Download History of Astronomy

History of Astronomy
Day Three
Greek Astronomy
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About 624 BC to 547 BC
One of the earliest
Greek philosophers.
His areas of interest
included geometry and
astronomy.
There are no books or
writings that have
survived from Thales.
Used Babylonian records to predict eclipses
 One of the first people to try to look at the skies in a
purely scientific way.
 Believed that islands appear to float, so the earth must
float upon a body of water.
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Greek Astronomy
Anaximander
2600 Years Ago
610 - 545 B.C.
• Founder of Astronomy
•Introduced Geometry
and Mathematical
Proportions in Mapping
the Heavens
Anaximander
• Theories departed from more mystical concepts of the universe
• Rejected the older notion that the Earth was suspended or supported
from elsewhere in the heavens
• Earth remained in its unsupported position at the
center of the universe because it had no reason to
move in any direction and therefore was at rest.
Anaximander
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He is believed to have been the first person to propose that the
Sun and the planets orbit the Earth and the universe is infinite.
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But he also believed that the Sun, moon, stars and planets were
actually in the shape of wheels and were surrounded by fire
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Pythagoras’ teacher
Greek Astronomy
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About 569 BC to 475 BC
One of the greatest
mathematicians of all time.
Pythagoras and his followers
believed that everything was
related to mathematics
Founded secret society
based on his mathematical
discoveries and their
religious implications.
Mixed ancient mythology
with scientific empiricism
Greek Astronomy
Pythagoras
• Described the earth as a sphere (using shadow Earth casts on the moon
during eclipses)
• Rather than being wheels on fire, the five known planets were actually
suspended inside crystalline spheres – each of which producing a
separate musical note
There are 7 notes on
a scale and 7 planets
had been discovered,
so Pythagoras thought
these ideas were
related.
• First to announce that the Moon’s orbit was inclined to the earth’s equator.
Greek Astronomy
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427 BC to 347 BC
Well known for political and social
philosophy but he also made
contributions to astronomy.
He was most noted for his belief in the
perfect and unchanging nature of
the heavens.
Plato was the head of the School of
Athens & was Aristotle’s teacher.
Greek Astronomy
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The Earth was a sphere,
stationary at the center of
the Universe.
The stars and planets were
carried around the Earth
Moon, Sun, Venus,
Mercury, Mars, Jupiter,
Saturn, fixed stars. (in
order, outwards from the
center)
Greek Astronomy
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384 BC to 322 BC
Founded his own school called the Lyceum in Athens –
ironic because he was pretty much wrong about
everything that he taught.
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Aristotle was a philosopher (especially logic). Math was
his weakness, therefore he decided that evidence was
unnecessary to prove ideas.
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He was not a scientist.
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In fact, he set back science for about 2,000 years.
Greek Astronomy
Things that Aristotle got wrong:
Chemistry
Physics
Biology
Astronomy
Psychology
Basic Human Rights (women are deficient, deformed and monstrous
. . . and have fewer teeth (also wrong)
Early Greek Theory
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The “Geocentric Model” solved & accurately predicted:
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Motion of the Sun and Moon
Early Greek Theory
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The “Geocentric Model” solved & accurately predicted eclipses
Greek Astronomy
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About 325 BC to 265 BC
Great mathematician
Because of him, we start to see more
math incorporated into Astronomy
Greek Astronomy
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About 310 BC to 230 BC
We have no writings that have survived but
Aristarchus is referred to in the writings of other
philosophers
Best known for proposing a Heliocentric universe,
where the sun is at the center and the planets
Greek Astronomy
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Aristarchus is the first to attempt to measure the relative distance
between the Earth-Moon and the Earth-Sun without the aid of
trigonometry.
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He was 2 degrees off
Greek Astronomy
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276 BC to 194 BC
Librarian at the Great Library of Alexandria in Egypt.
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Developed a calendar with a leap year.
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Measured the circumference of the Earth in 325 BC !!
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Achieved an accuracy of about 90% of the actual
number.
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Greek Astronomy
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190 BC to 120 BC
Hipparchus is considered the first great astronomer and scientist
Hipparchus is one of the first of the ancient philosophers to realize that
ideas must be proven.
He realized that more data meant more certainty in the idea or model
Based on measurements during an eclipse, he is able to place an
accurate range on the distance to the moon.
Greek Astronomy
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Created highly accurate star atlases in an attempt to measure the length
of the year more accurately.
He measured the length of the year to within 6.5 minutes of the actual
time.
He discovered precession by examining ancient star position data (mostly
Mesopotamian) and comparing them to his own measurements.
Greek Astronomy
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About 85 AD to 165 AD
Ptolemy is the most influential astronomer in
his day and his (inaccurate) models of the
universe will prevail for the next 1400 years
He is a great admirer of Hipparchus and his
rigorous method of verifying ideas with
empirical data.
Ptolemy is also accused of stealing ideas
without crediting his source. 
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Ptolemy believes in the geocentric model.
He saw that there were problems with Aristotle’s geocentric model.
Ptolemy decided to use epicycles to explain better predict where the planets
should be in the sky.
Although he was able to make more accurate predictions than previous
astronomers, his model still failed to be completely accurate.