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Ptolemy
•
His real name is Claudius Ptolemaeus,
but we know him as Ptolemy. Not
much is known about his life. The
name Claudius probably means he
was a Roman citizen. The name
Ptolemy means that he was Greek.
•
It is believed that he lived from 90 to
170 CE. They know that he worked in
the library of Alexandria, Egypt from
127 to 150 CE.
•
He was an astronomer, mathematician
and geographer.
Discoveries
•
He is famous for his work on
astronomy and geography. His books
were discovered in the Middle Ages,
before the 12th century. They were
 Almagest – the study of
astronomy and geometry
 Tetrabiblios – the study of
astrology
 Geography – which included
maps of how they thought
the world was like at the time
Astronomy
•
Ptolemy believed in the Greek
geocentric view of the universe, that
the Earth was at the center of the
universe. He believed the planets and
sun moved around the Earth in this
order: Mercury, Venus, Sun, Mars,
Jupiter, Saturn.
•
This system is called the Ptolemaic
system. It’s described in his book
Almagest on astronomy.
•
The book has information on the earth,
sun, moon, stars and eclipses. It has a
star catalog of 48 constellations that
we still use today.
Mathematics
•
He was also a mathematician. He
discovered that any quadrilateral
inside a circle with points A B C and D
followed this equation, called
Ptolemy’s theorem:
•
AC*BD = AB*CD + DA*BC
Geography
•
Claudius Ptolemy was very important
in the history of geography and
making maps. His book Geography
was the main one used until
Christopher Columbus. It had 8
volumes.
•
The ancient Greeks and Romans knew
that the earth was round. In his 1st
volume, he shows how to draw a
spherical earth on a flat sheet of
paper. He’s the first known person to
do this.
Geography
•
He was the first person to put a grid
system on the map and he was the
one who invented latitude and
longitude. He was also the first to put
north at the top of the map.
•
The problem was that his map had
many errors because he had to go by
the estimates of merchant travelers
who didn’t know how to measure
longitude at the time.
Geography
•
Ptolemy made the mistake of
assuming that the earth had a shorter
circumference. Because of this,
Christopher Columbus thought he
could reach Asia by sailing west from
Europe. He landed instead in the
NewWorld.
•
Ptolemy made many contributions to
geography. Even the mistake he made
led Columbus to discover America in
1492.
Astrology
•
Ptolemy was also an astrologer. His
book Tetrabiblios was the most
popular book on astrology at the time.
•
He believed that the positions of the
planets at the time of birth did
influence a person, but not completely.
Sources
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http://www.hps.cam.ac.uk/starry/ptolastrol.html
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http://geography.about.com/od/historyofgeography/a/ptolemy.htm
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http://simple.wikipedia.org/wiki/Ptolemy