Download history of astro outline 2014

HISTORY OF ASTRONOMY OUTLINE
Beginnings
3000 BC
Ancient Babylonians develop number system based on 60
(led to time-keeping and angular measurements) and 12month calendar.
Ancient Egyptians separated a day-night period into 24
separate hours and the year into 365 days
2150 BC
Stonehenge—entrance stones are lined up so it would be
possible to see the sunrise on the summer solstice. Likely that
Neolithic tribes were responsible for construction.
2136 BC
Ancient Chinese—recorded observations of the night sky;
eclipses and comets and supernovae were observed.
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These peoples actively practiced astronomy by attempting to
understand and quantify their surroundings.
Most cultures developed a geocentric view of the universe, based
upon the apparent east to west motion of the stars, Sun and moon.
Pythagoras and the Ancient Greeks
550 BC
Pythagoras of Samos began using mathematics to describe
natural phenomena.
350 BC
Aristotle supported the geocentric view and he had
influence. He also had views about the cosmos and
considered the Earth to be spherical, based upon
observations during lunar eclipses.
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Aristotle’s other views are worth noting:
o Four elements (Earth, fire, air and water)
o Five known planets were fixed to crystalline spheres
encased in a celestial sphere containing all stars.
o The heavenly objects were composed of a fifth
element called quintessence.
o Each of the spheres revolved around the Earth in
perfect circles.
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o Earth was subject to birth, decay and death
(imperfection) while the heavens were pure,
unblemished and unchanging (perfection).
o Aristotle also believed that an object stays in motion
because a force is constantly pushing it.
o Inconsistencies were recognized by the Chinese,
reported blemishes such as moving objects with tails
(comets) and bright lights that appear and disappear
(supernovae). Also, the sometimes backwards motion
(retrograde motion) of planets Mars, Jupiter and Saturn
was not explained by the geocentric view.
270 BC
Aristarchus of Samos expressed a different point of view. He
proposed a sun-centered universe (e.g., heliocentric).
200 BC
Erathosthenes devised a method to measure the
circumference of the Earth.
200 BC
Hipparcus refined the geocentric model using epicycles.
125 AD
Last of the great Greek astronomers, Ptolemy of Alexandria,
Egypt expounded upon previous theories about the motion
of the planets and firmly defended the geocentric model of
the universe. Ptolemy’s work included:
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Claudius Ptolemy proposes an Earth-centered (geocentric)
model of the universe in his work called Almagest. His work
supported Aristotle’s geocentric view of the universe.
To address the problem of retrograde motion of Mars, Jupiter
and Saturn, Ptolemy used a complex system of epicycles. As
the planet circled the Earth, it also had a mini-orbit around a
point on the larger orbital circle. The solution used perfect
circles.
Understanding of astronomy increased as the usage of
mathematics, direct observation and logical reason increased.
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From 1st Century AD to 16th Century AD
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Limited input from western world.
Continued Middle Eastern input.
No significant advances in understanding or technology to unglue
the adherence to the geocentric model of the universe.
Little progress was made until the 16th century. What was responsible for
this 14-century gap (the Middle Ages)—a scientific lull lifted by the
advancement of new technologies.
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The printing press: dissemination of knowledge through printed
material became part of the public domain.
The telescope: pushing the boundaries of our universe to new
places. Subsequent observations led individuals to alter their
understanding of the universe.
Mathematics became a predictive tool, useful in explaining the
orbits of the planets.
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Astronomical observations were used to develop theories.
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Baywatch and Jersey Shore (Just checking if you are reading)
16th Century AD (Renaissance)
By the 1500’s, the geocentric model did not accurately predict the
motion of the planets. Variations that seemed tiny in the 2nd century grew
into significant deviations and greatly lessened the predictive ability of the
geocentric model. This demanded an explanation.
1500 AD
The geocentric view survived until the European renaissance
in the 1500’s, when Nicolas Copernicus proposed a Suncentered (heliocentric) model of universe. His work
supported Aristarchus’s heliocentric view of the universe.
Copernicus was looking for a simpler model (Occam’s Razor).
1593 AD
Copernicus had his heliocentric model published in his work
called De Revolutionibus Orbium Coelestium. He died within
days after receiving the first copy of its publication.
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In his work, Copernicus concluded the following:
 Mercurys and Venus, since they appear closest to the Sun,
have orbits inside the Earth’s orbit.
 Mars, Jupiter and Saturn, since they appear high in the
night sky, have orbits outside the Earth’s orbit.
 The configuration (or orbit) of each planet.
 The measurement of each planet’s sideral and synodic
period.
 The calculated distance of each planet to the Sun.
1576 AD
Danish king Frederick II built Tycho Brahe an astronomical
observatory called Uraniborg. Brahe begins to catalog his
observations of the stars and planets using devices that
accurately measure position and angle of stars and planets
as viewed with the unaided eye.
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1600 AD
At Uraniborg, Brahe made numerous observations and
recorded the most accurate measurements of
astronomical objects up to this time.
Brahe used his observatory to measure the positions of
astronomical objects for 21 years. Greatest collection of
astronomical observations at the time.
Johannes Kepler joined Tycho Brahe and gained access to
Brahe’s entire volume of astronomical observations. He used
these observations to deduce three laws concerning
planetary orbits and proved that planetary orbits occur not in
perfect circles, but in ellipses.
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Brahe had Kepler join him at Uraniborg in 1600, after
reviewing Kepler’s mathematical predictions of the
planetary orbits published earlier in 1596.
Johannes Kepler solves the problem of the irregular orbits
of the planets by showing that planets orbit in ellipses, not
perfect circles. He establishes three laws to describe
planetary motion. Kepler used Brahe’s comprehensive
astronomical measurements to solve the puzzle.
Kepler’s laws could only explain how the planets move,
but not why.
1608 AD
Hans Lippershey from the Netherlands invented the
telescope.
1609 AD
Galileo Galilei constructs a telescope and uses it to make a
series of discoveries that contradicted the geocentric model,
Aristotle and the Roman Catholic Church.
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About Galileo’s contributions:
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Galileo supports the heliocentric model with his
observations
Galileo used the telescope to make observations of the
heavens. His observations supported the heliocentric view
of the universe
1. Phases of Venus: Venus had phases just like the
Moon (the change in the apparent size of Venus
was related to the planet’s phase)
2. The orbit of Jupiter’s moons: Jupiter’s moons
(Galileo observed the location of the four moons of
Jupiter over time, and concluded that they are
orbiting Jupiter because they move across from one
side of the planet to the other).
3. Imperfections on the Moon’s surface: The Moon’s
surface was irregular and crater-filled
4. Dark spots on the Sun: The Sun was observed to
have dark spots
These observations began to erode the notion of celestial perfection and
provided support for the heliocentric view of the universe.
Of course, Galileo’s view was in conflict with Aristotle and the Roman
Catholic Church, who accepted only the geocentric view. Galileo had
to recant his support of the heliocentric view and was placed under
house arrest for the remainder of his life for “vehement suspicion of
heresy.” (Without a good word put in by a friend with influence in the
papal circles, Galileo might have had to endure the Inquisition’s notorious
and, at that time, legal investigative process—torture, confession and,
quite often, death.)
Galileo’s observations provided support for the heliocentric model, but he
was limited by life’s circumstances (house arrest and his health).
1687 AD
Sir Isaac Newton publishes his major work on forces and
gravity called Philosophiae Naturalis Principia Mathematica.
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1704 AD
Sir Issac Newton figures out the planets are moving under the
influence of gravitational force, which supports Kepler’s
findings.
Newton created a mathematical description of how gravity
behaved and determined it to be a universal force, meaning
that all motion in the universe was governed by gravity.
Newton publishes his experiments and theories about light
and color called Optiks. He laid the groundwork for the
understanding of the true nature of light, which is how the
composition of the universe is determined.