By Ken Journigan Independence High Astronomy

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By Ken JourniganIndependence High Astronomy

• The History of Astronomy

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Astronomical History

• A very complete story of astronomy is told in
  its history. The men and women of astronomical
  history are synonymous with the historical
  evolution of this observational science.

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Universal Models

• The
• Geocentric Model Supporters

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The Geocentric Model of the Universe

• With one mere exception (to be named later),
  ancient astronomers placed the Earth at the
  center of the known Universe. This Universal
  Model was known as the Geocentric Model. Geo
  meaning Earth and centric meaning centered.

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Aristotle (384 BC March 7, 322 BC)

• Aristotle was an ancient Greek philosopher, a
  student of Plato and teacher of Alexander the
  Great. Aristotle had a strong influence, and his
  teachings carried great weight. He promoted the
  geocentric model.
• According to Aristotle the cosmos were composed
  of five fundamental properties
• Earth
• Air
• Water
• Fire
• The spherical shells of
• heavenly bodies with Earth
• at the center

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Aristotle

• Aristotle believed that everything in the
  regions outside the Earth was perfect and
  eternally unchanging. All objects in the heavens
  were supposed to be perfect circles, except for
  stars, which were featureless points of light.

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Aristotle

• Aristotle concluded that the Earth was round and
  not flat as some at the time believed. He based
  this on his observation of lunar ellipses where a
  portion of the Earths shadow falls on the moon.

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Aristotle

• Aristotles beliefs about the geocentric model
  of the universe would pervade astronomy to such
  an extent, that they would not be challenged for
  another 1500 years.
• Plato and Aristotle

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The Greek Astronomer Hipparchus

• Hipparcus (c. 190 BCE--c. 120 BCE) was born in
  Nicaea, a city in what is now Turkey. In the year
  135 BCE, he was stargazing and saw a bright point
  of light he didn't recognize.
• This star appeared in
• the constellation Scorpio.
• It turned out to be a
• supernova. This disproved
• Aristotles idea of the
• perfect, unchanging Universe

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Warm Up

• What is a geocentric model of the universe?
• What did Aristotle say were the 5 natural
  elements?
• What did Aristotle say about how the Universe
  changed?
• What are crystal spheres?
• Name three innovative (new) things that
  Hipparchus did!
• According to Hipparchus system to classify stars,
  what is the brightest star?
• According to Hipparchus system to classify stars,
  what is the dimmest star?
• What is procession?

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The Greek Astronomer Hipparchus

• Developed the first catalog of stars
• Developed a magnitude scale
• where 1 represented the brightest
• stars and 6 represented the
• dimmest stars.
• Determined the precession
• of Earth based on records
• from the past and compared
• it to his own observations

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The Greek Astronomer Hipparchus

• Hipparcus cataloged the locations and brightness
  of over 850 stars. In addition, he calculated
  the length of the year to within seconds of its
  actual value and developed a system to predict
  eclipses to within hours.

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Hipparchus Being Typically Greek
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The Greek Astronomer Hipparchus

• Hipparchus had a problem making his star chart.
  It was easy enough to map the surface of the
  Earth, because the Earth has landmarks rivers,
  mountains, cities--places of known location, to
  which other places can be compared. The sky,
  however, has no landmarks, just the stars
  themselves. Hipparchus decided to invent
  "landmarks" of his own. He picked one point in
  the sky and drew imaginary lines radiating out
  from it, like the spokes of a wheel. Then he drew
  circles around this central point which grew
  larger and larger.

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The Greek Astronomer Hipparchus

• This made a grid around the sky, on which
  Hipparchus could locate any star he wanted. This
  idea soon improved Earthly map-making as well
  the modern lines of longitude and latitude come
  directly from Hipparchus's method of mapping the
  sky.
• Instead of locating stars on the "celestial
  sphere" (the entire
• area visible around the Earth),
• later map-makers drew
• gridlines on their charts
• of the Earth's sphere.

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Eratosthenes and Size of the Earth

• About 200 BC, Eratosthenes used Aristotle's ideas
  to calculate the size of the Earth. On a certain
  day of the year, observers at Syene, Egypt saw
  the sun directly overhead. Observers at other
  locations (Alexandria, Egypt) saw the sun at an
  angle on that day. The angular displacement was
  measured.
• Using simple geometry, he
• calculated the circumference
• and the radius of the Earth.
• The result was within 1 percent
• accuracy of the figure known today.

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Ptolemy

• When I trace at my pleasure the windings to
  and fro of the heavenly bodies, I no longer touch
  the earth with my feet I stand in the presence
  of Zeus himself and take my fill of ambrosia,
  food of the gods.Quoted in C B Boyer, A History
  of Mathematics (New York 1968)

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Ptolemy

• Ptolemys full Latin name was Claudius
  Ptolemaeus (fl. AD 127-145, Alexandria), He was
  an ancient astronomer, geographer, and
  mathematician who considered the Earth the center
  of the universe
• (the "Ptolemaic system").
• Virtually nothing
• is known about his life.

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Ptolemy

• Claudius Ptolemy lived in Rome around 100 AD.
  His model of the solar system and heavenly sphere
  was a refinement of previous models developed by
  Greek astronomers. Ptolemys major contribution,
  however, was that his model could so accurately
  explain the motions of heavenly bodies, it became
  the model for understanding the structure of the
  solar system. Nearly all the early models,
  including Ptolemys version of the solar system,
  assumed that the Earth was the center of not only
  the solar system, but the entire universe.

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The Ptolemaic Model

• The Ptolemaic model accounted for the apparent
  motions of the planets in a very direct way, by
  assuming that each planet moved on a small sphere
  or circle, called an epicycle, that moved on a
  larger sphere or circle, called a deferent. The
  stars, it was assumed, moved on a celestial
  sphere around the outside of the planetary
  spheres.

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The Epicycle

• http//physics.syr.edu/courses/java/demos/kennett/
  Epicycle/Epicycle.html
• The idea of the epicycle was incorporating into
  Ptolemys universal model in order to explain
  retrograde motion

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Prograde Versus Retrograde Motion

• Prograde Motion The regular west to east
  migration of celestial bodies across the sky.
• Retrograde Motion The irregular and periodic
  transit of planets across the sky from east to
  west.

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Universal Models

• The
• Heliocentric Model Supporters

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The Heliocentric Model

• Heliocentric (sun-centered) model
• More accurately accounted for all observations
  of the movement of the sun and the moon, and the
  planets, and the stars
• were good predictors of future positions of
  celestial bodies models were verifiable
• simplicity (Occam's Razor or the Principle of
  Parsimony) - as few assumptions or rules as
  possible no contradictions.

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Heliocentric Model

• Aristarchus of Samos, a Greek about 310-230 BC,
  had a heliocentric model. He proposed that all of
  the planets, including Earth revolved around the
  Sun, and that the Earth rotates on its axis once
  a day. His ideas did not gain widespread
  acceptance during his lifetime.

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Aristarchus of Samos

• Aristarchus was the first person to give the
  solar system scale.

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Nicholaus Copernicus
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Nicholaus Copernicus and the Revival of the
Heliocentric Universe.

• Nicholaus Copernicus was a Polish cleric
  (1473-1543) that lived around 1500. He was
  dissatisfied with the complexity of the
  geocentric model. His beliefs would ultimately
  get him in trouble with the Church.

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Nicholaus Copernicus and the Revival of the
Heliocentric Universe.

• His ideas included
• Sun is at the center of the universe, motionless
  stars are motionless around the edge
• Planets all revolve around the sun (6 total
  including Earth)
• Moon revolves around Earth
• Earth rotates on axis causing apparent daily
  motion of the heavens
• Earth revolves around sun causing sun's annual
  movements
• Retrograde motion of planets is due to relative
  planetary motions
• Planetary orbits are perfect circles

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Nicholaus Copernicus and the Revival of the
Heliocentric Universe.

• Copernicus was the first to accurately determine
  the relative distances of the planets from the
  sun.

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Planetary Distances According to Copernicus

• Planet Copernican Distance Real Distance
• Mercury 0.38 AU 0.39 AU
• Venus 0.75 AU 0.72 AU
• Earth 1.00 AU 1.00 AU
• Mars 1.52 AU 1.52 AU
• Jupiter 5.22 AU 5.20 AU
• Saturn 9.17 AU 9.54 AU
• Copernican views marked the beginning of the
  modern era of astronomy.

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Tycho Brahe
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Tycho Brahe

• Tycho Brahe was born in Denmark in 1546 to a
  noble family. He was the nephew of Jorges Brahe,
  a sailor who gave his life in an effort to save
  the life of King Fredrik II of Denmark. Tycho
  Brahe
• benefited greatly from King
• Fredrik's generous support.
• Brahe received an island
• called Hven from the king.
• He turned this island into
• his own little country.

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Tycho Brahe

• Brahe built a castle on Hven and named
• it Uraniborg after Urania, the goddess of the
  sky. He also built an observatory on the island.
  For over 20 years, Brahe used the island as his
  base from which to make astronomical
  observations. In 1597, Tycho Brahe lost the
  Danish king's support, so he went to Wandsbech in
  Germany. He eventually settled in Prague where he
  continued his astronomical observations. Prague
  was the capital of the Catholic Church.

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Tycho Brahe

• Over a 20 year period of time, Tycho Brahe made
  consistent observations which supported the
  heliocentric theory proposed earlier by
  Copernicus. These observations were made using
  only a compass and
• a sextant.
• Brahe catalogued
• over 1000 stars.

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Johannes Keplar (12/1571-11/1630)
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Johannes Keplar Keplar

• My aim is to say that the machinery of the
  heavens is not like a divine animal but like a
  clock (and anyone who believes a clock has a soul
  gives the work the honor due to its maker) and
  that in it almost all the variety of motions is
  from one very simple magnetic force acting on
  bodies, as in the clock all motions are from a
  very simple weight.

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Johannes Keplar (12/1571-11/1630)

• Born in present-day Germany.
• Pursued priesthood, but
• finally decided to teach math.
• Learned of the Copernican
• model in advanced astronomy.
• Excommunicated in 1612.
• Coined the term satellite.

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Johannes Keplar Keplar

• Sent copies of some of his work to Tycho Brahe.
• Tycho Brahe wrote to Keplers teacher that he
  needed a mathematical assistant and hired Kepler.
• Completed his work on the orbit of Mars in 1605.
• Created infinitesimal calculus after watching
  tradesmen measure the volume of wine in barrels
  at a wedding.

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Kepler's Laws

• The orbit of each planet is an ellipse with the
  sun at one focus.
• The square of the period of revolution of a
  planet about the sun is proportional to the cube
  of the semi-major axis of the planets elliptical
  orbit.
• These laws are illustrated in the following
  diagram

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Kepler's First Law

• The orbit of each planet is an ellipse with the
  sun at one focus.

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Kepler's Second Law

• The line segment joining a planet to the sun
  sweeps out equal areas in equal time intervals.

http//www.walter-fendt.de/ph11e/keplerlaw2.htm
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Kepler's Third Law

• The square of the period of revolution of a
  planet about the sun is proportional to the cube
  of the semi-major axis of the planets elliptical
  orbit.

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Kepler's Third Law (contd)

• The square of the period of revolution of a
  planet about the sun is proportional to the cube
  of the semi-major axis of the planets elliptical
  orbit. P2 A3 where P is the orbital period
  (AU) and A is the area inscribed by the
  semi-major axis.

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Kepler's Laws

• Kepler provided us with a tool, accurate even by
  todays standards, to understand the mechanical
  universe and the orbital nature of the planets.
• The only remaining question, was why did the
  planets move the way they did?
• The answer to that question could be provided by
  only one man arguably the greatest scientist the
  world has ever seen.
• Sir Isaac Newton

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Warm Up

• 1.) State Johanne Keplers 3 Laws of Planetary
• Motion.
• 2.) Explain what each one means (so that even I
  can understand it). Define any variables that
  you might use!
• 3.) Observations of what planet lead to Keplers
  understanding of planetary motion?
• 4.) How do you form an ellipse? What are foci?
  What is a semi-major axis?

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But first, what about Galileo?

• Galileo Galilei
• 1564 - 1642

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Galileo Galilei

• Spent his childhood in Pisa, Italy
• Family wanted him to be a
• doctor.
• Left the University of Pisa in
• 1585 without his degree.
• Saw Keplers supernova in
• 1604 while teaching math at
• the University at Padua (Venice).

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Galileo Galilei

• Formulated Laws of Motion from observations and
  experimentation with pendulums and inclined
  planes.
• Learned of the perspicillum
• in 1609.
• Created his own telescope and
• improved on the design by teaching
• himself how to grind lenses .

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Insert The Early Telescope

• tele 'far' and skopein 'to look or see'
• Invented by Dutch spectacle maker
• Hans Lippershey in the 1590s.
• Lippershey is the only person to
• apply for a patent for the
• telescope.
• First paper published about use of
• telescope for observation was by
• Englishman Thomas Harriott

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Galileo Galilei

• Sold the rights to the telescope to
• the Venetian Senate
• for a better position.
• Laughed because he
• did not own them.
• Began nighttime
• observations in 1609.

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Galileo Galilei

• His observations included
• Mountains on the Moon.
• The Galilean moons of Jupiter.
• The phases of Venus.
• Saturn and its rings (though he did
• not understand why they periodically
• disappeared).
• Sunspots.

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Galileo Galilei

• Convicted of heresy, Galileo was placed under
  house arrest for the remainder of his life, a
  gentle punishment for any individual convicted
  during the Inquisition.
• On 31 October 1992, 350 years after Galileo's
  death, Pope John Paul II gave an address on
  behalf of the Catholic Church in which he
  admitted that errors had been made by the
  theological advisors in the case of Galileo. The
  Church however never admitted that they were
  wrong in declaring Galileo a heretic!

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Sir Isaac Newton (1642-1727)
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Sir Isaac Newton

• Born in Woolsthorpe, Lincolnshire, England on
  Christmas Day. He was quite premature and not
  expected to live. (His mother said that when he
  was an infant, that she could fit him inside a
  one quart pot).
• Newtons father died a few
• months before his birth.

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Sir Isaac Newton

• His mother remarried to a wealthy clergyman, left
  home, leaving Isaac to be raised by his
  grandmother
• Eight years later, she returned, with three more
  children and another dead husband. (Shes not
  having much luck with her husbands, is she?).
• Two years later, Newton went away to Grammar
  School in Grantham, where he lodged with the
  local apothecary, and learned his fascinated of
  chemicals.

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Sir Isaac Newton

• In 1661, his uncle convinced his mother to send
  Newton to Trinity College, Cambridge.
• He supported himself by working in a tavern and
  cleaning for other faculty and wealthy students.
• In the summer of 1665, the Black Plague came to
  Cambridge and Trinity College closed its doors.
• Newton returned home to Woolsthorpe.

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Sir Isaac Newton

• The two years between leaving and returning to
  Cambridge, mark Newtons most remarkable and
  productive years.
• During this time he formulated his ideas on
  moving bodies, gravity and light.
• He also invented integral, differential and
• infinite series calculus during this time.
• In 1667, began his work in alchemy (explain).

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Sir Isaac Newton

• Newton disliked publishing his work and usually
  did so in response to other published articles.
• He was frequently embroiled in debates over the
  originality of his work.
• He was haphazard regarding the care of his work
  and frequently
• lost and misplaced things.

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Sir Isaac Newton

• Newtons first major publication regarded his
  invention, design and construction of the first
  reflecting (or Newtonian) telescope.
• Eliminated chromatic aberration.

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Sir Isaac Newton

• Newton elected to the Royal Society.
• Through the 1670, Newton became obsessed with
  theology and alchemy. He deeply desired to
  understand the nature of matter. He also tried
  to calculate to age of the Earth using biblical
  texts. To do this he taught himself Hebrew.

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Sir Isaac Newton

• In 1684, three members of the Royal Society, Sir
  Christopher Wren, Robert Hooke and Edmond Halley,
  argued as to whether the elliptical orbits of the
  planets could result from a gravitational force
  towards the sun proportional to the inverse
  square of the distance. Halley writes
• Mr. Hook said he had had it, but that he would
  conceal it for some time so that others, triing
  and failing might know how to value it, when he
  should make it publick.
• (Yea, right!!! What a load!)

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Sir Isaac Newton and Edmond Halley

• Having heard the rumor that Newton already had
  the solution they sought, Edmond Halley (namesake
  of the comet) visited the mathematician.
• Newton replied that he had the proof from fours
  years earlier, but sought in vain to find it.
• Newton devoted the next three months to
  reproducing the proof.

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Sir Isaac Newton

• Published the Principia in 1686, widely regarded
  as the greatest scientific work ever published.
• Publication made Newton a very public figure
  which he quickly grew accustomed to.
• He was appointed Master of the Mint and moved
  from Cambridge to London. He was responsible for
  many improvements to currency to control
  shaving and counterfeiting (ridges, like
  quarters today.

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The Ideas of Isaac Newton

• The central topic of the Principia was
  gravitational force. Defined by Newton as
• Fg G (M1) (M2)/ r2 where (the inverse
  square law)
• Fg The force of gravity
• G The gravitational constant
• M1 The mass of body one
• M2 The mass of body two
• r the distance between the centers of the two
  bodies

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Sir Isaac Newton

• Orbital flight was explained by Newton in a
  though activity called the mountain cannon.
• Is seeks to show how an object may continually
  fall and still never his the ground of a round
  body.
• http//galileoandeinstein.physics.virginia.edu/mo
  re_stuff/Applets/newt/newtmtn.html

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Newtons First Law of Motion

• Newtons First Law of Motion states that
• F ma where
• F force
• m mass
• a acceleration

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Newtons Second Law of Motion

• Newtons Second Law of Motion is the Law of
  Inertia which states that
• A body in motion tends to stay in motion (in a
  straight line) and a body at rest tends to stay
  at rest, unless acted upon by some external
  force.
• Mass resists change and the natural state of
  matter is to be in motion!

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Newtons Third Law of Motion

• Newtons Third Law of Motion states
• For every action there is an equal, but
  opposite, reaction.
• Or, if I push you, then you push me and
• if you push me then I push you!

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Isaac Newton

• Creator of
• Reflecting telescope
• Laws of Motion
• Laws of Gravity
• Calculus
• Astrophysics
• Our understanding of the true nature of light
• (Not a bad resume, eh?)