Nicolaus Copernicus

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Nicolaus Copernicus

• Born 1473 Torun, Poland
• Died 1543 Frauenburg, Poland

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Background and education

• Wealthy family
• Started education at University of Krakow
• moved to University of Bologna, Italy
• studied canon law
• moved to University of Padua, Italy
• studied medicine
• moved to University of Ferrara
• studied canon law - doctorate 1503

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Career

• Taught mathematics in Rome
• became canon at the University of Frauenburg
  this position supported his astronomical studies
• these date from Bologna
• roomed with an astronomer, Novara, who was the
  official astrologer for the city
• exposed to criticism of astrology and Ptolemy

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Background

• At this time - mathematics, astronomy and
  astrology were intimately associated
• problems with Ptolemy were that the order of the
  planets was indeterminate (Venus and Mercury)
• Structure of the zodiac was in question
• Copernicus tried other ways of arranging things

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Heliocentric system

• Fixed Sun at center of circular orbits for all
  the planets - including Earth
• All planets move at constant velocity along these
  circular orbits
• order of things was Mercury, Venus, Earth, Mars,
  Jupiter, Saturn
• Earth was just another planet

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Successes

• Explained the difference between the inferior and
  superior planets
• allowed the determination of the period for each
  planet
• allowed the determination of the distance of each
  planet from the Sun

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Results

• . Period Distance
• Mercury 88 days 0.39 AU
• Venus 7.5 mo. 0.72
• Earth 1 year 1
• Mars 2yrs 2mo 1.6
• Jupiter 11.9 yrs. 5.2
• Saturn 29.6 yrs. 9.5

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Results cont.

• In other words, the distance and period give the
  same order of the planets in the solar system
• simple explanation of retrograde motion - see the
  website following
• http//csep10.phys.utk.edu/astr161/lect/
  retrograde/copernican.html

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Remaining errors

• Circular orbits
• Constant velocity

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Publications

• 1503 wrote the Little Commentary but did not
  publish it.
• Visited by Georg Rheticus, mathematician, who was
  impressed by the heliocentric view
• Urged Copernicus to publish the book, undertook
  to do this
• No unpleasant response to this

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Role of Osiander

• This encouraged Copernicus to publish a larger
  work On the revolutions of the heavenly spheres
• Rheticus moves and cannot proceed with the new
  book
• Along comes Andreas Osiander, experienced with
  publishing technical books

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Osiander

• Takes on the task of publishing De
  Revolutionibus
• inserts a letter to the reader before the text
  saying that a) ideas presented did not represent
  truth, b) it was impossible to know the causes of
  heavenly phenomena
• book appears in 1543 just as Copernicus dies

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Major Conflict

• Geocentric versus heliocentric
• Extremely different views of the world
• But no clear way to decide which is true
• Needed more accurate observations of the planets
• Also needed improvements in Copernican view

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Interplay of theory and obs.

• Theory due to Copernicus
• Better (more accurate) observations need new
  observing tools
• Along came Tycho Brahe
• More accurate observations spur improvements in
  the theory
• Along come Kepler and Newton

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Old technology

• Hand held instruments
• made of wood
• small and non-standard instruments

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Astronomical and civil uses
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Brahe

• Danish nobility, wealthy, fascinated by astronomy
  (a precursor of Percival Lowell)
• interested also in alchemy
• lost part of his nose in a duel - gold
  replacement
• was given an island by the Danish king, Hven,
  near Copenhagen for an observatory

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Brahe

• He represents a new kind of scientist, a
  professional who did big science
• 1546-1601
• A transitional figure - between the apex of naked
  eye observations and the telescope (1608)

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Astronomical observations

• Observed the nova of 1572 - supposed to be a
  terrestrial phenomenon
• Brahe showed the nova was far away (parallax)
• Aristotle said it (nova) could not exist

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Astronomical observations

• Jupiter passes Saturn
• predictions were off by days to months
• Comet of 1577
• Aristotle said comets were terrestrial phenomena
  (in the atmosphere)
• Brahe showed that the comet was placed among the
  planets (parallax)

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Island of Hven
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www.hven.com/EUBORG.htmlwww.hven.com/ELKRKART.htm
l

• .

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Brahes observatory on the island of Hven as it
is today.
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View of scale on the great mural quadrant
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Brahes improvements

• Metal instruments
• fixed and therefore more stable
• large and therefore more accurate
• built a complete laboratory with printing shop,
  fabrication shops, assistants
• continuous observations (vital)
• corrected for refraction
• also proposed a cosmological theory

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Observations

• Normally, observations of a planet were only made
  at a few positions in its orbit
• Brahe had observations made continuously each
  clear night

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Tychonic system
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Brahes weaknesses

• Strong on observation
• weak on mathematics and theory
• enlisted the help of Kepler in 1600 at Prague
• at his death (1601), Brahe left his observations
  to Kepler
• Kepler published the best planetary positions
  (Rudolphine tables)

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Johannes Kepler

• Born 1571
• Died 1630
• he was convinced that the universe was designed
  according to geometrical principles (God was a
  geometer)
• trained as a mathematician
• imperial mathematician to Rudolf II

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Challenge

• Calculated the positions of the planets and
  compared with Brahes observation
• Worst agreement was for Mars
• He spent 4 years trying to explain the orbit of
  Mars

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Geometry aspect

• Kepler asked the question why are there only 6
  planets?
• Answer there are 5 platonic solids
• cube, octahedron, tetrahedron, dodecahedron, and
  icosahedron
• he used these solids to position the planets
  about the sun

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Platonic solids

• Cube - 6 faces -- earth
• tetrahedron - 4 faces -- fire
• octahedron - 8 faces -- air
• dodecahedron - 12 faces -- aether
• icosahedron - 20 faces --water

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Cube
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Tetrahedron
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Octahedron
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Dodecahedron
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Icosahedron
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Scheme

• Pick a solid (for example, the cube)
• start with a large sphere, solid inside touching
  the sphere
• place another sphere inside the solid so that the
  sphere touches the solid
• the planet moves in a circular orbit defined by
  the sphere
• then, place another solid inside the sphere so
  that its corners touch the sphere

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Something new

• Kepler thought that the sun had an influence on
  the planets (he didnt know about gravity)
• Problem action at a distance
• William Gilbert publishes a book on magnetism
• Kepler sees how this could couple the planets
  with the sun
• first physical explanation

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First law

• Using the observations of Brahe, Kepler decides
  that the planets move in elliptical orbits
• ellipse is a distorted circle

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• The Sun is at one of the foci
• therefore, the planet is closer to the Sun during
  part of the orbit
• and further away at other times

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Second law

• How did the planets velocity vary with distance
  from the planet?
• Three ways to do this
• velocity varies as 1/distance
• equal areas in equal time
• uniform velocity as viewed from the empty focus

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Equal area
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Second law cont.

• Kepler could not determine which was correct
• the observations were not good enough
• the problem remained until Newton

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http//csep10.phys.utk.edu/ astr161/lect/history/k
epler.html
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Third law
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Third Law
Earth distance 1 AU period 1
year Jupiterdistance 5.2 AU period 11.85
years
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Final test

• Calculate the positions of the planets and
  compare with observations
• these were the Rudolphine tables
• 30 times more accurate than the predictions of
  Copernicus

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Curiosity

• Planets do not follow elliptical orbits
• this is due to the gravitational attractions of
  each planets for all the others
• the observations of Brahe were not good enough to
  show this
• otherwise Kepler might have been misled

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Music of the spheres the belief that the planets
as they moved about the Sun generated music which
could not be heard but could be understood
intellectually
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Problems

• There still remained resistance to Copernicus
• largely theological
• what was needed was someone of stature who could
  sell the idea - Galileo