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how to define a planet: the problematic case of Pluto

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Pluto, with its ‘heart-shaped’ area known as Sputnik Planitia, imaged by New Horizons, July 14 2015

A while back I listened to a podcast from Point of Inquiry, in which two planetary scientists, Alan Stern and David Grinspoon, involved in NASA’s New Horizons mission to Pluto, were separately interviewed, and were inevitably asked about Pluto’s demotion from planet status. Having not followed this issue, I was surprised at the response. So it’s time to take a closer look.

Of course I should be writing ecstatically about the New Horizons mission, not to mention those of Juno, Cassini, Mars’ Curiosity and so forth, and hopefully that will come, but the controversy about Pluto immediately struck me, as I thought, in my naïveté, that its demotion was a consensual thing amongst astronomers, with only the ignoroscenti (my neologism) left to mourn the fact (not that I mourned it particularly – Pluto still existed after all, and it didn’t care a jot what we thought of it).

Pluto, discovered by Clyde Tombaugh in 1930, was accepted as the ninth and final planet in our solar system for decades until the nineties, when another Kuiper belt object was discovered (besides Charon, Pluto’s large moon), and the Kuiper belt itself became a thing, in fact a massive thing, far bigger than the ‘familiar’ asteroid belt between Mars and Jupiter. We now know of more than 1000 kuiper belt objects, with at least 100,000 believed to exist. The Kuiper belt is widely spread out from the orbit of Neptune, and though Pluto is its largest and brightest object, it’s not the most massive. Presumably it’s for this reason that Pluto was demoted – what with the scattered disc and the Oort cloud there seemed to suddenly be a host of objects that could be included as planets, so it was thought better to exclude Pluto, or to demote it to dwarf planet status, presumably along with other assorted Kuiper belt objects (KBOs), rocks and iceballs that were worthy of the designation. That seemed okay to my thoughtless mind, but here’s what Alan Stern had to say on the subject:

Well, you know, we don’t really honour that classification in planetary science, that was really done by a group of different astronomers who don’t know much about planets. Let me give you a technical term, we call it BS. You know what BS stands for don’t you? Bad Science. Now you wouldn’t ask a podiatrist, a foot doctor, to help you if you had a cardiovascular problem with your heart, that’d be the wrong expertise, though they’re both doctors you’d be going for a cardiologist. And if you had a real estate problem you probably wouldn’t go to a divorce attorney, even though they’re both attorneys. In the space field we have many professions, we have engineering professions, we have many different scientific specialties, etc. Astronomers really don’t know much about planets any more than I’m an expert in black holes in faraway galaxies. They had a little meeting in 2006, they were worried that school children would have to memorise the names of too many planets, so they wrote a definition that limited the number of planets to eight. Now, right after that, Ira Flatow called me up on Science Friday and said, would you debate Mike Brown, who was one of the proponents of ‘let’s limit the planets to eight’, and I said, sure, and we got on the phone and it’s Science Friday live, and Mike Brown makes his case and says, ‘look we just can’t have 50 planets, it’s too many to remember.’ Now, I found that anti-scientific, it seems like engineering the definition, versus letting it inform you, but Ira said, Alan what’d you think, ‘can’t have 50 planets’, what d’you say back to MIke? I said, ‘well if you can’t have 50 planets then we’re probably going to have to go back to eight states, I guess’. And he was speechless…

I love that story – though no doubt Mike Brown would’ve told a different one. So let’s turn Stern’s objection into an inquiry. Was it scientifically correct/accurate/fair to reclassify Pluto as a dwarf/minor planet?

Happily I just happened to listen to a podcast of the Skeptics’ Guide a few days later, which has led me to a more detailed piece on Steven Novella’s Neurologica blog on the Pluto controversy. Apparently, in the above-mentioned 2006 meeting they decided that to be classified as a planet, a body in our solar system should meet 3 criteria:

  • it has to orbit the sun
  • it has to be spheroid (i.e. have the mass to be so, due to its gravity),
  • it must have cleared its orbit of other objects.

Now this third criteria immediately seems the dodgiest, as it sounds like it’s designed to eliminate any KBOs. And how do we know an orbit is cleared? After all, one day, a comet or asteroid may strike us, because our orbits have coincided this time around. And why is that third criterion even important?

Novella cites a recent paper by planetary scientist Phillip Metzger who argues that the third criterion is invalid and that nothing about a body’s orbit should be in the definition since orbits can alter due to external influences. Only characteristics intrinsic to the body should be included in the definition. This would essentially leave one criterion standing – that of sphericity. And even then, how sphere-like does a planet have to be? Another ‘problem’ with Metzger’s definition is that it would include moons, such as our own, and many others. Novella has his own classifying suggestion, which sounds promising to me:

We keep criteria “a” and “b” and drop “c”. However, we add that the object must not be in a subservient orbit around a larger object. What does that mean? If two objects, like the Earth and Moon, are in orbit around each other, and the center of gravity (barycenter) lies beneath the surface of one of the bodies, then the smaller object will be said to orbit the larger object, and is a moon. Therefore Europa, which is large enough by itself to be a planet, would instead be considered a moon because it orbits Jupiter.

I need to further explain the term ‘barycentre’, for my own sake. Think of two bodies in gravitational relationship to each other. Inevitably, one of them will be more massive, and will exert a greater gravitational force. An obvious case is the Earth and the Moon. Between the two there is a point, the ‘centre of gravity’, or barycentre,  around which the two bodies revolve, but because the Earth is a lot more massive that the Moon and they’re relatively close to each other, that barycentre is actually close enough to the Earth’s centre to be within the mass of the Earth, with the result that only the moon revolves. The Earth, though, is very much affected by the Moon’s gravitational field, which causes a slight wobble as well as tidal effects on the Earth’s surface. 

Interestingly, Novella’s reclassification would include Charon, Pluto’s ‘moon’, as a planet (as well as Pluto of course) because its size relative to Pluto puts the barycentre at a point between the two bodies, rather than within Pluto. So Pluto-Charon would be reclassified as a binary-planet system. It would also promote Ceres, in the asteroid belt, and Eris and Makemake, two recently discovered Kuiper belt objects, to planetary status. That takes the current eight up to thirteen, with others yet to be discovered. 

It’s unlikely of course that the astronomical overlords who reclassified Pluto would be swayed by any mere outsider’s view, however well-reasoned, but this examination of the issue is a reminder of just how dubious the reasoning of ‘experts’ can be, and how important it is to question that reasoning. Size apparently does matter to these guys, but this new category of ‘dwarf’ or ‘minor’ planet seems inherently unstable, and will probably become even more so as the number of discovered exoplanets increases. Will it be mass or volume that’s the decider, and what will be the mass or volume that decides? And does it really matter? It’s only nomenclature after all. And yet… The difference between an asteroid and a comet is important, is it not? And so is the difference between a planet and an asteroid. And so is the difference between a moon and a planet. And so… is it not? 

Written by stewart henderson

October 14, 2018 at 1:09 pm

exoplanets – an introduction of sorts

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Jacinta: So do you think we’ve hauled ourselves out of ignorance sufficiently to have a halfway stimulating discussion on exoplanets?

Canto: I think we should try, since it’s one of the most exciting and rapidly developing fields of inquiry at the moment.

Jacinta: And that’s saying something, what with microbiomes, homo naledi, nanobots and quantum biology…

Canto: Yes, enough to keep us chatting semi-ignorantly to the end of days. But let’s try to enlighten each other on exoplanets…

Jacinta: Extra solar planets, planets orbiting other stars, the first of which was discovered just over 20 years ago, and now, thanks largely to the Kepler Space Observatory, we’ve discovered thousands, and future missions, using TESS and the James Webb telescope, will uncover megatonnes more.

Canto: Yes, and you know, about the Kepler scope, l was blown away – this might be veering off topic a bit, but I was blown away in researching this by the fact that Kepler orbits the sun. I mean, I knew it was a space telescope, but I just assumed it was in orbit around earth, probably at a great distance to avoid interference from our atmosphere, but that we can position satellites in orbit around the sun, that really sort of stunned me, more I think than the exoplanet discoveries. Am I being naive?

Jacinta: No, not at all. Well, yes and no. Everything is stunning if you haven’t followed the incremental steps along the knowledge pathway. I mean, if you think, hey the sun’s a way away, and it’s really big and dangerous, best not go there, or something like that, you might be shocked, but think about it, we’ve been sending satellites around the earth for a long time now, and we know how to do it because we know about earth’s gravitational field and can calculate precisely how to harness it for satellite navigation. We’ve currently got a couple of thousand human-made satellites orbiting the earth and trying more or less successfully to avoid colliding with each other. So the sun also has a gravitational field and we’ve known the mathematics of gravitational fields since Newton. It’s the same formula for a star, a planet or whatever, all you need to know is its mass and its radius. And look at all the natural objects orbiting the sun without a problem. Can’t be that hard.

Canto: Okay… so how do we know the mass of the sun? Okay, forget it, let’s get back to exoplanets. What’s the big fuss here? Why are we so dead keen on exploring exoplanets?

Jacinta: Well the most obvious reason for the fuss is SETI, the search for extra-terrestrial intelligence, but to me it’s just satisfying a general curiosity, or you might say a many-faceted curiosity. And it’s all about us mostly. For example, is the solar system that we inhabit typical? We’ve mostly thought it was but we didn’t have anything to compare it with, but now we’re discovering all sorts of weird and wonderful planetary systems, and star systems, with gas giants like Jupiter orbiting incredibly close to their stars – it’s completely overturned our understanding of how planets exist and are formed, and that’s fantastically exciting.

Canto: So you say we discovered the first exoplanet about 20 years ago, and now we know about thousands – that’s a pretty huge expansion of our knowledge, so how come things have changed so fast? You’ve mentioned new technologies, new space probes, why have they suddenly become so successful?

Jacinta: Well I suppose it’s been a convergence of developments, but let’s go back to that first discovery, back in 1992. Two planets, the first ever discovered, were found orbiting a pulsar – a rapidly rotating neutron star. First discovery, first surprise. Pulsars with planets orbiting them, who would’ve thought? Pulsars are the remnants of supernovae – how could planets have survived that? But that first discovery was largely a consequence of our ability to measure, and the fact that pulsars pulse with extreme regularity. Any anomaly in the pulsing would be cause for further investigation, and that’s how the planets were found, and later independently confirmed. Now this was big news, in a field that was already becoming alert to the possibility of exoplanets, so you could say it opened the floodgates.

Canto: Really? But they didn’t discover any more for two or three years.

Jacinta: Well, okay it opened the gates but it didn’t start the flood, that really happened with the second discovery, the first discovery of a planet orbiting a main-sequence star like ours.

Canto: Main sequence? Please explain?

Jacinta: Well these are stars in a stable state, a state of balance or equilibrium, fusioning hydrogen – basically stars not too different from our own, within much the same range in terms of mass and luminosity. So 51 pegasus b was the first planet to be discovered by the radial velocity method, and radial velocity means the speed at which a star is moving towards or away from us. We can measure this, and whether the star is accelerating or decelerating in its movement, by means of the Doppler effect – waves bunch up when the object emitting them is moving towards us, they spread out when the object is receding from us, and the degree of the bunching or the spreading is a measure of their speed and whether it’s accelerating or decelerating. Now we can measure this with extreme accuracy using spectrometers, and that includes any perturbations in the star’s movement caused by orbiting bodies. That’s how 51 pegasus b was discovered.

Canto: So… how long have we had these spectrometers? Were they first developed in the nineties, or to the level of accuracy that they could detect these perturbations?

Jacinta: Well I don’t have a precise answer to that apart from the general observation that spectroscopes are getting better, and more carefully targeted for specific purposes. The French ELODIE spectrograph, for example, which was used to find 51 pegasus b, was first deployed in 1993 specifically for exoplanet searching, and since then it’s been replaced by another improved instrument, but of the same type. So it’s a kind of non-vicious circle, research leads to new technology which leads to new research and so on.


Canto: So – we’ve gotten very good at measuring perturbations in a star’s regular movements…

Jacinta: Regular perturbations.

Canto: And we know somehow that these are caused by planets orbiting around them? How do we know this?

Jacinta: Well we will know from the size of the perturbation and its regularity that it’s an orbiting body, and we know it’s not a star because it’s not emitting any light (though it may be a low-mass star whose light isn’t easily separated from its parent star). We also know – we knew from the results that it was a massive planet orbiting very close to its star – a hot Jupiter as they  call it. And that was another surprise, but we’ve developed different techniques for discovering these things and we often use them to back each other up, to confirm or disconfirm previous findings. The ELODIE observation of 51 pegasus b was confirmed within a week of its announcement by another instrument, the Hamilton spectrograph in California. So there’s a lot of confirmation going on to weed out false positives.

Canto: So radial velocity is one technique, and obviously a very successful one as it got everyone excited about exoplanets, but what others are there, and which are the most successful and promising?

Jacinta: Well the radial velocity method was initially the most successful as you say, and hundreds of exoplanets have been discovered that way, but this method actually led to a kind of bias in the findings, because it was only able to detect perturbations above a certain level, so it was best for finding large planets close to their stars. But of course that was good too because we had never imagined that large gassy planets could exist so close to their stars. It’s opened up the whole field of planet formation. Then again, if the main aim is to find earth-like planets, this method is less effective than other methods. So let’s move on to the Kepler project. Kepler was launched in 2009, and since then you could say it has blitzed the field in terms of exoplanet detection. It uses transit photometry, which means that it measures the dimming of the light from a star when an orbiting planet passes between it and the Kepler detector.

Canto: So I get the idea of transit, as in the transit of venus, which we can see pretty clearly, but it’s amazing that we can detect transiting planets attached to stars so many light years away.

Jacinta: Well this is how we’ve expanded our world, from the infinitesimally small to the unfathomably large, from multiple billions of years to femtoseconds and beyond, through continuously refining technology, but let’s get back to Kepler. It orbits around the sun, and has collected data from around 145,000 main sequence stars in a fixed field of view – stars that are generally around the same distance from that dirty big black hole at the centre of our galaxy as our sun is.

Canto: Is that significant – that we’re focusing on stars in that range?

Jacinta: Apparently so, at least according to the Rare Earth Hypothesis, which puts all sorts of unimaginative limits on the likelihood of earth-like planets, IMHO, but no matter, it’s still a vast selection of stars, and we’ve reaped a grand harvest of planets from them – some 3000-odd, with over 1000 confirmed.

Canto: So… promising earth-like planets?

Jacinta: Yes, but I must point out that earth-like planets are difficult to detect. You see, Kepler was a kind of experiment, and we’ve learned from it, so that our next project will be much improved. For various reasons due to the photometric precision of the instrument, and inaccurate estimates of the variability of the stars in the field of view, we found that we needed to observe more transits to be sure we’d detected something. In other words we needed a longer mission than we’d planned for. And of course, Kepler has suffered serious technical problems, especially the failure of two reaction wheels, which have affected our ability to repoint the instrument. Having said that, we’ve been more than happy with its success.

Canto: Okay I just want to talk about these exoplanets. Can you summarise the most interesting discoveries?

Jacinta: Well, Kepler has certainly corrected the view we might’ve gotten from the earlier radial velocity method that large Jupiter-like planets are more common than smaller ones. We’ve had a number of reports from the Kepler group over the years, and over time they’ve adjusted downwards the average mass of the planets detected. And yes, they’ve discovered a number of planets in the ‘habzone’ as they call it. But that’s not all – only this year NASA confirmed the existence of five rocky planets, smaller than earth, orbiting a star that’s over 11 billion years old. I’m just trying to give you an idea of the explosion of findings, whether or not these planets contain life. And we’ve only just begun our hunt, and the refinement of instruments. It’s surely a great time to study astrophysics. It’s not just SETI, it’s about the incredible diversity of star systems, and working out where we fit into all this diversity.


Canto: Okay, I can see this an appropriately massive subject. Maybe we can revisit it from time to time?

Jacinta: Absolutely.

Some very useful sites:


Written by stewart henderson

October 30, 2015 at 10:05 pm

what does curiosity actually mean?

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Robert Hooke, star of the early Royal Society

Robert Hooke, star of the early Royal Society

You might say that Philip Ball has performed a curious task with his book, Curiosity. He’s taken this term, which we moderns might take for granted, and examined what intellectuals and the public have made of it down through the ages – with a particular focus on that wobbly symbol of the seventeenth century British scientific enlightenment, the Royal Society. I’ve been spending a bit of time in the seventeenth century lately, what with Dava Sobel’s book on the struggle to measure longitude, Matthew Cobb’s book on the untangling of the problem of eggs and sperm and conception, not to mention Bill Bryson’s lively treatment of Hooke, Leeuwenhoek and cells and protozoa in A Short History of Nearly Everything.

That century, with some of its most interesting actors, including Francis Bacon, René Descartes, William Harvey, Jan Swammerdam, Nicolas Steno, Johann Komensky (aka Comenius), Samuel Butler, Thomas Hobbes, Robert Hooke, Robert Boyle, Antonie van Leeuwenhoek, Thomas Shadwell, Margaret Cavendish and Isaac Newton, represented a great testing period for science and its reception by the public. Curiosity has always had its enemies, and still does, as evidenced by some Papal pronouncements of recent years, but in earlier, more universally religious times, knowledge and its pursuit were treated with great wariness and suspicion, a suspicion sanctioned by the Biblical tale of the fall. The Catholic Church had risen to a position of great power in the west, though the revolting Lutherans, Anglicans, Calvinists and their ilk had spoiled the party somewhat, and England in particular, having grown in pride and prosperity during the Elizabethan period, was flexing its muscles and exercising its grey matter in exciting new ways. The sense of renovation was captured by  the versatile Bacon, with works like the Novum Organum (New Method), The New Atlantis and The Advancement of Learning.

In the past I’ve described curiosity and scepticism as the twin pillars of the scientific mindset, but they’re really more like a pair of essential forces that interact and modify each other. Scepticism without curiosity is just pure negativity and nihilism, curiosity without scepticism is directionless and naive.

But perhaps that’s overly glib. What, if any, are the limits of curiosity, and when is it a bad thing? It killed the cat, after all.

The word derives from the Latin ‘cura’, meaning care. Think of the word ‘curator’. However, if you think of one of the most curious works of the ancients, Pliny the Elder’s Natural History, you’d have to say, from a modern perspective, that little care was taken to separate truth from fiction in his massive and sometimes bizarre collection of curios. This sort of unfiltered inclusivity in collecting ‘facts’ and stories goes back at least to Herodotus, the ‘father of lies’ as well as of history, and it goes forward to medieval bestiaries and herbaria. These collections of the weird and wonderful were, of course, not intended to be scientific in the modern sense. The term ‘science’ wasn’t in currency and no clear scientific methodologies had been elaborated. As to curiosity, it certainly wasn’t a fixed term, and after the political establishment of Christianity, it was more often than not seen in a negative light. ‘We want no curious disputation after possessing [i.e. accepting the truth of] Jesus Christ’, wrote Tertullian in the early Christian days. Another early Christian, Lactantius [c240-c320], explained that the reason Adam and Eve were created last was so that they’d remain forever ignorant of how their god created everything else. That was how it was intended to be. Modern creationists follow this tradition – God did it, we don’t know how and we don’t really care.

Fast forward to Francis Bacon, who still, in the early 17th century, had to contend with the view of curiosity as a sinful extravagance, a view that had dominated Europe for almost a millennium and a half. Bacon had quite a pragmatic, almost business-like view of curiosity as a tool to benefit humanity. The ‘cabinet of curiosities’ was becoming well established in his time, and Bacon advised all monarchs, indeed all rich and powerful men, to maintain one, well sorted and labelled, as if to do so would be magically empowering. The problem with these cabinets, though, was that there was little understanding about the relations between entities and articles. That’s to say, there was little that was modernly scientific about them. Their objects were largely unrelated rarities and oddities, having only one thing in common, that they were ‘curious’. Bacon recognised that this wouldn’t quite do, and tried to point a way forward. He didn’t entirely succeed, but – small steps.

Ball’s book is at pains to correct, or at least provide nuance to, the standard view of Bacon as initiator of and father-figure to the British scientific enlightenment. In fact, Bacon may have been a Rosicrucian, and his utopian New Atlantis describes a more or less priestly caste of technical experts, living and working in Solomon’s House, and keeping their arts and knowledge largely under wraps, like the alchemists and mages of earlier generations. Bacon, with his government connections and his obvious ambition to be benefited by as well as benefiting the state, was concerned to harness knowledge to productivity and profit, and those who see science largely as a coercion of nature have cursed him for it ever since. Mining and metallurgy, engineering and manufacturing were his first subjects, but he also imagined great changes in agriculture – the breeding of plants, fruits and flowers, as well as animals, to create ‘super-organisms’, in and out of season, for our benefit and delight. The art and science of the kitchens of Solomon’s House produces superior dishes, as well as wines and other beverages, and printing and textiles have advanced greatly, with new fabrics, papers, dyes and machinery. Even the weather is subject to manipulation, with rain, snow and sunshine under the control of the savants. The details of all these advancements are kept vague of course, (and here’s where Bacon’s insistence on ‘secret knowledge’ plays to his advantage, a point not sufficiently noted by Ball in his need to connect Bacon with the the alchemist-magicians of the past) but what is represented here is promise, a faith in human ingenuity to improve on the products of the natural world.

In focusing on all these benefits, Bacon manages largely to sidestep the religious aversion to curiosity as a form of intellectual avarice. However, Bacon and his more curious compatriots were never too far from the magical dark arts. Few intellectuals of this period, for example, would have dismissed alchemy out of hand, in spite of Chaucer’s delicious mockery of it over 200 years before, or Ben Jonson’s more contemporaneous take in The Alchemist. What differentiated Bacon was an interest in system, however vaguely adumbrated, and a harnessing of this system to the interests of the state.

Bacon tried to interest James I in a state sponsored proto-scientific institution, but this got nowhere, largely because he couldn’t devise anything like a practical program for such an entity, but a generation or two after his death, after a civil war, a brief republic and a restoration, the Royal Society was formed under the more or less indifferent patronage of Charles II. Bacon was seen as its guiding spirit, and there was an expectation, or hope, that its members would be virtuosi, a term then in currency. As Ball explains:

The virtuoso was ‘a rational artist in all things’… meaning the arts as well as the sciences, pursued methodically with a scientist’s understanding of perspective, anatomy and so forth. (It is after all in the arts that the epithet ‘virtuoso’ survives today.) The virtuoso was permitted, indeed expected, to indulge pure curiosity: to pry into any aspect of nature or art, no matter how trivial, for the sake of knowing. There was no sense that this impulse need be harnessed and disciplined by anything resembling a systematic program, or by an attempt to generalise from particulars to overarching theories.

Charles II, in spite of having some scientific pretensions, paid scant attention to his own Society, and neglected to fund it. What was perhaps worse for the Society was his amused approval of a hit play of the time, Thomas Shadwell’s The Virtuoso, which satirized the Society through its central character, Sir Nicholas Gimcrack. The play, as well as many criticisms of the Society’s practices by the likes of the philosopher Thomas Hobbes and the aristocratic Margaret Cavendish (Duchess of Newcastle-upon-Tyne), presented another kind of negativity vis-a-vis unbridled curiosity, more modern, if not more pointed than the old religious objections.

The play-goer first encounters Sir Nicholas Gimcrack lying on a table making swimming motions. He tells his visitors that he’s learning to swim, but they are dubious about his method. His response:

I content myself with the speculative part of swimming; I care not for the practick. I seldom bring anything to use; tis not my way. Knowledge is my ultimate end.

This was the updated criticism. Pointless observations and experiments, leading nowhere and of no practical use. Gimcrack appears to have been based on Robert Hooke, one of the Royal Society’s most brilliant members, who was suitably enraged on viewing the play. Shadwell mocked Hooke’s prized invention, the air pump, intended to create a vacuum for the purpose of observing objects inserted into it, and he presented a jaundiced view of Gimcrack, through the dialogue of his niece, as ‘a sot that has spent two thousand pounds in microscopes to find out the nature of eels in vinegar, mites in a cheese, and the blue of plums.’ These were all examined in Hooke’s ground-breaking and breath-taking work Micrographia.

Most of Shadwell’s mockery hasn’t stood the test of time, but he was far from the only one who targeted the practices and the approach of the Society and of ‘virtuosi’, sometimes with humour, sometimes with indignation. Their criticisms are worth examining, both for what they reveal of the era, and for their occasional relevance today. Many of them seem totally misplaced – mocking the ‘weighing of air’, which they naturally saw as the weighing of nothing, or the examining, through the newish tool the microscope, of a gnat’s leg. It should be recalled that Hooke, through his microscopic investigations, was the first to highlight and to name the individual cell. Yet it was a common criticism of the era, due largely to the ignorance of the interconnectedness of all things that the scientifically literate now take for granted, that these explorations were simply time-wasting dilettantism. The philosophical curmudgeon Thomas Hobbes, for example, firmly believed that experiments couldn’t produce significant truths about the world. It seems that the general public, who didn’t have access to such things, saw microscopes and telescopes as magical devices which didn’t so much reveal new worlds as to create them. If they couldn’t be verified with one’s own eyes, how could these visions be trusted? And there was the old religious argument that we weren’t meant to see them, that we should keep to our god-given limitations.

Generally speaking, as Ball describes it, though the criticisms and misgivings weren’t so clearly religious as they had been, they centred on a suspicion about unrestrained curiosity and questioning, which might lead to an undermining of the social order (a big issue after the recent upheavals in England), and to atheism (they were on the money with that one). They had a big impact on the Royal Society, which struggled to survive in the late seventeenth and early eighteenth centuries. It’s worth noting too, that the later eighteenth century Enlightenment on the continent was much more political and social than scientific.

But rather than try to analyse these criticisms, I’ll provide a rich sample of them, without comment. None of them are ‘representative’, but together they give a flavour of the times, or of the more conservative feeling of the time.

[Is there] anything more Absurd and Impertinent than a Man who has so great a concern upon his Hands as the Preparing for Eternity, all busy and taken up with Quadrants, and Telescopes, Furnaces, Syphons and Air-pumps?

John Norris, Reflections on the conduct of human life, 1690

Through worlds unnumber’d though the God be known,

‘Tis ours to trace him only in our own….

The bliss of man (could pride that blessing find)

Is not to act or think beyond mankind;

No powers of body or of soul to share,

But what his nature and his state can bear.

Why has not a man a microscopic eye?

For this plain reason, man is not a fly.

Say what the use, were finer optics giv’n,

T’inspect a mite, not comprehend the heav’n? …

Then say not man’s imperfect, Heav’n in fault;

Say rather, man’s as perfect as he ought:

His knowledge measur’d to his state and place,

His time a moment, and a point his space.

Alexander Pope, An Essay on Man

There are some men whose heads are so oddly turned this way, that though they are utter strangers to the common occurrences of life, they are able to discover the sex of a cockle, or describe the generation of a mite, in all its circumstances. They are so little versed in the world, that they scarce know a horse from an ox; but at the same time will tell you, with a great deal of gravity, that a flea is a rhinoceros, and a snail an hermaphrodite.

… the mind of man… is capable of much higher contemplations [and] should not be altogether fixed upon such mean and disproportionate objects.

Joseph Addison, The Tatler, 1710

But could Experimental Philosophers find out more beneficial Arts then our Fore-fathers have done, either for the better increase of Vegetables and brute Animals to nourish our bodies, or better and commodious contrivances in the Art of Architecture to build us houses… it would not onely be worth their labour, but of as much praise as could be given to them: But as Boys that play with watry Bubbles, or fling Dust into each others Eyes, or make a Hobby-horse of Snow, are worthy of reproof rather then praise, for wasting their time with useless sports; so those that addict themselves to unprofitable Arts, spend more time then they reap benefit thereby… they will never be able to spin Silk, Thred, or Wool, &c. from loose Atomes; neither will Weavers weave a Web of Light from the Sun’s Rays, nor an Architect build an House of the bubbles of Water and Air…  and if a Painter should draw a Lowse as big as a Crab, and of that shape as the Microscope presents, can any body imagine that a Beggar would believe it to be true? but if he did, what advantage would it be to the Beggar? for it doth neither instruct him how to avoid breeding them, or how to catch them, or to hinder them from biting.

[Inventors of telescopes etc] have done the world more injury than benefit; for this art has intoxicated so many men’s brains, and wholly employed their thoughts and bodily actions about phenomena, or the exterior figures of objects, as all better arts and studies are laid aside.

Margaret Cavendish, Observations upon Experimental Philosophy, 1666

[A virtuoso is one who] has abandoned the society of men for that of Insects, Worms, Grubbs, Maggots, Flies, Moths, Locusts, Beetles, Spiders, Grasshoppers, Snails, Lizards and Tortoises….

To what purpose is it, that these Gentlemen ransack all Parts both of Earth and Sea to procure these Triffles?… I know that the desire of knowledge, and the discovery of things yet unknown is the pretence; but what Knowledge is it? What Discoveries do we owe to their Labours? It is only the discovery of some few unheeded Varieties of Plants, Shells, or Insects, unheeded only because useless; and the knowledge, they boast so much of, is no more than a Register of their Names and Marks of Distinction only.

Mary Astell, The character of a virtuoso, 1696

There are many other such comments, very various, some attempting to be witty, others indignant or contemptuous, and some quite astute – the Royal Society did have more than its share of dabblers and dilettantes, and was far from being simply ‘open to talents’ – but for the most parts the criticisms haven’t dated well. You won’t see The Virtuoso in your local playhouse in the near future. Wide-ranging curiosity, mixed with a big dose of scepticism and critical analysis of what the contemporary knowledge provides, has proved itself many times over in the development of scientific theory and an ever-expanding world view, taking us very far from the supposedly ‘better arts and studies’ the seventeenth century pundits thought we should be occupied by, but also making us realize that the science that has flowed from curiosity has mightily informed those ‘better arts and studies’, which can be perhaps best summarized by the four Kantian questions, Who are we? What do we know? What should we do? and What can we hope for?

a particle of curiosity

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Curiosity, switched on, can take you to a fabulous place very quickly. Look at this piece of paper. What is it made of? What does it look like? If you were a nanoparticle – but what kind of nanoparticle? – landing on this paper, would you, in fact, land? Would you pass through it? And how long would that take you? And what would it feel like? What colours would you see? What patterns would you make? What dangers would you encounter? Would you be able to demarcate boundaries? Should you revel in the experience or take copious notes? It would be magical, but do you believe in magic? Perhaps only if your nanoparticle life is a matter of a moment….

Written by stewart henderson

May 30, 2013 at 7:47 pm