The Sun

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Pythagorean Paradigm

• The planets, Sun, Moon and stars move in
  perfectly circular orbits
• The speed of the planets, Sun, Moon and stars in
  their circular orbits is perfectly uniform
• The Earth is at the exact center of the motion
  of the celestial bodies.
• Plato was teaching this geocentric view of the
  universe.
• Only Aristarchus, one of his students, dared to
  oppose this view putting the Sun at the center of
  the universe, but his view was not accepted by
  the Greeks.

2
Platos Reasoning

1. The Earth is not part of the heavens.
2. The celestial objects are bright points of light
   while the Earth is an immense, nonluminous sphere
   of mud and rock.
3. The Greeks saw little change in the heavens---the
   stars are the same night after night. In contrast
   to this, they saw the Earth as the home of birth,
   change, and destruction.
4. Finally, our senses show that the Earth appears
   to be stationary! Air, clouds, birds, and other
   things unattached to the ground are not left
   behind as they would be if the Earth was moving.
   There should be a strong wind if the Earth were
   spinning as suggested by some radicals.

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Retrograde motion
Ordinarily, planets will wander eastwards among
the stars. But sometimes they slow down, stop and
start to move westwards. Then they stop, start to
move eastward again. And when this happens, the
planets appear brighter. This retrograde motion
has been one of the biggest mysteries of
antiquity.
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Epicycles
Aristotles model geocentric universe planets
moving around the Earth on crystalline
spheres. Ptolemy Refined Aristotles model with
the addition of epicycles. Almagest 13 volume
set of astronomy Stood for 1500 years
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Occams Razor
By the 16th century the following paradigm had
developed Man is God's special creation of the
physical universe the Earth is the center of a
mathematically-planned universe and we are given
the gift of reading this harmony. Scientists use
a guiding principle called Occam's Razor to
choose between two or models that accurately
explain the observations. the best model is the
simplest one---the one requiring the fewest
assumptions and modifications in order to fit the
observations. Guided by Occam's Razor some
scientists began to have serious doubts about
Ptolemy's geocentric model in the early days of
the Renaissance.
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Copernicus
Ptolemaic model was un-Godlike. Life-giving force
should be at the center of the universe ? Sun
gives life, so Sun must be at the center Inner
planets are faster, outer planets are slower ?
explains the retrograde motion of the planets
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Giardano Bruno
Bruno (1548 February 17, 1600), was an Italian
Dominican friar, philosopher, mathematician and
astronomer, who is best known as a proponent of
the infinity of the universe. His cosmological
theories went beyond the Copernican model in
identifying the Sun as just one of an infinite
number of independently moving heavenly bodies
he is the first European to have conceptualized
the universe as a continuum where the stars we
see at night are identical in nature to the Sun.
He was burned at the stake by civil authorities
in 1600 after the Roman Inquisition found him
guilty of heresy and turned him over to the
state, which at that time considered heresy
illegal.
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Tycho Brahe
Great astronomer before the invention of the
telescope. Believed in the Ptolemaic theory, and
made measurements to prove the theory. Stars must
be at least 700 times more distant than
Saturn. Made his observations on Uraniborg, small
island in Denmark. In 1600, Kepler became his
student.
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Johannes Kepler
He was hired by Tycho to work on the geocentric
theory. After the death of Tycho, he started
working as the court matematician to Bavaria. He
had all of Tychos data to work with. In 20 years
he developed three laws, simple and obvious for
us, but a major revolution for his time.
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Keplers Laws
Both Copernican and Ptolemaic theories agreed on
one major point God was perfect ? God created
the universe ? the universe must be perfect The
circle is the perfect shape ? whatever was
rotating around whatever else, the orbit must be
a circle.
Keplers First Law Planetary orbits are ellipses
with the Sun at one focus.
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Keplers Laws II
Keplers Second Law a line between the planet
and the Sun sweeps out equal areas in equal
times A planets speed changes with its distance
from the Sun. Keplers Third Law (a planet's
period of revolution in years)2 (semimajor axis
of its orbit in A.U.)3.
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Galileo
Galileo Galilei (1564 1642) was an Italian
physicist, mathematician, astronomer and
philosopher who played a major role in the
Scientific Revolution. His achievements include
improvements to the telescope and consequent
astronomical observations, and support for
Copernicanism.
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Galileo
Controversy with Father Orazio Grassi over the
nature of the comets. Observed the craters on the
Moon ? Moon was not perfect. Observed Jupiters
moons ? Jupiter also had moons. Venus had phases
just like the moon ? Ptolemaic theory did not
allow this.
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Galileo
Galileo's championing of Copernicanism was
controversial within his lifetime, when a large
majority of philosophers and astronomers still
subscribed to the geocentric view. After 1610,
when he began publicly supporting the
heliocentric view, he met with bitter opposition
from some philosophers and clerics, and two of
the latter eventually denounced him to the Roman
Inquisition early in 1615. In February 1616,
although he had been cleared of any offence, the
Catholic Church nevertheless condemned
heliocentrism as "false and contrary to
Scripture", and Galileo was warned to abandon his
support for itwhich he promised to do. When he
later defended his views in his most famous work,
Dialogue Concerning the Two Chief World Systems,
published in 1632, he was tried by the
Inquisition, found "vehemently suspect of
heresy", forced to recant, and spent the rest of
his life under house arrest.
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Newtons Laws
Newtons 1st Law A body at rest remains at rest,
and one moving in a straight line maintains a
constant speed and same direction unless it is
deflected by a net force. Newtons 2nd Law The
force applied mass of an object
acceleration F ma Newtons 3rd Law For every
action force ON an object, there is an equal but
opposite force BY the object .
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