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PYTHAGORAS
c.570–495 BCE
Little is known for certain about
the life of the Greek mathematician
Pythagoras, who did not leave
behind any written work. He was
born on the Greek island of Samos,
but left some time before 518 BCE for
Croton in southern Italy, where he
founded a secretive philosophical
and religious society called the
Pythagoreans. The society’s
inner circle called themselves
mathematikoi, and held that reality,
at its deepest level, is mathematical
in nature. Pythagoras believed that
the relations between all things
could be reduced to numbers, and
his group began discovering these
relations. Among his many
contributions to science and
mathematics, Pythagoras studied
the harmonics of vibrating strings,
and probably provided the first
proof of the theorem that now bears
his name: that the square of the
hypotenuse on a right-angled
triangle is equal to the sum of the
squares of the other two sides.
See also: Archimedes 24–25
ARYABHATA
476–550 CEWorking in Kusumapura, a center
of learning in India’s Gupta empire,
the Hindu mathematician and
astronomer Aryabhata wrote a
short treatise that was to prove
highly influential among later
Islamic scholars. Written in verse
when he was just 23 years old, the
Arabhatiya contains sections on
arithmetic, algebra, trigonometry,
and astronomy. It includes an
approximation of pi (π, the ratio
of a circle’s circumference to its
diameter) as 3.1416, which is
accurate to four decimal places,
and of Earth’s circumference as
24,835 miles (39,968km)—very
close to the current accepted
figure of 24,902 miles (40,075km).
Aryabhata also suggested that the
apparent movement of the stars
was due to the rotation of Earth and
that the orbits of the planets were
ellipses, but appears to have fallen
short of proposing a heliocentric
model of the solar system.
See also: Nicolaus Copernicus
34–39 ■ Johannes Kepler 40–41DIRECTORY
F
rom its roots with individuals or small groups working mostly in
isolation, often in pursuit of quasi-religious goals, science has been
transformed into a practical activity that is central to the working
of modern society. Today, many projects are highly collaborative in nature,
and it can be hard—and indeed invidious—to pick out particular figures.
More areas of research exist than ever before, and the boundaries
between disciplines are becoming blurred. Mathematicians provide
solutions to the problems of physics and physicists explain the nature of
chemical reactions, while chemists delve into the mysteries of life and
biologists turn their attention to artificial intelligence. Here, we list just
some of the figures who have added to our understanding of the world.XENOPHANES
c.570–475 BCEXenophanes of Colophon was an
itinerant Greek philosopher and
poet. His wide-ranging interests
reflected the knowledge he
gained from careful observations
made on his extensive travels.
He identified the energy of the
Sun that heats the oceans to
create clouds as the driving
force behind physical processes
on Earth. Xenophanes thought
that clouds were the origin of
heavenly bodies: the stars were
burning clouds, while the Moon
was made of compressed cloud.
Upon discovering the fossilized
remains of sea creatures far
inland, he reasoned that Earth
alternated between periods of
flood and drought. Xenophanes
produced one of the earliest
accounts of natural phenomena
that did not invoke divine forces
to explain them, but his works
were largely neglected in the
centuries after his death.
See also: Empedocles 21 ■
Zhang Heng 26–27