Photo by Tor Eigeland/sawdia During the extension of the Mosque of Córdoba in 976 under the Spanish Umayyad Caliph al-Hakam ii, this ribbed dome was erected over the mihrab, which indicates the direction of prayer. Entirely covered with glass and gold mosaics, its unique form was probably meant to recall a dome in the Umayyad mosque of Damascus, as were the mosaics, which were said to have been produced by a workman sent by the Byzantine emperor in Constantinople
Written by Sheila S. Blair
and Jonathan M. Bloom
Like minarets, domes are one of the signature forms in Islamic architecture. Since the revelation of Islam in the seventh century of the Common Era until today, they have been used in most—if not all—Islamic lands and cultures. Technically, a dome is a rounded vault, set over a room that is usually square. Builders adopted various means to connect the square room to the dome’s circular base.
Long before Islam, the dome was a popular architectural form throughout the Mediterranean and southwest Asia. Indeed the English word dome derives from the Latin word domus, which means “house.” In Arabic, the most common term for a dome is qubba, which comes from a Syriac word meaning “canopy” or “umbrella”—a reference to the much earlier domical tents of Turkoman and other nomads.
The first major work of Islamic architecture, the Dome of the Rock in Jerusalem, finished in 691 under the sponsorship of the Umayyad caliph ‘Abd al-Malik, is covered by a monumental dome on a wooden frame. A few years later, when his son the Caliph al-Walid had the Prophet Muhammad’s mosque in Madinah reconstructed, a shallow wooden dome was installed over the space in front of the mihrab, to emphasize its importance, and today the Prophet’s Mosque, rebuilt over the centuries, retains this feature. Additionally, the palaces of the Umayyad caliphs in Syria invariably had a domed audience hall, known as a qubbat al-khadra’ or a “dome of heaven.” These three types of domes—commemorative, sacred and royal (or official)—continue to be used in Islamic architecture to this day.
In the Islamic lands and cultures around the Mediterranean, the domed interior was generally regarded as more important than the exterior, which was often either plain or covered with a practical, weather-resistant pyramidal tile roof. Thus the ribbed domes added to the Great Mosque of Córdoba in the 10th century are magnificently decorated on the interior, especially the one on the cover of this calendar, which rises above the front of the mihrab. By the 12th century, the development of the muqarnas, the quintessentially Islamic form of architectural decoration that is often likened to stalactites, gave builders new means of decorating interior vaults. The plaster interior of the Qubbat al-Baadiyyin in Marrakesh combines the Córdoban tradition of ribbed vaults with muqarnas in the corners. Perhaps the most magnificent examples to survive are the two Nasrid muqarnas domes in the Alhambra in Granada, Spain, in which thousands of plaster elements suggest the rotating dome of heaven.
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Written by Paul Lunde
The Hijri calendar
In 638 ce, six years after the death of the Prophet Muhammad, Islam’s second caliph, ‘Umar, recognized the necessity of a calendar to govern the affairs of Muslims. This was first of all a practical matter. Correspondence with military and civilian officials in the newly conquered lands had to be dated. But Persia used a different calendar from Syria, and Egypt used yet another. Each of these calendars had a different starting point, or epoch. The Sasanids, the ruling dynasty of Persia, used June 16, 632 ce, the date of the accession of the last Sasanid monarch, Yazdagird iii. Syria, which until the Muslim conquest was part of the Byzantine Empire, used a form of the Roman “Julian” calendar, with an epoch of October 1, 312 bce. Egypt used the Coptic calendar, with an epoch of August 29, 284 ce. Although all were solar calendars, and hence geared to the seasons and containing 365 days, each also had a different system for periodically adding days to compensate for the fact that the true length of the solar year is not 365 but 365.2422 days.
In pre-Islamic Arabia, various other systems of measuring time had been used. In South Arabia, some calendars apparently were lunar, while others were lunisolar, using months based on the phases of the moon but intercalating days outside the lunar cycle to synchronize the calendar with the seasons. On the eve of Islam, the Himyarites appear to have used a calendar based on the Julian form, but with an epoch of 110 bce. In central Arabia, the course of the year was charted by the position of the stars relative to the horizon at sunset or sunrise, dividing the ecliptic into 28 equal parts corresponding to the location of the moon on each successive night of the month. The names of the months in that calendar have continued in the Islamic calendar to this day and would seem to indicate that, before Islam, some sort of lunisolar calendar was in use, though it is not known to have had an epoch other than memorable local events.
There were two other reasons ‘Umar rejected existing solar calendars. The Qur’an, in Chapter 10, Verse 5, states that time should be reckoned by the moon. Not only that, calendars used by the Persians, Syrians and Egyptians were identified with other religions and cultures. He therefore decided to create a calendar specifically for the Muslim community. It would be lunar, and it would have 12 months, each with 29 or 30 days.
This gives the lunar year 354 days, 11 days fewer than the solar year. ‘Umar chose as the epoch for the new Muslim calendar the year of the hijra, the emigration of the Prophet Muhammad from Makkah to Madinah, where Muslims first attained religious and political autonomy. The hijri epoch thus began on 1 Muharram of the year 1 according to the Islamic calendar, which corresponds to July 16, 622 ce, on the Gregorian calendar. Today in the West, it is customary, when writing hijri dates, to use the abbreviation ah, which stands for the Latin anno hegirae, “year of the hijra.”
Because the Islamic lunar calendar is 11 days shorter than the solar, it is therefore not synchronized to the seasons. Its festivals, which fall on the same days of the same lunar months each year, make the round of the seasons every 33 solar years. This 11-day difference between the lunar and the solar year accounts for the difficulty of converting dates from one system to the other.
The Gregorian calendar
The early calendar of the Roman Empire was lunisolar, containing 355 days divided into 12 months beginning on January 1. To keep it more or less in accord with the actual solar year, a month was added every two years. The system for doing so was complex, and cumulative errors gradually misaligned it with the seasons. By 46 bce, it was some three months out of alignment, and Julius Caesar oversaw its reform. Consulting Greek astronomers in Alexandria, he created a solar calendar in which one day was added to February every fourth year, effectively compensating for the solar year’s length of 365.2422 days. This Julian calendar was used throughout Europe until 1582 ce.
In the Middle Ages, the Christian liturgical calendar was grafted onto the Julian one, and the computation of lunar festivals like Easter, which falls on the first Sunday after the first full moon after the spring equinox, exercised some of the best minds in Christendom. The use of the epoch 1 ce dates from the sixth century, but did not become common until the 10th.
The Julian year was nonetheless 11 minutes and 14 seconds too long. By the early 16th century, due to the accumulated error, the spring equinox was falling on March 11 rather than where it should, on March 21. Copernicus, Christophorus Clavius and the physician Aloysius Lilius provided the calculations, and in 1582 Pope Gregory xiii ordered that Thursday, October 4, 1582, would be followed by Friday, October 15, 1582. Most Catholic countries accepted the new “Gregorian” calendar, but it was not adopted in England and the Americas until the 18th century. Its use is now almost universal worldwide. The Gregorian year is nonetheless 25.96 seconds ahead of the solar year, which by the year 4909 will add up to an extra day.
Paul Lunde (email@example.com) is a senior research associate with the Civilizations in Contact Project at Cambridge University. His most recent publication, with co-author Caroline Stone, is Ibn Fadlan and the Land of Darkness: Arab Travellers in the Far North (Penguin, 2012). He lives in Seville and Cambridge, England.