Timekeeping
& Clocks
The
Islamic Calendar
The
Islamic calendar (or Hijri calendar) is a purely lunar
calendar. It contains 12 months that are based on the
motion of the moon, and because 12 synodic months is only
12 x 29.53=354.36 days, the Islamic calendar is consistently
shorter than a tropical year, and therefore it shifts
with respect to the Christian calendar.
The
calendar is based on the Qur'an (Sura IX, 36-37) and its
proper observance is a sacred duty for Muslims.
The
Islamic calendar is the official calendar in countries
around the Gulf, especially Saudi Arabia. But other Muslim
countries use the Gregorian calendar for civil purposes
and only turn to the Islamic calendar for religious purposes.
What
is Taught: Until the 14th century, the only
type of clock available was the water clock. In 1335,
a large mechanical clock was erected in Milan, Italy.
This was possibly the first weight-driven clock.
What
Should be Taught: A variety of mechanical clocks
were produced by Spanish Muslim engineers, both large
and small, and this knowledge was transmitted to Europe
through Latin translations of Islamic books on mechanics.
These
clocks were weight-driven.
Designs
and illustrations of epi-cyclic and segmental gears were
provided. One such clock included a mercury escapement.
The
latter type was directly copied by Europeans during the
15th century. In addition, during the 9th century, Ibn
Firnas of Islamic Spain, according to Will Durant, invented
a watch-like device which kept accurate time.
The
Muslims also constructed a variety of highly accurate
astronomical clocks for use in their observatories.
What
is Taught: In the 17th century, the pendulum
was developed by Galileo during his teenage years. He
noticed a chandelier swaying as it was being blown by
the wind. As a result, he went home and invented the pendulum.
What Should be Taught: The
pendulum was discovered by Ibn Yunus al-Masri during the
10th century, who was the first to study and document
its oscillatory motion.
Its
value for use in clocks was introduced by Muslim physicists
during the 15th century.
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