Cosmic Navigation and Cosmic Pilots

As we embark on a new academic year with our Arabic reading group, we start more in earnest to tackle the pages of Sulayman al-Mahri’s Mir’at al-salak li-kurat al-aflak (Mirror of Travellers into the Heavenly Spheres), a primer of astronomy for the education of maritime pilots in the early 15th century. Not so much of a primer really, but more like an intermediate-level handbook of cosmography.

The first pages tell us about the order of the heavenly orbs, how the universe is conceived as… an onion (that’s my image, not al-Mahri’s!), or more elegantly, as a compound of concentric spheres, within each of which move the planets or other heavenly bodies. It all starts from the centre of the earth, with the description of the elemental spheres wrapped around it: water, air, fire. This cosmology is of course in all its basics an Aristotelian cosmology, found in numerous accounts over most of ancient and medieval Eurasia. Latin versions abound, including some beautifully illustrated.

Gautier de Metz, 13th century.

Approximately at the same time that al-Mahri was writing his works, Iberian nautical science was being revolutionised by the incorporation of astronomical precision techniques to the extensive tried and tested savoir-faire of the pilots. Long-distance oceanic navigation elicited, or rather forced, technoscientific developments which brought its practitioners to new levels of skill. And yet, East or West, either in Atlantic or Indian Ocean waters, there is the lingering question: Did they really need to know about the system of the cosmos in order to take a ship from A to B? And if they did not need to know those cosmic subtleties, why did they keep learning them? Why would such a practical pilot as al-Mahri, who wrote excruciatingly detailed route descriptions, care to elaborate so much on what was practically philosophical knowledge? Was it just didactic inertia, a superstitious repetition of old doctrines?

The answer is most likely “No, they did not need to know,” just as a mechanic fixing a carburetor does not need to know the laws of physics, or a butcher the details of embryology. A more interesting question may be asked, though, especially in our times, when all the cosmology and astronomy of the nautical sciences has been encapsulated in little devices which use satellite geo-positioning technology, like GPS. The question, and we are only left to ponder, is How did that knowledge impact their navigation? Did it have any practical influence, or was it just a matter of “depth”, of ”taste” (sapere, saber, dhawq) added to the mental framework of the pilots? Next time you meet a 15th-century pilot, we know what to ask him! [JA]

A Planet-Less Nautical Astronomy

From the RUTTER crew conversations logbook, preserved for posterity: We have been wondering at the early modern pilots of the Indian Ocean, who famously used complex combinations of stars to navigate by night—a catalogue of about 150 celestial bodies was in their treatises— but, and here’s the question, without ever even bothering to mention the planets. By this I mean the five known at the time, Mercury, Venus, Mars, Jupiter and Saturn. The same planets without which Ptolemy’s astronomy would have been reduced to nothing, and the same planets without which astrology would have been unimaginable.

The reason for this absence is obvious, and it is a nice etymological lesson. A planet, as is well known, means in the original Greek a “wanderer”, a “vagabond”. Now, if you are going to depend on guidance through the night and through the vast expanse of the ocean, you cannot rely on something changeable. You need fixed, unchanging points of reference, and this is exactly what was provided by the night sky, those wanderers excepted.

How bright they are, and unflickering! We have just been witnessing in Lisbon the approach and conjunction of Venus and Jupiter, every day, in the sunset sky, very impressive. And yet for all their steady light, they are not good for navigation: one day they are here, next day there, one day going straight, next day retrograding… They are strong, but fickle. The importance that they have in the astrological view of the cosmos is quite indicative of the variable state of the world: matters of the world and we are not ruled by stars, which would make us constant, but by those wandering bright lights.

Photo: Jorge Rodrigues da Silva

The lack of importance that the planets have in navigation is, in turn, quite indicative of the nature of this craft, and of how special is the state of being at sea and being in transit to a destination: there is peril, and there is the urgency to reach a place, and so all the variable concerns of the pilot are subordinate to accomplishing his task, as Ibn Mājid says, “going and returning with the passengers and the cargo safe.” [JA]

Knowledge Weaponized

Towards the end of chapter 6 of his Fawā’id, after going over the complexities of various kinds of routes and course-plotting options, Ibn Mājid explains:

I have made distinctions (farraqtu), because the different skills (‘ulūm, “sciences”) are like weapons: sometimes you need a bow and sometimes a sword, sometimes a spear and sometimes an ax or a dagger, and yet, for all this, you may never be dispensed of using a knife.

The explicit point seems to be that every skill, as a subdiscipline of knowledge, has its own irreplaceable and particular application, and that it is necessary to have a rounded preparation, because, as he puts it later, borrowing a saying from Imam ‘Ali: “man is the enemy of anything he is ignorant of,” or rather, given the context, “man is at war with everything he is ignorant of” (al-insān ‘aduww mā jahilahu). That is (and we must put it in the context of piloting a ship through the ocean and having to land safely thousands of miles away), everything we ignore is a hostile prompt to catastrophic failure. And the obvious way to be prepared, or armed, is to acquire the panoply of knowledge required by our respective field.

The bodhisattva Kuan Yin, armed against ignorance (Wellcome Collection).

The implicit point is in that initial “making distinctions”, associated to terms like farq, “distinction, discrimination, severance”, and furqān, an epithet of the Qur’an meaning “a criterion”. As it happens, this root-meaning of division and discernment is exactly the same of the English-Germanic skill, and also of Latin scientia. The suggestion that science and skill have a common origin in discernment/dissection should give us pause now, as it would be better developed in another post.

So now, instead, going back to the image of waging war against ignorance, we can see how the mighty ancient saying is so much better when applied in science than in politics: Divide et impera! or in Arabic, Farriq tasud!, discern and you shall rule. [JA]

The Spacetime of Early Modern Navigation

As we continue to read chapter 4 of the Fawā’id, about the nautical rhumbs, and as we go through detailed descriptions of time and distance measurements, we come across technical concepts which in their practicalities bring us, once again, to reflect on some of the principles of our modern technoscience.

The distance unit in early modern Arab navigation was the zām (pl. azwām). The technical concept is the taraffā or tirfa, called by early Portuguese explorers the “Rule of the Leagues” (regimento das leguas), the function between the distance travelled, the latitude progress, and the azimuth of the destination: e.g. if you travel straight up north, it takes you one hour to shift your position by one degree northwards, but if you travel towards the north-east, it will take you longer to advance that same degree northwards. A nice image of this concept is given by the triangle below, where A is the point of origin, and the latitude difference between A and B would be one degree. Simply put: the AB diagonal path takes longer to reach the same parallel.

Now, how to measure the advance without any points of reference on the flat surface of the ocean? The key point is: time is a function of movement. Something has to move for there to be a sign of time, because, as ordinary language teaches us: “time passes”, and we speak about “a space” or “an extension” of time, and we ask “how long?” as if we were speaking of a stretch of a road or a piece of string.

The solution: look up from the surface of the ocean and into the sky, where the positions and the continuous movement of the heavenly bodies show us directions and show us time. This relation between movement and time brings to mind Plato’s formulation: “time is the moving image of eternity” (Timaeus 37d). A sundial illustrates this too, being somehow “a moving shadow of eternity”. The passing stars were the necessary reference, and so, one of the definitions of zām reads, “the distance it takes to raise the Pole Star by one eighth of a finger if the ship sails due north”.

Sundial, courtyard of the Great Mosque of Kairouan.

Fundamental coexistence of space and time, and strikingly obvious continuity of their dimensions… What to make, in this light, of the complexities of the space-time formalism of contemporary physics, with their illustrious history and mathematical refinements? Is this yet another case of “nothing new under the sun”? The word itself, spacetime, goes perfectly well with the medieval perception of navigators—the consubstantiality of space and time was immediately obvious. Perhaps it is just a matter of continuing to deepen the dialogue, the centuries-old conversation between the depths of metaphysical speculation and the frontlines of physical enquiry. Time will tell. [JA]