19
Chinese astronomers observed a
supernova, which was identified
as the Crab Nebula in 1731.
Some of the most advanced
technology in the first millennium
CE, including the spinning wheel,
was developed in India, and
Chinese missions were sent to
study Indian farming techniques.
Indian mathematicians developed
what we now call the “Arabic”
number system, including negative
numbers and zero, and gave
definitions of the trigonometric
functions sine and cosine.The Golden Age of Islam
In the middle of the 8th century,
the Islamic Abbasid Caliphate
moved the capital of its empire from
Damascus to Baghdad. Guided by
the Quranic slogan “The ink of a
scholar is more holy than the bloodof a martyr,” Caliph Harun al-Rashid
founded the House of Wisdom in
his new capital, intending it to be
a library and center for research.
Scholars collected books from the
old Greek city states and India and
translated them into Arabic. This
is how many of the ancient texts
would eventually reach the West,
where they were largely unknown
in the Middle Ages. By the middle
of the 9th century, the library in
Baghdad had grown to become
a fine successor to the library
at Alexandria.
Among those who were inspired
by the House of Wisdom were
several astronomers, notably al-Sufi,
who built on the work of Hipparchus
and Ptolemy. Astronomy was of
practical use to Arab nomads for
navigation, since they steered their
camels across the desert at night.Alhazen, born in Basra and
educated in Baghdad, was one of
the first experimental scientists,
and his book on optics has been
likened in importance to the work
of Isaac Newton. Arab alchemists
devised distillation and other new
techniques, and coined words such
as alkali, aldehyde, and alcohol.
Physician al-Razi introduced soap,
distinguished for the first time
between smallpox and measles,
and wrote in one of his many books
“The doctor’s aim is to do good,
even to our enemies.” Al-Khwarizmi
and other mathematicians invented
algebra and algorithms; and
engineer al-Jazari invented the
crank-connecting rod system,
which is still used in bicycles and
cars. It would take several centuries
for European scientists to catch up
with these developments. ■THE BEGINNING OF SCIENCE
C.240 BCE
C.230 BCE
C.13 0 BCE C.15 0 CE 964
C.120 CE 628 1021
Eratosthenes, a friend of
Archimedes, calculates
the circumference of
Earth from the shadows
of the Sun at midday on
midsummer day.
Ctesibius builds
clepsydras—water
clocks—that remain for
centuries the most
accurate timepieces
in the world.Hipparchus discovers
the precession of
Earth’s orbit and
compiles the Western
world’s first star
catalogue.Claudius Ptolemy’s
Almagest becomes the
authoritative text on
astronomy in the
West, even though it
contains many errors.Persian astronomer,
Abd al-Rahman
al-Sufi updates the
Almagest, and gives
many stars the
Arabic names
used today.In China, Zhang Heng
discusses the nature of
eclipses, and compiles
a catalogue of
2,500 stars.Indian mathematician
Brahmagupta outlines
the first rules to use
the number zero.Alhazen, one of the
first experimental
scientists, conducts
original research on
vision and optics.