably Charles Messier in Paris, asking for their opinion.¹¹⁷ A week later Herschel followed this up with a direct report to the Royal Society, which was logged in the Society’s ‘Copy Journal Book’ for 2 April. Now he expressed barely muted excitement: ‘Saw the Diameter of the Comet extremely well defined and distinct; with several different powers thro’ my 20 foot Newtonian reflector. It was a glorious sight, as the Comet was placed among a great number of small fixt stars that seemed to attend it.’¹¹⁸

Remembering Herschel’s ‘lunacies’ of the previous year, Maskelyne was initially sceptical. He found great difficulty in even locating the new object with his own telescopes at Greenwich, a difficulty increased by Herschel’s inability to provide the conventional mathematical coordinates. At this stage Herschel located all his stars on hand-drawn star maps-what he called ‘an eye-draught’-an amateur technique that again visually recalls his familiarity with musical scores.¹¹⁹ It was not until 4 April that Maskelyne wrote cautiously to Watson (still not to Herschel directly) that he had finally found the new ‘star’, and observed that it had just discernible ‘motion’. However, he prudently, and not unreasonably, hedged his bets: ‘This [the motion] convinces me it is a comet or a planet, but very different from any comet I ever read any description of or saw. This seems a Comet of a new species, very like a fixt star; but perhaps there may be more of them.’ This safely covered all the options. He added a pointed postscript: ‘PS I think [Herschel] should give an account of his telescope, and micrometers.’¹²⁰

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. He was also aware that Banks regarded this as a crucial moment in his presidency, and in the fostering of good relations between the Royal Society and the Crown. King George III was particularly fascinated by stars, and particularly keen to outdo the French.

Maskelyne finally chose to act as a man of science: he went back to his own telescopes, and from 6 to 22 April made his own observations. He was, after all, acting precisely according to the motto of the Royal Society itself: Nullius in Verba-‘Nothing upon Another’s Word’. On 23 April he at last wrote directly to ‘Mr William Herschel, Musician, near the Circus, Bath’. He began prudently, but ended firmly.

Greenwich Royal Observatory, April 23, 1781

Sir, I am to acknowledge my obligation to you for the communication of your discovery of the present Comet, or planet.

I don’t know which to call it. It is as likely to be a regular planet moving in an orbit nearly circular round the sun, as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it…

This tipped the argument towards a planet, but was not a decisive opinion. Maskelyne then went into technical details about their respective telescopes-especially the need for ‘very firm stands’-and the difficulties of using micrometers to measure apparent changing diameters (and hence establish a possible planetary orbit): ‘If the light of the small planet is not still, & free from scintillations, it is impossible to prove it to have any other than a spurious diameter that may arise from the faults to which the best telescopes are subject.’ Nonetheless, he praised Herschel for making ‘very good observations’.

Finally, in his last paragraph, he committed himself. ‘On the 6th April I viewed the Comet with my 6 foot reflecting telescope and the greatest power 270, and saw it a very sensible size but not well defined. This however showed it to be a planet and not a fixt star, or of the same kind of fixt stars as to possessing native light with an insensible diameter. I am Sir, etc etc, N. Maskelyne.’¹²¹

Herschel had gained an invaluable ally. He immediately sent up a brief, masterly paper which was read at the Royal Society on 26 April. It was entitled simply ‘An Account of a Comet’, and was published in the Philosophical Transactions in June. He stated that ‘between ten and eleven in the evening’ of 13 March 1781 he had at once recognised a new object of ‘uncommon magnitude’ in Gemini, and immediately ‘suspected it to be a comet’. But from the account he then gave of its magnitude, clarity of outline and ‘proper motion’ it was clear that Herschel was now claiming that the ‘comet’ was really a new planet. Though, no doubt advised by Watson, he did not actually say so. To support this, he also claimed that the object remained perfectly round, without the least appearance of comet’s tail, when magnified 270, 460 and 932 times-the latter magnifications being far beyond what even Maskelyne’s Greenwich telescopes could achieve. All this naturally excited even more controversy than his moon paper, and some murmurs of dissent.¹²²

Maskelyne nevertheless stoutly confirmed his opinion to Banks that their dark horse, the ‘musician of Bath’, had made a revolutionary discovery, and had ‘much merit’. Yet he could not suppress a touch of rueful irony. ‘Mr Herschel is undoubtedly the most lucky of Astronomers in looking accidentally at the fixt stars with a 7 foot reflecting telescope magnifying 227 times to discover a comet of only 3’ [seconds of arc] diameter, which if he had magnified only 100 times he could not have known from a fixt star…Perhaps accident may do more for us than design could; and this makes one wish that the number of astronomers was multiplied in order to increase our chance of new discoveries.’¹²³ This suggestion that the discovery had been ‘accidental’, and that he had been ‘lucky’, was to grow increasingly disturbing to Herschel.¹²⁴

Maskelyne had made public his support of Herschel just in time. On 29 April Messier wrote directly to ‘Monsieur Hertsthel at Bath’ from Paris, congratulating him-‘this discovery does you much honour’-and giving his opinion that this was very likely to be the seventh planet in the solar system. Messier had himself, he said modestly, discovered no fewer than eighteen comets in his lifetime, and this resembled none of them: it was ‘a little planet with a diameter of 4 to 5 seconds, a whitish light like that of Jupiter, and having the appearance when seen with glasses of a star of the 6th magnitude’. He signed ‘with consideration and respect’ as ‘Astronomer to the Navy of France, of the Academy of Sciences, France’.

As Maskelyne and Banks were only too aware, Messier’s congratulations would soon carry the weight of the entire French Académie des Sciences.¹²⁵ Throughout the spring and summer months of 1781, more and more astronomers-in France, Britain, Germany, Italy and Sweden-observed the tiny moving speck, and took the view that it was indeed a planet circling in a massive ellipse beyond Saturn. These included Jacques Cassini, Henry Cavendish and Pierre Méchain. In October Anders Lexell, the celebrated Russian mathematician, wrote from his observatory far away in St Petersburg, sending a fully computed orbit and adding his congratulations. Using a series of parallax readings, he calculated that the planet was large and unbelievably remote, over sixteen times further from the sun than the earth, and twice as far out as Saturn. The size of the solar system had been doubled. Jérôme Lalande, who also computed the orbit, later said that this was the moment when the Académie des Sciences finally accepted the new planet-seven months after it had been sighted. Lalande himself suggested it should be christened ‘Herschel’.

It is suggestive that it was mathematical calculation, rather than astronomical observation, which finally convinced the scientific community that a seventh planet really did exist. One of the things Lexell’s calculation showed was that Herschel’s vivid impression that the planet was increasing in apparent diameter throughout March and April (and therefore approaching the earth) must have been the product of his growing concentration and excitement, since it was actually getting smaller and moving away. Lexell continued to work patiently for several years on his calculations, and later came up with the revised figure of 18.93 times the distance from the earth, impressively close to the modern computer-generated figure of 19.218. (In fact, as the planet’s orbit is elliptical not circular, the distance varies: at its closest it is 18.376 and at its furthest it is 20.083.)

In May, Watson proudly took Herschel up to London to meet his father Sir William, and to renew his now extremely cordial relations with Nevil Maskelyne. Together with the wealthy Deptford astronomer Alexander Aubert, they all dined with Sir Joseph Banks at the Mitre Club, the tavern much favoured by Dr Johnson. This was Herschel’s first meeting with the inner circle of British astronomers, and it was a great success. There was an air of suppressed triumph and excitement. Banks, in high spirits, seized his hand, congratulated him on ‘the great discovery’, and announced that he was to be elected to the Royal Society and awarded the Copley Gold Medal forthwith-within the next fortnight!¹²⁶ He claimed it as a decisive British victory over French astronomy, and the eminence of Messier, Pierre Laplace and Lalande, who had hitherto dominated European astronomy.

In fact Banks’s enthusiasm had rather got the better of him. The Copley Medal and the fellowship election had to go through the Society’s plodding bureaucratic procedures, which took another six months. Maskelyne used the interval to write warmly to Herschel in August: ‘I hope you will do the astronomical world the favour to give a name to your new planet, which is entirely your own, and which we are so much obliged to you for the discovery of.’¹²⁷

It was subsequently shown that ‘Georgium Sidus’ had actually been observed and recorded at least seventeen times between 1690 and 1781, and was even catalogued by Flamsteed. But it had always been dismissed as a minor ‘fixed’ star. It was only Herschel’s observational genius-and the quality of his seven-foot reflector-which identified it as a large, steadily moving body in regular orbit round the sun: a true planet. And it was Maskelyne who, by promptly supporting Herschel and bringing his observations to the attention of other leading European astronomers, confirmed the discovery and had it accepted by the scientific community at large. It later became clear that Uranus was a weird blue ice giant (not ‘little’ as Messier thought), twice the distance of Saturn, and taking 84.3 years to complete a solar orbit. It is the only planet in the solar system which is tilted ‘on its side’, so its axis of rotation, or spin, is horizontal to its solar orbit.^♣

In November Banks wrote a friendly and characteristically droll letter to Herschel, asking him for details of how he made the discovery that famous night, and all the difficulties ‘etc etc’ it caused him. He wanted to refer to these when presenting him to the assembled members of the Royal Society in London the following month: ‘Sir, The Council of the Royal Society have ordered their Annual Prize Medal to be presented to you in reward for your discovery of the new star. I must request that (as it is usual for me on that occasion to say something in commendation of the discovery) you will furnish me with such anecdotes of the difficulties you experienced etc etc…as you may think proper to assist me in giving due praise to your industry and ability.’

Banks, in high good humour, also enjoyed putting Herschel on his mettle. ‘Some of our astronomers here incline to the opinion that it is a Planet, and not a Comet. If you are of that opinion, it should forthwith be provided with a name, or our nimble neighbours, the French, will certainly save us the trouble of Baptizing it.’¹²⁸

Herschel, again advised by Watson, asked Banks if he could name the planet after the King, ‘Georgium Sidus’, a sound and self-effacing diplomatic stroke from a fellow Hanoverian.¹²⁹ But he was less easy about the continuing murmurs in some quarters of the Royal Society that his discovery had been in some sense ‘accidental’. This struck at his very notion of scientific method. He wrote insistently, even angrily, to Banks just before the ceremony on 19 November: ‘The new star could not have been found out even with the best telescopes had I not undertaken to examine every star in the heavens including such as are telescopic, to the amount of at least 8 or 10 thousand. I found it at the end of my second review after a number of observations…The discovery cannot be said to be owing to chance only it being almost impossible that such a star should escape my notice…The first moment I directed my telescope to the new star, I saw with a power of 227 that it differed sufficiently from other celestial bodies; and when I put on the higher powers of 460 and 932 was quite convinced it was not a fixt star.’¹³⁰

This claim was to become a point of honour with Herschel, often repeated. In September 1782 he wrote to Lalande in Paris, stating emphatically that the discovery ‘was not owing to chance’. Since he was embarked on a regular review of the sky, ‘it must sooner or later fall into my way, and as it was that day the turn of the stars in that neighbourhood to be examined, I could not very well overlook it’.¹³¹ The following year he wrote to the German astronomer Georg Christoph Lichtenberg at Göttingen, repeating that it was ‘not by accident’, and adding: ‘when I came to Astronomy as a branch of [mathematics] I resolved to take nothing upon trust but see with my own eyes all what other men had seen before’.¹³² Lichtenberg replied enthusiastically (in German): ‘Mein Gott! If I had only known, when I was for a few days in Bath in October 1775, that such a man lived there! As I am no friend of tea rooms, nor of cards or balls, I was much ennuyéd and spent my time at the top of the [cathedral] tower with a field glass…’

When he came to write an autobiographic sketch for his friend Dr Hutton in 1809, Herschel was more insistent than ever: ‘It has generally been supposed that it was a lucky accident which brought this star to my view; this is an evident mistake. In the regular manner I examined every star of the heavens, not only of that magnitude but many far inferior, it was that night its turn to be discovered. I had gradually perused the great Volume of the Author of Nature and was now come to the seventh Planet. Had business prevented me that evening, I must have found it the next, and the goodness of my telescope was such that I perceived its planetary disk as soon as I looked at it; and by application of my micrometer, I determined its motion in a few hours.’¹³³

This claim is not entirely borne out by his original Observation Journal. His first sweep or ‘review’ of double stars, begun in 1779, had not revealed the Georgium Sidus, so discovery on the second was not inevitable. Nor was recognition instant when it came. The journal reveals no precise Eureka ‘first moment’ on 13 March, only the hardening suspicion drawn out over five days to Saturday, 17 March that the strange body had ‘proper motion’, but was neither a ‘nebulous star’ nor a ‘comet’, and so was very probably a new planet. But it was Nevil Maskelyne who was the first to say so explicitly in writing, in April.

Nevertheless, Herschel’s discovery was an astonishing feat. It became his professional signature, and a historic moment for cosmology. It is hardly surprising that over the years he continued romantically to refine the story, and compressed his discovery into a single wondrous night, the inspired work of a glorious ‘few hours’. Caroline never commented on this, although it seems clear that she was present during the critical nights of measuring between 21 March and 6 April 1781. The effect of this account was to present an engagingly romantic image of science at work: the solitary man of genius pursuing the mysterious moment of revelation.

Joseph Banks’s presentation speech, when awarding the prestigious Copley Gold Medal for the best work in any scientific field during the year 1781, in front of the assembled Fellows of the Royal Society, was unreservedly complimentary to Herschel. The discovery of the new planet was the first great success of Banks’s new presidency. In his most expansive and jovial mood, he accordingly projected a visionary future for Herschel’s astronomy: ‘Your attention to the improvement of telescopes has already amply repaid the labour which you bestowed upon them; but the treasures of heaven are well known to be inexhaustible. Who can say but your new star, which exceeds Saturn in its distance from the sun, may exceed him as much in magnificence of attendance? Who can say what new rings, new satellites, or what other nameless and numberless phenomena remain behind, waiting to reward future industry?’¹³⁴

The award set the seal on Herschel’s reputation, and reignited the general fascination with astronomy. The discovery of the seventh planet began a revolution in the popular conception of cosmology. It was widely reported in the gazettes, journals and year books published in London, Paris and Berlin at the end of 1782. Yet although all orreries were instantly out of date, it took some time for Uranus to enter into the popular imagery and iconography of the solar system.

One of the best of the new wave of popular astronomy books was John Bonnycastle’s Introduction to Astronomy in Letters to his Pupil, which first appeared in 1786 (and went on to new expanded editions in 1788, 1811 and 1822). Bonnycastle gave the discovery of Uranus its own chapter: ‘Of all the discoveries in this science, none will be thought more singular than that which has lately been made by Dr Herschell…This is a Primary Planet belonging to the solar system, which till 13th of March 1781, when it was first seen by Dr Herschell, had escaped the observation of every other astronomer, both ancient and modern…’ Yet he still treated it as a puzzling novelty, its significance yet to be developed. ‘This discovery, which at first appears more curious than useful, may yet be of great service to astronomy…and may produce many new discoveries in the celestial regions, by which our knowledge of the heavenly bodies, and of the immutable laws that govern the universe, will become much more extended: which is the great object of the science…‘¹³⁵

Bonnycastle’s book was a thoroughly Romantic production, which included a good deal of ‘illustrative’ cosmological poetry from Milton, Dryden and Young. It also sported an engraved frontispiece by Henry Fuseli. This showed the goddess of astronomy, Urania, in a diaphanous observation-dress, pointing seductively to her new star while instructing a youthful male pupil. The publisher was Joseph Johnson of St Paul’s Churchyard, also the publisher of William Blake, William Godwin and Mary Wollstonecraft; and later of Wordsworth and Coleridge.

Bonnycastle was a great friend of the philosopher Godwin, and besides including poetry to illustrate his astronomical explanations, he considered the imaginative impact of the new astronomy. The ‘Babylonian’ writers of Egypt had increased the Biblical estimate of the earth’s age from 6,000 to 400,000 years, but Bonnycastle pointed out that ‘the best modern astronomers’ had increased this to ‘not less than 2 million years’. He thought that viewing the stars through a telescope both liberated the imagination and produced a certain kind of wonder, mixed with disabling awe or terror: ‘Astronomy has enlarged the sphere of our conceptions, and opened to us 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.’¹³⁶

Uranus slowly became a symbol of the new, pioneering discoveries of Romantic science. An unfathomably larger universe was steadily opening up, and this gradually transformed popular notions of the size and mystery of the world ‘beyond the heavens’. Indeed, the very terms ‘world’, ‘heaven’ and ‘universe’ began to change their meanings. It was the psychological breakthrough that Kant had predicted in his Universal Natural History and Theory of the Heavens back in 1755: ‘We may cherish the hope that new planets will perhaps yet be discovered beyond Saturn.’¹³⁷

Erasmus Darwin would eventually celebrate Herschel’s new astronomy in his poem The Botanic Garden (1791), notably in the spectacular opening section of Canto 1. The discovery of Uranus inspired Darwin to evoke many other possible ‘solar systems’, each with its own sun and planetary family, spontaneously exploding into being after an initial ‘big bang’. Here Darwin was using Newton’s celestial mechanics (based on Kepler’s three laws of planetary motion), but dramatising the new notion of an endless sequential creation as implied by Herschel. The creative cosmic force is ‘Love’ (as in the classical cosmology of Lucretius), while the Biblical God now seems content simply to initiate what is, in effect, a vast cosmological experiment, and then sit back as a passive observer.

When Love Divine, with brooding wings unfurl’d,

Call’d from the rude abyss the living World,

‘Let there be Light!’, proclaimed the Almighty Lord,

Astonish’d Chaos heard the potent word;

Through all his realms the kindling ether runs

And the mass starts into a million Suns.

Earths round each Sun with quick explosions burst,

And second Planets issue from the first;

Bend as they journey with projectile force,

In bright ellipses their reluctant course;

Orbs wheel in orbs, round centres centres roll,

And form, self-balanced, one revolving whole.

-Onward they move, amid their bright abode,

Space without bound, the bosom of their God!

To this shimmering and kinetic passage, which seems to anticipate in language the music of Haydn’s Creation (1796-98), Darwin added a long, admiring Note on ‘Mr Herschel’s sublime and curious account of the construction of the heavens’.^138♣

Astronomers from all over Europe (especially France, Germany and Sweden) began to write to Herschel in Bath, asking for details about his metal specula, his high-magnification eyepieces and his observational techniques. In England there continued to be much scepticism about both his abilities and his telescopes. His replies tended to be formal, but occasionally he relaxed a little with astronomers whom he trusted, and whose skills he admired. He light-heartedly described the pains he took to set up, tune and even ‘humour’ his telescopes. He gave them a life of their own, and implied that he treated them like so many concert prima donnas (perhaps remembering La Farinelli, who had saved him at the Pump Room). To Alexander Aubert in London he wrote one of his most whimsical accounts on 9 January 1782, when enclosing his new catalogue of double stars. ‘These instruments have played me so many tricks that I have at last found them out in many of their humours, and have made them confess to me what they would have concealed, if I had not with such perseverance and patience, courted them. I have tortured them with powers, flattered them with attendance to find out the critical moments when they would act, tried them with Specula of a short and long focus, a large aperture and a narrow one. It would be hard if they had not proved kind to me at last!’¹³⁹

It is striking how frequently he now compared the art of astronomical observation to learning and playing a musical instrument. To Aubert he wrote of the need to adjust each telescope individually and ‘to screw an instrument up to its utmost pitch. (As you are an Harmonist you will pardon the musical phrase.)’

Yet for some months Herschel had to continue to defend his telescopes against sceptics in the Royal Society. To the accusation that his discovery was by chance, they now added the implication that the huge powers of magnification he claimed were illusory. Particular scepticism was directed at his lens of 6,000 power, since it was calculated that a star so highly magnified would move through the viewing field of his telescope in ‘less than a second’, owing to the earth’s rotation. Therefore it would be quite impossible to observe. Herschel replied crisply that it took all of three seconds, and he could follow such a star very well.¹⁴⁰ But to William Watson he complained that his critics evidently intended to send him ‘to Bedlam’, and wrote defensively on 7 January 1782: ‘I do not suppose there are many persons who could even find a star with my [magnifying] power of 6,450; much less keep it if they had found it. Seeing is in some respects an art, which must be learnt. To make a person see with such a power is nearly the same as if I were asked to make him play one of Handel’s fugues upon the organ. Many a night have I been practising to see, and it would be strange if one did not acquire a certain dexterity by such constant practice.’¹⁴¹

Watson quietly kept Banks informed of the controversy, while Banks gently temporised, suggesting that perhaps the magnifications were slightly miscalculated, but supporting Herschel against his detractors. He sent smiling presidential greetings: ‘My best Compliments to Mr Herschell, with best wishes for the Sake of Science that his nights may be as Sleepless as he can wish them himself.’¹⁴²

Alexander Aubert now firmly took Herschel’s side. Thanking him for the catalogue of double stars, he remarked appreciatively on all the trouble Herschel had taken: ‘but trouble is nothing to you, and the least thing we can do in return is to…convince the world that though your discoveries are wonderful, they are not imaginary…Your great power of 6450 continues to astonish, your micrometer also…Go on, my dear Sir, with courage, mind not a few barking, jealous puppies; a little time will clear up the matter and if it lays in my power you shall not be sent to Bedlam alone, for I am much inclined to be one of the party.’¹⁴³

Herschel’s next destination, as it turned out, was not Bedlam but Windsor. King George III, advised by the Astronomer Royal and the President of the Royal Society, had chosen to ignore these controversies. He summoned Herschel to court to congratulate him, but asked Banks and Maskelyne to make an independent trial of the now celebrated sevenfoot telescope at the Greenwich Observatory. On 8 May Herschel left for London, his precious telescope and folding stand perilously packed into a mahogany travel-box (’to be screwed together on the spot where wanted’), accompanied by a hastily assembled trunk of equipment including his large Flamsteed atlas (marked up by Caroline), his new catalogue of double stars (similarly written up by Caroline), ‘micrometers, tables, etc’, and rather makeshift court dress.¹⁴⁴

At Greenwich, Maskelyne was stunned by the superior quality and light-gathering power of Herschel’s ‘home made’ mirrors. He immediately recognised that they were far more powerful than any of the official observatory telescopes, and probably than any other telescope in Europe. Maskelyne, reputed to be a jealous and illiberal man because of his supposed ill-treatment of the watchmaker John Harrison, behaved with great forthrightness and generosity to Herschel.

On 3 June 1782 Herschel wrote exuberantly to Caroline, casting aside his usual circumspect tone: ‘Dear Lina…The last two nights I have been star-gazing at Greenwich with Dr Maskelyne & Mr Aubert. We have compared our telescopes together and mine was found very superior to any at the Royal Observatory. Double stars they could not see with their instruments I had the pleasure to show them very plainly, and my [folding stand] mechanism so much approved of that Dr Maskelyne has already ordered a model to be taken from mine; and a stand to be made by it for his reflector. He is however now so much out of love with his instrument [a six-foot Newtonian] that he begins to doubt whether it deserves a new stand.’¹⁴⁵

Banks (who had learned much about royal decorum since Tahiti) now knew that it was the perfect moment to introduce Herschel formally to the King at Windsor in May 1782. The meeting between the two Hanoverians (commoner and king, but both firmly speaking English) was a great success. Members of the King’s Hanoverian entourage had already heard of the Herschel brothers as talented musicians, and His Majesty was intrigued by the change in métier.¹⁴⁶ King George, not yet mad, was renowned for his aphoristic remarks to his more talented subjects. To Edward Gibbon, for example, still deep in his six-volume history The Decline and Fall of the Roman Empire, he had observed archly: ‘Scribble, scribble, scribble, eh, Mr Gibbon?’ It was said that the King now murmured to Banks: ‘Herschel should not sacrifice his valuable time to crotchets and quavers.’¹⁴⁷

Herschel wrote swiftly to Caroline, with a note of growing excitement that had never previously appeared in his letters. ‘Among Opticians and Astronomers nothing is now talked of but what they call my great discoveries. Alas! This shows how far they are behind, when such trifles as I have seen and done are called great. Let me but get at it again! I will make such telescopes & see such things-that is, I will endeavour to do so.’¹⁴⁸ In a later note, again using her intimate diminutive name, he added: ‘You see Lina I tell you all these things, you know vanity is not my foible therefore I need not fear your Censure.’¹⁴⁹ He would not have feared his sister’s censure a decade before.

Banks was determined to find his new astronomical protégé a salary, and if possible a suitable place. This required some diplomacy, as university professorships were for mathematicians, the post of Astronomer Royal was evidently taken, and the new post of Royal Astronomer at Kew Gardens had recently been promised to another-‘a devil of a pity’. With Banks’s diplomatic nudging, the King agreed that Herschel should give up teaching music in Bath, and move to a house near Windsor, to concentrate entirely on astronomy. To achieve this, His Majesty would be pleased to create a new official post, appointing Herschel as the King’s Personal Astronomer at Windsor on a salary of £200 per annum. (This was not particularly generous, but then the Astronomer Royal received only £300.) At the age of forty-three, Herschel’s second career had burst into life.

After the very briefest consultation, Herschel, Caroline and their brother Alexander moved on 31 July 1782 to a large, sprawling house in the village of Datchet, positioned deep in the countryside between Slough and Windsor, just south of the river Thames. The house had large grass plots suitable for erecting telescopes, and several stables and outbuildings for the furnaces and the grinding and polishing equipment. An old laundry could be converted into an observation building. But the house itself had not been inhabited for several years, and was cold and damp. Caroline set about the huge task of cleaning and repairing.¹⁵⁰

Almost immediately Herschel was commanded to bring his famous seven-foot telescope to Windsor, where it was reassembled on the terrace for everyone to view the planets. Herschel was a particular success with the three teenaged royal princesses, Charlotte, Augusta and Elizabeth. On one cloudy evening (it being an English summer) when viewing was impossible, he had the inspired idea of constructing pasteboard models of Jupiter and its four moons, and Saturn and its rings, and hanging them-illuminated by candles-from a distant garden wall on the Windsor estate. These were meticulously prepared beforehand. By ingeniously focusing down the seven-foot, he was able to show these models to the three young girls through the telescope, an early form of outdoor planetarium.¹⁵¹

Many other children of the new generation also grew up understanding the cosmos in a new way. Discovering the stars became a particular and special moment of self-discovery. The poet Coleridge remembered being taken out at night into the fields by his beloved father, the vicar and schoolmaster of Ottery St Mary in Devon, in the winter of 1781 to be shown the night sky. Coleridge was only eight, but he never forgot it. Perhaps the Reverend John Coleridge, a great follower of the monthly magazines (to which he sometimes contributed learned articles on Latin grammar), had recently read of Georgium Sidus. At all events, Coleridge treasured the memory of his father’s eager demonstration of the stars and planets overhead, and the possibility of other worlds: ‘I remember, that at eight years old I walked with him one evening from a farmer’s house, a mile from Ottery-& he told me the names of the stars-and how Jupiter was a thousand times larger than our world-and that the other twinkling stars were Suns that had worlds rolling round them-& when I came home, he showed me how they rolled round. I heard him with profound delight & admiration; but without the least mixture of Wonder or incredulity. For from my early reading of Faery Tales, & Genii etc etc-my mind had been habituated to the Vast.’¹⁵²

Such a huge, starlit prospect, inhabited by giant planets and remote classical gods, might have puzzled or alarmed a normal eight-year-old. But the striking thing is that Coleridge, who wrote many letters about his childhood and always remembered it acutely, said he felt no surprise or disbelief at all-‘not the least mixture of Wonder or incredulity’-about this revelation of the enormous scale of the universe. He felt himself already tuned to the size and mystery of the new cosmos. His Romantic sensibility-even at the age of eight-already inhabited the infinite and the inexplicable. Cosmological imagery, and especially the symbolic movement of the stars and the moon, entered deeply into his early poetry, and in a sense it came to rule the world of the Ancient Mariner and his ship.

The moving Moon went up the sky,

And nowhere did abide;

Softly she was going up,

And a star or two beside.

Her beams bemocked the sultry main,

Like April hoar-frost spread,

But where the ship’s huge shadow lay,

The charmed water burnt alway

A still and awful red.¹⁵³

The prose gloss that Coleridge added to this passage almost twenty years later (1817) takes on a new resonance when compared with what we now know of Herschel’s long nights of lunar observation:

In his loneliness and fixedness he yearneth towards the journeying Moon, and the stars that still sojourn, yet still move onward; and every where the blue sky belongs to them, and is their appointed rest, and their native country and their own natural homes, which they enter unannounced, as Lords that are certainly expected and yet there is silent joy at their arrival.^♣

The young John Keats remembered an organised game at his school in Enfield, in which all 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). Unlike Newton’s perfect brassy clockwork mechanism, this schoolboy universe-complete with straying comets-was a gloriously chaotic ‘human orrery’.

Keats did not recall the exact details, but one may imagine seven senior boy-planets running round the central sun, while themselves being circled by smaller sprinting moons (perhaps girls), and the whole frequently disrupted by rebel comets and meteors flying across their orbits. Keats was later awarded Bonnycastle’s Introduction to Astronomy as a senior 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’.¹⁵⁴