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Greek scientists
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We know almost nothing about Thales
of Miletus. Later generations told many anecdotes about
this wise man, but it is difficult to verify the reliability of these stories.
What seems certain is that he predicted the solar eclipse of 28 May 585,
which was remembered because the Lydian
king Alyattes
and the Median
leader Cyaxares
were fighting a battle on that day. Another reliable bit of information
is that he did some geometrical research, which enabled him to measure
the pyramids. However, his most important contribution to physics and philosophy
is his attempt to give non-religious, rational explanations for physical
phenomena. Behind the phenomena was not a catalogue of deities, but one
single, original principle. Although his hypothesis that this principle
was water is rather unfortunate, his idea to look for deeper causes was
the true beginning of philosophy and science. |
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Democritus
of Abdera proposed that matter was made up from atoms.
There was no real evidence for this idea (which was not completely new),
but is explained why change was possible. The atoms were always moving
and clustering in various, temporary combinations. Therefore, things seemed
to change, but 'not being' never changed into 'being'. (It was assumed
that 'not being' was a vacuum, which means that it is in fact not a 'not
being' because a vacuum exists in at least four dimensions.) The consequence
of this idea is that we are allowed to use our senses, although Democritus
warns us to be careful. |
Musei Capitolini, Roma
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Hardly anything is known about Hippocrates
of Cos, except for the fact that his reputation as the
greatest physician of all times had already been firmly established in
the fourth century. It is likely that he was born in 460, but the year
of his death is a mystery, although 377 has been mentioned. Not even his
own writings can be used to gain knowledge about the man, because the
Corpus Hippocraticum was collected in the second century, and contains
spurious material. However, it is certain that Hippocrates made medicine
an independent discipline and did much for its professionalisation. One
of his principles was that one could not study an illness in isolation,
but had to study the patient as a whole. For several diseases, he discovered
the cause in a wrong way of life. |
Kérylos Villa,
Beaulieu
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The most famous student of the Athenian philosopher Plato
was the Macedonian
scientist Aristotle
of Stagira (384-322). After the death of his master, he
studied biology and accepted a position as teacher of the Macedonian crown
prince Alexander.
When the Macedonians subdued Greece, Aristotle founded a school at Athens.
Most of his writings are lost; what remains are his lecture notes, which
were rediscovered in the first century BCE. During the last decades, scholars
have started to re-examine the fragments of the lost works, which has led
to important changes in our understanding of Aristotle's philosophy. However,
the accepted view remains that he replaced his master's speculations with
a more down-to-earth philosophy. His main works are the Prior Analytics
(in which he described the rules of logic), the Physics, the Animal
History, the Rhetorics, the Poetics, the Metaphysics,
the Nicomachean Ethics, and the Politics. All these books
have become classics, and it is not exaggerated to say that Aristotle is
the most influential philosopher of all ages and the founder of modern
science. |
Archaeological museum,
Palermo
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The great mathematician Euclid
is said to have lived c.300 BCE and was connected to the Museum at Alexandria,
a scientific institute created by king Ptolemy
I Soter. In the thirteen books of the
Elements, Euclid summarized
and systematized all mathematic knowledge of his age. He also published
works on optics and the theory of music. However, he is best known as a
mathematicst. No work of ancient art approaches the pure and surprising
beauty of Euclid's proof that there are infinitely many prime numbers. |
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Aristarchus
of Samos (c.310-c.230 BCE) was the first to catch a glimpse
of the immense size of the universe. Until then, everyone had believed
that the moon, sun, planets, and stars all revolved around the earth. Perhaps
the stars were as far away as twenty of forty radiuses of the earth, perhaps
hunderd or thousand (the maximum size according to Archimedes),
but nobody thought that it would be much bigger. But Aristarchus argued
that the sun was about nineteen times the size and distance of the moon.
The consequence of his calculation was that the sun was larger than the
earth, and this in turn led to the conclusion that it was possible that
it was not the sun, but the earth that was moving. Although several ancient
astronomers, a.o. Seleucus of Babylon,
subscribed to this correct interpretation of the phenomena, it was ignored
until Copernicus. The correctness was not proven until Bessel in 1839 measured
the parallax. |
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One of the most original thinkers of Antiquity was Archimedes
of Syracuse (287-212). Because our approach to physics
is based upon a model that was developed by this scientist, we immediately
recognize him as 'one of us'. And indeed: he did all kinds of experiments
and brought the results together in a law of physics - the famous Law of
Archimedes. He was also interested in mathematics, which led to a new approximation
of pi and a remarkable treatise, The sand-reckoner, in which
he showed that he could command really big numbers by calculating the number
of grains of sand in the universe. Archimedes was also interested in engineering
and invented a hydraulic organ and a planetarium (which implies that he
thought that the motions of heaven could be described as if they were mechanical).
The invention of a machine to lever ships from a dock to the sea made him
boast that if he only had a point to stand on, he would move the earth.
When Roman general Marcellus
besieged Syracuse, Archimedes invented war machines. During the sack of
the city, he was killed (text). |
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One of the students of the great poet Callimachus
of Cyrene was Eratosthenes
of Cyrene (c.275-192 BCE), who became librarian in the
Museum, the scientific institute of Alexandria. He invented a new method
to calculate prime numbers, drew a famous world map, catalogued several
hundreds of stars, but became especially famous for his calculation of
the circumference of the earth, based on the angle of the shadow that the
sun made over a vertical pole at Alexandria at noon and the fact that at
the same time, the sun light fell straight into a well as Syene in southern
Egypt. He concluded that the circumference was 45,460 kilometers, which
is pretty close to the real figure. He also wrote a treatise on chronology
and a book on musical theory, composed poems and comedies, and was responsible
for two dictionaries and a book on grammar. As an ethnologist, he suggested
that the common division between civilized people and barbarians was invalid
(text).
Eratosthenes was nicknamed bêta or 'number two', because in
no branch of science he was ever the best, although he excelled in nearly
every one of them. |
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The stellar catalogue made by Hipparchus
of Nicaea contains observations that can be dated to 162-128
BCE, and this gives us an indication about the period in which he lived.
Unfortunately, this is about everything we know about this astronomer,
who was the first to discover the precession, i.e. the slow reorientation
of the earth's axis. He was able to do this because he possessed the sky
map of Eratosthenes and age-old Babylonian
observations and knew the theories of the great Kidinnu.
Unfortunately, Hipparchus ignored Kidinnu's calculation of the length of
the solar year. The Greek astronomer's estimate had an error of 6½
minutes, whereas the Babylonian was only 4½ short of the real length
of the year. Nevertheless, Hipparchus was able to improve the calendar.
Another triumph was the accurate calculation of the distance to the moon,
and the improvement of the world map of Eratosthenes. |
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Strabo
of Amasia (c.62 BCE - c.24 CE) is the author of one of
the largest works of geography from Antiquity. His mother's family had
been important during the reign of king Mithridates
VI of Pontus, but during the war against the Roman general Pompey,
it had switched sides. This loyalty provided Strabo with connections in
the Roman world. The seventeen books of his Geography are partially
based upon autopsy (Asia Minor, Greece, Italy, Egypt), and partially on
good sources like Polybius
of Megalopolis and Megasthenes (who had visited India). The
books are written in a simple Greek, but are more entertaining than other
ancient works of geography. |
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Like Aristarchus, Eratosthenes, and Hipparchus,
Ptolemy
of Alexandria (c.85-c.165) was interested in both geography
and astronomy. On both subjects, he published important works. His astronomical
book was called the Megalê Syntaxis, the 'big explanation'.
It is a summary of all astronomical knowledge of his age, and it remained
the most important work on this subject until the sixteenth century, especially
because he gave mathematical explanations of the phenomena. After Antiquity,
the Arabs translated it and called it
Almagest, under which name
it is still known. In his Tetrabiblos, Ptolemy explained the importance
of astrology, and told how the stars influenced countries and individuals.
In the eight books of his Geography, he deals with map making and
describes the entire known earth. It remained one of the most important
works until 1488, when Bartolomeus Diaz reached the Cape of Good Hope and
proved that Ptolemy's statement that one could not circumnavigate Africa
was simply wrong. |
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Galen
of Pergamon (129-216) started his career as physician of
gladiators, but he became court physician of the Roman emperors Marcus
Aurelius, Commodus,
and Septimius
Severus. He published many books, which he had to rewrite after his
library was destroyed by fire in 191. These book became extremely influential
in the Middle Ages, when they were well-read in both the Byzantine empire
and the Arab world. Great scientists like Ibn Sina, Ibn Rushd and Vesalius
based their researches on the foundations laid by Galen. Being both a doctor
and a writer, he was rather indiscreet, but on the other hand: we now have
the entire medical status of two emperors. |
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