Thony Christie on Hevelius

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If you have any interest in the his­tory of astro­nomy you should be fol­low­ing The Renais­sance Math­em­aticus blog and this post, The last great naked eye astro­nomer, is a per­fect example of why. This is a post about Johannes Hev­elius who has to be one of the most fam­ous unheard of astro­nomers ever.

That doesn’t make sense I know. There are a lot of people who haven’t heard of Hev­elius, but if you have heard of Hev­elius, then the idea that people haven’t heard of him seems non­sense because his work is every­where in astronomy.

Scutum constellation in the Uranographia

Scu­tum in the Urano­graphia by Hev­elius. Source: Wikipedia.

Everyone’s happy that most con­stel­la­tions are ancient, but what is less well-known is that not every star was in a con­stel­la­tion. There were gaps between con­stel­la­tions filled with faint and bor­ing stars. These were called αμορφοι amorphoi or unformed stars by the Greeks. This is no good if you want to do sci­ence, because things like comets don’t stick to the inter­est­ing parts of the sky. That’s why map­ping was so import­ant in the Renais­sance. In the case of Hev­elius, his maps were so use­ful that he formed seven con­stel­la­tions that stay with us to this day.

I’ll admit con­stel­la­tions like Lacerta or Vulpec­ula aren’t fam­ous con­stel­la­tions, but he was work­ing with the haps between con­stel­la­tions. The fact that his charts were made of con­stel­la­tions vis­ible in Europe shows he was work­ing in a highly com­pet­it­ive space.

It’s easy to take this kind of work for gran­ted. The out­put can be seen as an uncon­tested fact, but Thony’s post put’s Hevelius’s work into the con­text of its time includ­ing the often intense sci­entific rivalry between astro­nomer defend­ing per­sonal and national status.

The also shows that while with hind­sight it seems obvi­ous that tele­scopes would bring more accur­ate meas­ure­ments, at any given time in his­tory it’s not always obvi­ous that new tech­no­logy is The Next Big Thing, it could be a dis­trac­tion or Expens­ive Dead End.

Would Copernicus have been more convincing if he’d been more accurate?

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As a follow-up to yesterday’s post, I was won­der­ing if Coper­ni­cus would have been more con­vin­cing if he’d used ellipses in his model instead of circles. By using circles Coper­ni­cus had to use epi­cycles like Ptolemy, though not so many. Still, it gave the impres­sion that epi­cycles were neces­sary. If that’s the case then why not have a sta­tion­ary Earth as well? The dis­cov­ery that plan­et­ary motion would be bet­ter described by ellipses didn’t come about till Kepler’s work almost a cen­tury later. As far as the post title goes, I think Dr* T’s The­ory #1 applies here: Any tabloid head­ing that starts ‘Is this.…’, ‘Could this be…’ etc. can be safely answered ‘No’

So my post title is a bit of a cliché, but the reason I’ve used it is that if the answer is no, then some­thing strange is hap­pen­ing. More accur­ate is less convincing?

The reason I think that is that Coper­ni­cus’ model wasn’t isol­ated from the rest of thought for that period. It used and built on a num­ber of assump­tions of the time. One of those ideas was the cre­ation of the uni­verse by a per­fect being. Another was the idea that a circle was a per­fect shape, derived from clas­sical geo­metry. By telling people the Sun was at the centre of the uni­verse and not the Earth, Coper­ni­cus was ask­ing people to make a big shift in their think­ing. A lot of people thought it non­sense. If he’d made the orbits ellipt­ical as well then many people who would have been will­ing to listen to Coper­ni­cus’ ideas would have balked at that, redu­cing his poten­tial audi­ence fur­ther. In terms of num­bers, the pop­u­la­tion of math­em­at­ic­ally minded people who could exam­ine his work was small enough already.

If he’d reduced the num­ber of ini­tial read­ers fur­ther, would his ideas have spread enough for oth­ers to pick them 50 years later? It’s impossible to say, but if Coper­ni­cus hadn’t given Kepler the idea of a put­ting the Sun at the centre of uni­verse, could Kepler have dis­covered it inde­pend­ently? It’s hard to say but, given how Kepler struggled with let­ting go of circles and using ellipses, I think it’s unlikely.

This is why I’m wary of his­tor­ies of sci­ence that are purely about who got it right and who got it wrong. Coper­ni­cus’ use of circles isn’t ‘right’, but it was neces­sary at the time.

I’ve «cough» bor­rowed the por­trait of Coper­ni­cus from Prof Reike’s page on Coper­ni­cus. It’s well worth vis­it­ing if you want to find out more about the astronomer.

You can read more about Kepler’s dis­cov­ery of the ellipt­ical path of plan­ets at:
Boc­caletti 2001. From the epi­cycles of the Greeks to Keplerʼs ellipse — The break­down of the circle paradigm

Copernicus and the Star that was bigger than the Universe

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I’ve been try­ing to watch Cos­mos by Carl Sagan. I’ve never seen it and it’s prov­ing to be a bit of a struggle. He def­in­itely can write. Some of the sequences are fant­astic, but some of it is badly dated. The thing that really grates to me is his dis­missal of Ptolemy and his geo­centric uni­verse. For Sagan at best Ptolemy’s sys­tem held back astro­nomy by 1,500 years. At worst he’s only worth men­tion­ing to say he’s dead wrong, like in the first episode.

It’s not really fair to lay into Sagan for his atti­tude to Ptolemy. His work is a product of its time and it was writ­ten over thirty years ago. But the idea that Ptolemy was clearly wrong seems to the pop­u­lar under­stand­ing of Renais­sance astro­nomy. The ques­tion here is Why did some people oppose the helio­centric the­ory of the uni­verse? not Who in their right mind would accept it? It over­looks the power of the Ptole­maic sys­tem. If you fol­lowed Ptolemy’s work you could pre­dict where the plan­ets would be with enough accur­acy for naked-eye astro­nomy. If Coper­ni­cus had only used simple circles, then his model might have seemed bet­ter, but he too needed to add epi­cycles and fudges to make his sys­tem match the observ­able sky. It needed fewer epi­cycles, but it was hardly perfect.

Pop­u­lar belief is that the prob­lem was solved when Galileo picked up his tele­scope and proved the helio­centric the­ory. In fact a recently pub­lished paper by Chris­topher Graney, The Tele­scope Against Coper­ni­cus: Star Obser­va­tions by Ric­ci­oli Sup­port­ing a Geo­centric Uni­verse in the Journal for the His­tory of Astro­nomy shows that the tele­scope could have dealt a ser­i­ous blow to the Coper­nican model of the uni­verse.
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Planets and Anomalies in the Antikythera Mechanism

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This post was chosen as an Editor's Selection for ResearchBlogging.orgMath­em­aticians have a concept, Omega, that is defined as some­thing so huge that any attempt to define it actu­ally defines some­thing smal­ler. In a sim­ilar vein I reckon that any attempt to describe the ingenu­ity of the Anti­kythera Mech­an­ism actu­ally ends up describ­ing some­thing less ingeni­ous instead. More research on the device has been pub­lished recently in the Journal for the His­tory of Astro­nomy. I real­ise that people might be drop­ping on to this entry from a search engine, without hav­ing read any of the earlier posts, here’s a quick recap of what the mech­an­ism is.
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Astronomy in Metal Heaven

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Astro­labes at the Museum for the His­tory of Sci­ence at Oxford.

If you ever want to embar­rass me, try to get me to enthuse about a dis­play of astro­labes. They’re the kind of thing I should love. They’re devices for show­ing what is vis­ible in the sky at any given time. They’re very sim­ilar to the plan­i­spheres that people use today. The math­em­at­ics behind them is eleg­ant. The best also tend to have extraordin­ar­ily ornate metal­work to com­ple­ment the soph­ist­ic­a­tion of the devices. Yet, when they’re hanging up like this, they leave me cold.

I think the reason is that an astro­labe on dis­play is a dead astro­labe. There are bet­ter ways to show a static night sky. What you need is an astro­labe in motion to appre­ci­ate them. That’s what makes this talk by Tom Wujec so good. He demon­strates how you could use an astro­labe to tell the time. In his hands, an astro­labe becomes a lot more interesting.

Tom Wujec demos the 13th-century astro­labe video from TED.

It’s easy to under­es­tim­ate how much you can do if you’re will­ing to observe intently. What I also like about this talk is that Tom Wujec emphas­ises the import­ance of con­nect­ing with the night sky. You could claim accur­ate clocks have broken this con­nec­tion, but I’m not sure that’s the case. Where I live light pol­lu­tion is often so bad that I could not use an astro­labe. He’s right to point out that you can lose things with pro­gress. Iron­ic­ally Global Astro­nomy Month with try to show how immense the uni­verse is, while arte­facts like this show that on a day-to-day basis for urban dwell­ers the vis­ible world is much smal­ler than the cos­mos of the past.

You can see many astro­labes like the one below at the Museum of the His­tory of Sci­ence, Oxford.

A Persian Astrolabe at the Museum for the History of Science at Oxford.

A Per­sian Astro­labe at the Museum for the His­tory of Sci­ence at Oxford.

Mysteries and Discoveries of Archaeoastronomy by Giulio Magli

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Note: Giulio Magli was one of the exam­iners of my thesis, so his book is hardly likely to get a bad review.

This review rounds off a tri­logy to go with Sky­watch­ers, Sham­ans and Kings and People and the Sky. Like the other two books this could be said to be part of a World Archae­oastro­nomy approach, but Giulio Magli adds a twist. Some of this is down to the approach he’s taken to archae­oastro­nom­ical sites, but he also adds a bit more.

Magli’s approach is sim­ilar to what I would have done if I was writ­ing an intro­duc­tion to archae­oastro­nomy book. He tackles the sites around the world. So take a deep breath because in his open­ing sec­tion of twelve chapters — slightly over half the book — he cov­ers. Palaeo­lithic Europe, Pre­his­toric Bri­tain, the temples of Malta, Egypt, Babylon, East North Amer­ica with the Hopewell and Cahokia, West North Amer­ica with Chaco and the Ana­sazi, North­ern Mex­ico and Tenoch­tit­lan, The rest of Mesoamer­ica and Palenque, The Incas, Nazca and Poly­ne­sia. That leaves massive holes where you would expect to find India, China, Korea and Japan and a lack of African mater­ial. That’s more due to the state of play in aca­demic archae­oastro­nomy at the moment than a fault of Magli. In gen­eral Africa has been greatly over­looked and there’s not a lot of integ­ra­tion between Asian astro­nomy and the rest of the world. It’s get­ting bet­ter, but it’s still under-represented com­pared to the May­ans and Pre­his­toric Europe.

If this had been the sum total of the book I wouldn’t be that enthu­si­astic about it. It’s not bad. It’s writ­ten from an astro­nom­ical point of view with some amus­ing digs against archae­olo­gists. If you were inter­ested in archae­oastro­nomy and approach­ing it from astro­nomy and not anthro­po­logy I’d recom­mend this over Aveni or Krupp’s book as an intro­duc­tion to the field. What really marks out the book as worth read­ing is sec­tion 2.
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Are Extraterrestrials a Greek thing?

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I had a slight worry earlier today. I have an idea that I think has cross-over rel­ev­ance between SETI and Ancient His­tory about ancient spec­u­la­tions on extra­ter­restrial life. I was slightly alarmed when I read Jean Schneider’s new pre-print on arXiv, The Extra­ter­restrial Life debate in dif­fer­ent cul­tures. In it Schneider argues that argu­ments about life on other worlds can be traced back to ancient Greece. It sounds like an idea I’ve been kick­ing around for a couple of months. It was a topic raised by the atom­ists like Demo­critus and Leu­cip­pus who said that in an infin­ite cos­mos with an infin­ite num­ber of atoms there must be infin­ite worlds. Plato rejec­ted this idea, as did Aris­totle who argued for a hier­arch­ical cos­mos. Schneider says debates in other cul­tures are derived from this and then asks why it should be only the Greeks who spec­u­lated on off­world life.
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Re-thinking the archaeology of Mars

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I’ve been rum­ma­ging through the depths of my hard-drive and found a few things I’d for­got­ten about. Here’s one of them, from 2006 I see, a present­a­tion on the con­tem­por­ary archae­ology of Mars.

The reason I’ve pulled it up is I might want to go back and think this over again. I’m not happy with it, which is why it was left on the drive, but it might have potential.

The slide on the 1980s probes is inten­tion­ally blank, because there were hardly any probes sent in the 1980s to Mars. The reason is that the com­pet­i­tion between the major powers has moved to Earth Orbit, with the USA build­ing the Shuttle and the USSR build­ing long-term space sta­tions. Recent events have high­lighted a couple of reas­ons why it’s worth look­ing at this again. One is the regis­tra­tion of lunar her­it­age by Cali­for­nia, which is grabbing head­lines for some­thing that Alice Gor­man and Beth O’Leary have been say­ing for a while. The other is Obama’s can­cel­la­tion of the return to the Moon.

It could be a sci­entific re-prioritisation, but like the Mars gap in the 1980s, it could also be due to polit­ics. The Nobel laur­eate already has wars in Iraq and Afgh­anistan to man­age, and he wants to keep his options open for a war with Iran. That could turn very nasty as Iran is next door to his two other prob­lems. It’s pos­sible that there simply isn’t a threat on the Moon, but there is in the Middle East. Unless China devel­ops lunar ambi­tions, the dis­cov­ery of water on the Moon could be a sci­entific curi­os­ity rather than a step­ping stone to colonisation.

There’s a few reas­ons why I don’t like this present­a­tion as it stands. I think the biggest prob­lem is that one of the big factors for mak­ing it was that I needed a present­a­tion. It wasn’t an idea that was ready, and to some extent the prob­lem was “there’s some­thing archae­ology could say about this, but what?” Now I’m think­ing about the social, polit­ical and eco­nomic effects of Mars explor­a­tion. This time around I see archae­ology as a tool to find­ing out about these factors, rather than ‘being archae­olo­gical’ as the pur­pose of project.

It’s not just Jack who names the planets

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Gliese 667c. Connected to, but definitely not, Ganymede in Lyra's naming system. Photo (c) Nasa.

An artist’s impres­sion of Gliese 667c. Con­nec­ted to, but def­in­itely not, Ganymede in Lyra’s nam­ing sys­tem. Photo © Nasa.

Wladi­mir Lyra’s fol­low­ing in the foot­steps of Jack in his arXiv paper Nam­ing the extra­solar plan­ets. Cur­rently plan­ets are tagged after their par­ent star, so if we found a planet around α Ceti, it would be called α Ceti b. The b in lower case is used for the first planet to be found, c for the second and so on. a is not used to avoid con­fus­ing a planet with a star. Unfor­tu­nately in the case of some double stars a cap­ital B would be used for the second star, so names could get con­fus­ing. So why not name the plan­ets? Lyra gives a couple of reas­ons why he thinks this would be a good idea. One is that names like Bac­chus are more beau­ti­ful than names like HD 128311. One person’s beauty is another person’s mess, so I’m not con­vinced by this. How­ever, he also pro­poses that names for extra­solar plan­ets aren’t just dec­or­at­ive, there’s also the Coper­nican prin­ciple.

“Mer­cury — Venus — Earth — Mars is a sequence of equals. Sol b — Sol c — Earth — Sol d would impli­citly imply that the Earth is spe­cial in some way.” For this reason, Lyra argues that nam­ing the extra­solar plan­ets is neces­sary to avoid the impres­sion that the Solar sys­tem is spe­cial. I’m more per­suaded by this, but it misses an obvi­ous point — the Solar sys­tem is spe­cial. It’s where I am, it’s where all humans are and it’s where they’ll be for the fore­see­able future.

My biggest objec­tion to his paper was that I’m not sure how help­ful it would be. Even deal­ing with ancient his­tor­i­ans I tend to avoid clas­sical names for stars, except in a few cases. Vin­demi­at­rix or Protry­getor, names for the same star in Latin or Greek aren’t as help­ful as ε Vir­ginis, because ε Vir­ginis gives the reader a clue as to where in the sky they’ll find the star. Sim­il­arly I can see why Lyra would give the name Bellero­phon to a planet, but I wouldn’t find it as help­ful as 51 Pegasi b. The IAU have said there are likely to be too many extra-solar plan­ets to name. The prob­lem isn’t likely to be the sup­ply of names, which is a shame as Lyra solves that neatly. It’s mem­or­ising what goes where.

For that reason I’d prefer a Bayer style sys­tem so in the ε Erid­ani sys­tem you could num­ber the plan­ets from inner­most orbit to outer I, II, III and so on. It sounds simple, but it won’t work. The first star you find in a sys­tem is likely to be the most massive, not the closest to the star. Using this sys­tem you wouldn’t be able to num­ber plan­ets until you dis­covered every planet in the sys­tem. Every time you dis­covered a new planet you’d have to renum­ber the sys­tem, caus­ing havoc when you try and use older papers for com­par­ison which use a dif­fer­ent num­ber­ing, or else have a data­base of each system’s num­ber order for plan­ets. Another solu­tion would be to num­ber plan­ets in order of mass, but that’s not likely to be fool-proof either.

Another pos­sib­il­ity would be a Bayer style des­ig­na­tion which embed­ded inform­a­tion about a planet in its name. So Gliese 876 d would be Gliese 876 p1.9379, p for planet and the num­ber fol­low­ing it is the orbital period. This too has flaws though as orbital peri­ods can be cal­cu­lated from assumed masses and may be revised in the future. A pos­sible solu­tion would be to only give names to the min­imum num­ber of sig­ni­fic­ant fig­ures neces­sary. In the Gliese 876 sys­tem that would give plan­ets names p60 for b, p30 for c and p2 for d. The exact fig­ures may change, but the rel­at­ive order of peri­ods would mean you would have a fair chance of identi­fy­ing a planet named in a early paper on the sys­tem at some time in the future.

Things do change and cata­strophes occur upset­ting sys­tems. Hybrid names like 55 Can­cri p 5000 Argive might help track ref­er­ences to 55 Can­cri d as papers accrue over the years. I’ll cheer­fully con­cede a name like Althaea for planet 16 Cygni Bb (the first star dis­covered orbit­ing 16 Cygni B, hence the Bb) would be easier to under­stand. Ulti­mately though I think the prob­lem is not the names, or their alloc­a­tion. It’s what the names are used for.

The vis­ible plan­ets had names because they were vis­ible, dis­tinct­ive and needed names. Uranus and Nep­tune also got names because there were so few plan­ets so more names were not men­tally tax­ing. Lyra points out that aster­oids have names. This is true, but when 1 Ceres and 2 Pal­las were dis­covered it wasn’t anti­cip­ated that 2309 Mr Spock would be join­ing them. These days a cata­logue num­ber is essen­tial to identify an aster­oid, the name is not so import­ant. The same can be said of comets. Ori­gin­ally they were named by the date they appeared. After the dis­cov­ery of the peri­od­icity of comets by Hal­ley, they began to be named, but these days comets also bear cata­logue num­bers. So who will use these planet names?

Ontic dump:

A name for some­thing that car­ries inform­a­tion about it. e.g. An example Stew­art and Cohen give is if you know what an arrow and a head are, you can work out what an arrow­head is, even if you haven’t come across that word before.

For the vast major­ity of the extra­solar plan­ets their exist­ence will only be noted by astro­nomers, much like stars and galax­ies today. While names may be beau­ti­ful, astro­nomers don’t seem to use them for stars, nore for many galax­ies. Like­wise names may add some­thing of value to extra­solar plan­ets, but equally use of them on a reg­u­lar basis could be cum­ber­some. Names have most value where things are not eas­ily cat­egor­ised, like the rocks on Mars. Myth­o­lo­gical names have the fur­ther dis­ad­vant­age in that they are purely abstract rather than ontic dumps. An ontic dump would have the double use of not only labelling a planet, but giv­ing some inform­a­tion about it. Bayer clas­si­fic­a­tions, when used as names, are usu­ally ontic dumps, as are the cur­rent extra­solar planet names. This mat­ters in the Lyra name sys­tem as some of the names actu­ally run counter to Graeco-Roman cosmology.

As an example the name Dike is asso­ci­ated with a planet found in Libra. In clas­sical myth­o­logy Dike, Justice, is in fact an aspect of Virgo. Libra was ori­gin­ally the Claws of Scor­pio. Once the method is explained then the Lyra sys­tem makes sense, but it would be counter-intuitive in some cases for any­one with a know­ledge of clas­sical myth­o­logy. Another example would be that Amphitrite, the nymph wooed by Pos­eidon with the aid of Del­phinus is not asso­ci­ated with con­stel­la­tion Del­phinus. If names are to be used then a method divorced from the myth­o­lo­gic­ally laden mean­ings of the mod­ern con­stel­la­tions might pre­vent con­fu­sion. That’s why I think Stuart’s sug­ges­tion to use names from all sorts of lit­er­at­ure has a lot of merit. Though there’s some­thing to be said for Exoplanetology’s sug­ges­tion too.

Ulti­mately the names for the extra­solar plan­ets will be names that have mean­ing to the com­munity of reg­u­lar users. In the past clas­sical ref­er­ences were com­mon cul­ture shared by aca­dem­ics in all European uni­ver­sit­ies. Those days have gone. I could bemoan the decline in clas­sics, after all I’m an ancient his­tor­ian. But there’s also a lot to cel­eb­rate about the cre­ation of aca­demic links out­side the Euro-American com­munity. If names are adop­ted hope­fully they’ll reflect that it’s not just the num­ber of worlds that has grown, but also the astro­nom­ical com­munity from a small élite at the start of the 20th cen­tury to the world­wide exchange of inform­a­tion and ideas that we have today.

If you’re won­der­ing who Jack is, there a video on You­Tube.

The Antikythera Mechanism: Art or Science?

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The Antikythera Mechanism. Photo (cc) Tilemahos Efthimiadis.

The Anti­kythera Mech­an­ism. Photo (cc) Tilema­hos Efthimi­adis.

This post was chosen as an Editor's Selection for ResearchBlogging.orgSome posts take quite a while to write. This is a response to Candy Minx and Mar­tin Rundk­v­ist who were dis­cuss­ing the Anti­kythera Mech­an­ism back in 2006 (Anti­kythera, Time, A Reply to the Minx). Candy Minx thought that the Anti­kythera Mech­an­ism was an expres­sion of what was already known and embed­ded in a soci­ety through things like myth and ritual. Mar­tin thought that the mech­an­ism was far more com­plex, indeed need­lessly com­plex, for an ancient soci­ety and so was some­thing quite dif­fer­ent to the folk astro­nomy of the time. Ori­gin­ally I planned to write a fence-sitting com­prom­ise. I thought that Candy Minx was right to an extent, there was no need for a device like this because rituals and folk obser­va­tion could allow people to time the year as well as they needed. At the same time I thought that Mar­tin was right to point out that the mech­an­ism gave res­ults with far more accur­acy than folk astro­nomy needed, or would even recog­nise. A dif­fer­ent sort of astro­nomy is vis­ible in the Anti­kythera Mech­an­ism. I didn’t blog too much about the 2006 paper because I atten­ded a few of Mike Edmunds’ talks on the topic and heard that more would be pub­lished, which happened in 2008. Any­how in my own fluffy and fence-sitting way I’ll now offer my compromise.

Someone with an extraordin­ary ima­gin­a­tion built the Anti­kythera Mech­an­ism and, if he were alive today, we wouldn’t hes­it­ate to call him a sci­ent­ist. I don’t know if the designer was in the same league as New­ton or Galileo, but he was cer­tainly the equal of Kepler, Coper­ni­cus or Brahe. It’s hard to over­state how extraordin­ary the device described in the 2006 paper is, but I’m going to give it a go.

If you’re the one per­son who hasn’t heard of the Anti­kythera Mech­an­ism then Nature have a handy video introduction.

All that remains now is a col­lec­tion of cor­roded lumps found off the island of Anti­kythera. The 2006 paper described what the team dis­covered after x-raying the lumps to read the hid­den inscrip­tions without priz­ing apart the device and dam­aging it. Prior to this paper it was thought that the device could keep track of the Sun and the Moon. This is no small feat.

Epicycle et deferent. Image by Dhenry @ Wikimedia Commons.
Epi­cycle et defer­ent. Image by

The Sun would be mov­ing slowly against the back­ground stars, so over the course of a year it would pass through all the signs of the zodiac. The Moon how­ever is more com­plex. The Moon also moves in front of the back­ground stars, but it only takes about 27 days to do this. It’s called the sider­eal period. So you need a couple of gears to drive those two motions. But you wouldn’t really think of the sider­eal period as a month. For most people the syn­odic period, the time between one New Moon and the next or the time between one Full Moon and the next, is a month. This is around 29½ days. Throw in extra gears for driv­ing other dis­plays show­ing eclipse cycles and it’s clearly a com­plex device. The ori­ginal stud­ies found evid­ence of epi­cycles, gears moun­ted on other gears. Add other fea­tures like dis­plays for eclipse and lunar cycles on the back and it’s obvi­ous you have a com­plic­ated device. The 2006 research showed that in fact it was all a bit more com­plic­ated than that.

The Moon’s move­ment isn’t con­stant. It speeds up and slows down. This is because its orbit isn’t exactly cir­cu­lar. Instead it’s slightly egg-shaped. The point fur­thest from the earth is the apo­gee and the point closest to the Earth is the peri­gee. When it’s near the apo­gee it travels slowly, but when it moves closer to the Earth it picks up speed until it passes peri­gee and then it slows down again. This is called the first lunar anom­aly. The dif­fer­ence is notice­able by the naked eye, if you’re will­ing to make sys­tem­atic obser­va­tions. This is all simply explained by Kepler’s Laws of Plan­et­ary Motion. There’s small prob­lem. Kepler used ellipses.

You can’t use ellipt­ical gears. The point of gears is that they must have inter­mesh­ing teeth. An ellipt­ical gear would lose con­tact with the driv­ing gear as its axis changed. Instead it seems that the mech­an­ism used two gears, one slightly off-axis from the other. The rota­tion was con­nec­ted by a pin-and-slot arrange­ment, so that the one gear wouldn’t turn at quite the same rate as the other gear. The on-axis gear can then be turned reli­ably by the drive gears, while the motion of the moon can driven by the off-axis gear. So you have a device that can track the sider­eal, syn­odic and anom­al­istic months, all while the Earth is spin­ning round the Sun. If that’s caus­ing your head to spin you might want to skip the next paragraph.

There’s another prob­lem. The lunar anom­aly describes the Moon’s travel from one apo­gee to the next. This apo­gee is also rotat­ing around the earth. If the apo­gee is in Aries then two and a bit years later it will be in Can­cer, and another two and a bit years to move into Libra until it too has trav­elled through the zodiac over about nine years. So now we have a device which tracks the Moon around the Earth, and its phases and it’s vari­able speed and vari­ations in that vari­ab­il­ity, while also keep­ing track of the Sun’s pos­i­tion, poten­tial lunar and solar eclipses and inter­cal­a­tion cycles so you know when to stick an extra month in to keep the lunar months in step with the solar year round gears, some moun­ted slightly off axis to cre­ate a pseudo-sinusoidal vari­ation using cir­cu­lar gears to replace ellipses. If you have funny feel­ing near the back of your head right now, that’s prob­ably your brain try­ing to crawl out of your ears. The Anti­kythera Mech­an­ism is insanely com­plex. Still just because it’s insanely com­plex, that doesn’t make it sci­entific.

In fact you can argue about whether or not Sci­ence exis­ted in the ancient world. Cer­tainly a lot of ele­ments like test­ing ideas with exper­i­ments didn’t really become pop­u­lar till after Galileo. On the other hand some nat­ural philo­sophy of the time was based on obser­va­tion. There was cer­tainly tech­no­logy which was the res­ult of applied know­ledge. With those kind of pro­visos a lot of ancient his­tor­i­ans would be happy with the idea of ancient sci­ence, albeit a sci­ence dif­fer­ent to post-Renaissance sci­ence. In this case, the sheer intense obser­va­tion and cal­cu­la­tion involved in mak­ing the Anti­kythera Mech­an­ism marks it out as a work of ancient sci­ence. There’s also another factor which might make it more sci­entific than artistic.

To some extent the Anti­kythera Mech­an­ism Research Pro­ject have been inter­ested in hanging a name on the device. It was thought to have ori­gin­ated in Rhodes and sunk on its way to Rome, which would have con­nec­ted it to the home city of Hip­par­chus, one of the great astro­nomers of antiquity. The 2008 paper has examined the parapegma on the mech­an­ism and dis­covered it may be con­nec­ted to Syra­cuse, home of Archimedes.

A parapegma is a cal­en­dar, usu­ally with holes for stick­ing a peg into for mark­ing the days. In the case of ancient Greece they’re inter­est­ing when they tell you what day of the month it is, because each Greek city had its own set of months. The months were usu­ally named after reli­gious fest­ivals, and this was tied into local polit­ics. That meant hav­ing your own cal­en­dar was a good way of show­ing your inde­pend­ence. The best match for the months men­tioned on the mech­an­ism is Taur­omenion, mod­ern Taorm­ina, in Sicily. This is likely to have shared some months with Syra­cuse as it was re-settled from there in the fourth-century BC, so Syra­cuse is a strong pos­sib­il­ity for the home of this device. Archimedes is said to have inven­ted a plan­et­arium accord­ing to Cicero and is thought to have writ­ten a lost book on astro­nom­ical devices. How­ever he could not have made this device. Archimedes died in 212 BC. The Anti­kythera Mech­an­ism is cur­rently thought to date to the second half of the second cen­tury BC, but that might change. But it was very likely to have been made after Archimedes death and that’s what makes it scientific.

Art can be col­lab­or­at­ive, or it can be per­sonal. Sci­ence in con­trast is built on cumu­lat­ive know­ledge. The per­son who inven­ted the gear­ing did not have to be the per­son who made the astro­nom­ical obser­va­tions. He didn’t even need to live in the same cen­tury as the astro­nomer. In fact the maker of this device might not have done either. He could have fol­lowed a kit and added his own per­sonal touches on the cas­ing. There’s a core to this device which, once expressed, is inde­pend­ent of per­sonal vis­ion. Archimedes didn’t have his own per­sonal Moon which moved in a dif­fer­ent way to every­one else’s, while an artist can have a per­sonal inter­pret­a­tion of the Moon.

A reason people might think the Anti­kythera Mech­an­ism is a work of art is that it’s clearly the res­ult of a lot of ima­gin­a­tion. Great art requires ima­gin­a­tion, but so too does great sci­ence. It requires the kind of ima­gin­a­tion that can look at a tool­box full of circles and see ellipses. The kind of ima­gin­a­tion that can watch wheels turn within wheels as bod­ies waltz to the music of the celes­tial spheres. Another com­mon factor between art and sci­ence is that great art can show a new way of look­ing at the world, and great sci­ence does this too. That’s why I dis­agree with Candy Minx when she says “Sci­ence is always play­ing catch up with the poets.” Sci­ence can reveal beauty too, as a visit to the Anti­kythera Mech­an­ism Research Group’s homepage would show.

Freeth, T., Bit­sa­kis, Y., Mous­sas, X., Seirada­kis, J., Tse­li­kas, A., Mangou, H., Zafeir­o­poulou, M., Had­land, R., Bate, D., Ram­sey, A., Allen, M., Craw­ley, A., Hockley, P., Malzbender, T., Gelb, D., Ambrisco, W., & Edmunds, M. (2006). Decod­ing the ancient Greek astro­nom­ical cal­cu­lator known as the Anti­kythera Mech­an­ism Nature, 444 (7119), 587–591 DOI: 10.1038/nature05357

Freeth, T., Jones, A., Steele, J., & Bit­sa­kis, Y. (2008). Cal­en­dars with Olympiad dis­play and eclipse pre­dic­tion on the Anti­kythera Mech­an­ism Nature, 454 (7204), 614–617 DOI: 10.1038/nature07130

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