On this page, observations of various kinds will appear that are related to big history teaching, as well as to big history
HOW DID EUROPEANS ACQUIRE THE FIRST ACCURATE NAUTICAL CHARTS AND ARABIC NUMERALS?
My in-class experiments with nautical navigation technology around the time of Columbus have not only yielded the results described
in earlier blogs, but they have also led to a reappraisal of the questions of how late-medieval Europeans succeeded in making the
remarkably accurate nautical charts of the Mediterranean Sea known as portolans
(harbor city maps), while also acquiring Arabic numerals.
the coastlines of the Mediterranean Sea remarkably precisely, while the available technology and knowledge in late medieval Europe
would have been insufficient to do so
. The book The Enigma of the Origin of the Portolan Charts
(2016) by Dutch scholar Roel Nicolai
also explores this theme. So how were these charts made so precisely?
Regarding the Arabic numerals: although it is well known
that Europeans acquired their numerals from the Arabs, there is a problem: in Egypt and other Islamic countries, numerals are used
that are different from those now known as Arabic numerals. Why did Europeans not adopt those numerals but others, and where did these
numerals come from? And might the acquisition of the precise nautical charts and Arabic numerals by Europeans perhaps be interlinked?
were the portolans made?
Let us start with the portolans. While studying quadrants and astrolabes used by Europeans for navigation
in the fifteenth century, I became interested in their histories, which stretches all the way back to Greek and Roman antiquity. During
that period, Hipparchus, Ptolemy, and other scholars had already used them for determining celestial altitudes and geographical positions,
most notably latitudes.
Those eminent scholars had already recognized that the world was a globe. They had attempted to measure
its circumference, while they had also realized that geographical positions on the globe could be defined by using a system of latitude
and longitude lines, which could be determined by celestial and geographic measurements.
The Islamic Arabs had further developed
this knowledge using quadrants and astrolabes. A most important determination for Muslims was (and still is) finding the exact direction
to Mecca for daily prayers known as the qibla
. In contrast to Christians, who were –and are– satisfied to orient their churches to
the East, assuming that this is the direction toward Jerusalem, the Islamic peoples were much more precise. They wanted to know their
exact orientation toward Mecca.
This direction could only be established by very precisely measuring both one’s own geographical
position as well as that of Mecca, using the available instruments and mathematics, including the recently introduced compass (originally
from China). Today, determination of the qibla is still done with the aid of qibla compasses
, but now also online
or using qibla
on cell phones.
All of that could be done well only if the correct latitudes and longitudes were known for all these places,
and also more advanced forms of trigonometry that were required to perform the calculations. For many centuries Islamic specialists
developed and maintained this knowledge, while ordinary Muslims fostered a daily geographical awareness that helped them to orient
themselves to Mecca at the required moments.
This implies that at the time the portolans were made, almost the entire Muslim
population must have possessed such a relatively precise geographical awareness, of which, until that time, no parallels may have
existed anywhere else in the world.
Seeking to obtain the precise geographical data needed for determining the qibla must have
improved the Islamic geographical knowledge of the southern and eastern Mediterranean Sea, perhaps to an extent that may not
yet be known to most modern scholars.
In addition, Muslims may not only have charted the territories they lived in, including
large portions of the Iberian Peninsula but perhaps also the lands that they visited all around the Mediterranean. A further exploration
of Islamic scholarship may yield traces of such tables and charts, if they still exist.
Furthermore, most, if not all navigators
that plied that large inland sea must have had an interest in obtaining the best available maps. They may have exchanged such
information voluntary or otherwise, even though many of them may have tried to keep it secret.
Doing all of that would explain
how the famous portolans
emerged, which are far more accurate than the contemporary late-medieval European knowledge and technology
allowed. On such charts, especially the Mediterranean coastlines are mapped with an accuracy almost equal to modern maps, while
the Atlantic coastlines are far less precisely represented
Most notably, the northwestern European coastlines are depicted far
less accurately. At that time, Muslims were, to our knowledge, not yet navigating toward the British Isles, even though some
of their knowledge and technology had gone there. So, in sum, would these portolans perhaps have been constructed using the precise
Islamic geographical knowledge that had been obtained, perhaps first of all, for determining the qibla?
If this hypothesis is
correct, it would suggest rather intensive contacts and exchanges between Muslims, Christians, and others during that period, by wars
and robbery, but quite possibly also by more peaceful encounters and exchanges such as trade or sheer curiosity.
astronomical and geographical advances are well known to specialists in those fields. But these scholars rarely seem to have wandered
outside of their areas of expertise, and may as a result not have considered the diffusion of this knowledge and its effects in the
Mediterranean area and beyond. It may be about time to reunite all these forms of scholarship, perhaps much like what happened when portolans were drawn and used.
As an aside: because latitude and longitude lines are lacking on portolans, this makes one wonder
how these charts were constructed, and what role the very prominent compass roses and associated rhumb lines may have played in doing
so. To my knowledge, this subject may not yet have received the attention it deserves.
What about Arabic numerals?
visiting Egypt in 1979 CE, I did not recognize their numerals easily and had, as a result, to make a quick and determined attempt
to familiarize myself with them, if I wanted to be able to do any successful shopping.
How could that be, I wondered, while in
Europe and elsewhere the current numerals are called Arabic numerals? Why would those Arabs use different ones? Because I encountered
a great many other fascinating questions during that trip to which I did not have any answers, I left this question, together with
many others, on my intellectual back burner for decades.
Clearly, Roman numerals are not very efficient for determining angles
or performing complex trigonometric calculations. Using alphabetical letters as numerals, such as used in Greek, Hebrew, and Arabic
cultures, may have solved that problem to some extent. Yet the introduction of decimal numerals from India, most notably including
the zero, greatly facilitated all of this. This is why in Egypt and elsewhere in the Eastern Arabic world their numerals are still
known as Hindu numerals.
These Hindu numerals were introduced into Italy around 1200 CE by Leonardo Pisano
(Fibonacci) for many
uses, including more efficient bookkeeping. This development is usually credited for the spread of Arabic numerals throughout the
European world. However, Fibonacci used Hindu numerals, and not (what are now known as) Arabic numerals. Where did the Arabic numerals come
from, and how did they overtake the Hindu numerals in Europe, while that apparently did not happen in the Islamic world?
reasons still unknown to me, in Western North Africa, from Modern Lbyia to Morocco, and in Islamic Spain a notation style of
numerals emerged that was different from the Hindu numerals
. Those were the numerals that subsequently spread throughout the North
Atlantic world as Arabic numerals. How and why did that happen?
It would not surprise me if geographic and celestial measurements
as well as calculations performed with quadrants and astrolabes as done in those parts of the world greatly contributed to this trend.
As a result, these numerals may have spread through Islamic Spain, and later, after the reconquista by Catholics, through Northwestern
Europe as part of the Islamic knowledge that the Arabs had left in towns such as Toledo, which as rapidly translated into Latin.
this hypothesis is correct, then one would expect astrolabes from the eastern Islamic world to sport Hindu numerals, while their more
westerly counterparts would exhibit Arabic numbers. One would expect the same trend for written documents, most notably books. Such
an investigation could be executed by examining at all the books and astrolabes that have been preserved in libraries and museums,
as well as by checking the dates, if available, on which they were produced.
My preliminary investigation of astrolabes through
the Internet has very much confirmed this trend. On the British Museum Collection website
this is exactly what can be found, most
notably the Sloane astrolabe
, dating from 1290-1300 CE, which is sporting Arabic numerals, and also this astrolabe
, from 1326 CE.
Both among the oldest known West European astrolabes.
Also this Hispano-Moorish astrolabe
with unknown date of production, possibly
the14th century, shows Arabic numerals, although possibly with a few remnants of the Hindu numerals.
All of this very much confirms
the hypothesis, which was formulated before finding these examples. But a much more systematic and exhaustive study is required to
provide a greater degree of certainty, or a rejection of it.
Yet I am willing to bet some money on the idea that utilizing astrolabes
for celestial and geographic orientation in Europe while employing the great advances made by the Islamic science has very much contributed
to not only introducing Arabic numerals to Europe but also, in doing so, to the emergence of what US scholar Alfred Crosby has called
the unparalleled European ‘quantification of reality
,’ that has provided to so much power over nature as well as over other people.
final question remains: what happened to the Hindu numerals introduced into Italy by Fibonacci? When were they replaced by Arabic
numerals, by whom, and why? I have no good answers yet to these questions.
One final remark: because there can be little or no
doubt that Europeans owe a great deal to Arabic Islamic science, we may want to keep that in mind while dealing with the Arab Islamic
world today, with mutual respect for each other, and for what our societies have contributed to improve life on this planet: our one
and (so far) only home in the cosmos.