1. Part 1: Astronomy: How our understanding of
the universe has changed
• In the 2nd century Claudius Ptolemy devised an ‘earth centered’ or
geocentric astronomical model of the known planets and stars.
• His theories were a refinement of other Greek astronomers ideas of the solar
system. (Iowa State, 2001)
• 1542: Nicolaus Copernicus published his definitive work on a ‘sun
centered’ or heliocentric astronomical model.
• The orbits of the planets were equally spaced and mathematically measured.
(Weisstein 2007)
• Further observations of the stars and the planets expanded our
knowledge of our solar system and galaxy. (Riebeek, 2009)
2. Example 1: Earth Central. Ptolemy and the
Geocentric Universe
• Circa 140 C.E. Ptolemy, (Latin
name Claudius Ptolemaeus),
theorized that the Earth was the
center of the Universe.
(Academic)
• Each planet revolved around the
Earth on its own orbit, or
epicycle.
• The Ptolemic system was
accepted for 1,300 years.
Claudius Ptolemy (1475, Van Gent)
3. Example 2: Seeing the Light. Copernicus and
the Heliocentric System
• 1508 Nicolaus Copernicus began
developing his own celestial system: A
Heliocentric system. (Biography 2015)
• The Planets moved in a circular
pattern around the sun. The size of
each planet’s orbit depended on its
distance from the sun. (A controversial
claim at the time!)
• 1514, he distributed The Little
Commentary, which contained the
Seven Axioms.
• 1543, On the Revolutions is published.
(NM, 2015)
Nicolaus Copernicus (Artist unknown, Viola 2014)
4. Example 3: The Universe Comes into Focus.
Galileo Galilei and the Telescope
• Through the use of his telescope,
Galileo discovers the surface of the
moon is rough. (Disproving the
Aristotelian belief that the heavens
were perfect).
• Observes the orbits of the four moons
of Jupiter. Proving that orbiting
moons, would not be left behind if a
celestial body moved through space.
(A Ptolemaic argument).
• Saw the phases of Venus. This
observation provided further proof
that the sun was central to the system
and not the Earth. (Iowa State 2001)
Galileo Explaining Lunar Topography to Two Cardinals
Jean Leon Huens, 1857 (Awesome)
5. Part 2 Historical Event: The Publication of
Johannes Kepler’s Astronomia Nova and
Harmonices Mundi
• The first two laws of planetary motion were published in 1609 in
Prague.
• Continuing his work, Johannes Kepler discovered the third law of
planetary motion on May 15, 1618. One year later he published
Harmonices Mundi (NASA, 2013)
6. The World in the Year 1609
• May 20, William Shakespeare’s
Sonnets published in
London(Historyorb, 2015)
• Aug. 25, Galileo demonstrates his first
telescope to the Venetian lawmakers
(Historyorb, 2015)
• Sept. 4, Henry Hudson becomes the
first European to discover the island of
Manhattan (Historyorb, 2015)
Shakespeare, (Tudor)
Hudson, (Historyorb, 2015)
7. Impact of Kepler’s Laws
• While Kepler’s work was not widely accepted at first, Galileo ignored his
writings, the work Kepler did in the fields of optics legitimized Galileo’s
own work with telescopes. (Science, 2015)
• Shortly after Kepler’s death, Pierre Gassendi and Jeremiah Horrocks,
observed the transits of Mercury in 1631 and Venus in 1639. Confirming
predictions Kepler had made about their orbits. (Science, 2015)
• It was the third law of planetary motion, not the proverbial apple, that led
Sir Isaac Newton to the law of gravity. (NASA, 2013)
8. Supporting Example 1
• Kepler’s analysis of Brahe’s observations of Mars led him to the
discovery of the first law: Planets move in ellipses with the Sun at one
focus. (NASA, 2013)
• The textbook, Epitome of Copernican Astronomy, was widely read for
twenty years after Kepler’s death. It contained his works on the
elliptical orbits of planets and many other discoveries made by Kepler.
(Science, 2015)
9. Supporting Example 2
• Prior to the discovery of the first law, Kepler observed what would
become the second law: The radius vector describes equal areas in
equal times. (NASA, 2013)
• All three of Kepler’s laws, from their inception to the present, have
retained their voracity. (Science, 2015)
