Views of the Universe

1
Views of the Universe
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Views of the Solar System
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What Galaxy are We In

• We are located in the Milky Way Galaxy which is
  one of hundreds of billions of galaxies.

4
Our Solar System

• The sun is one of at least 200 billion stars in
  our galaxy alone. If the Milky Way is one of
  billions of galaxies then imagine how many solar
  systems are out there!

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Views of Our Universe

• Aristotle (who lived about 384 BCE) held that the
  Earth is the center of the universe.
• This idea was held to be true for almost 2,000
  years.
• Who was the first person to document a
  heliocentric view of the universe?
• http//www.astro.utoronto.ca/zhu/ast210/geocentri
  c.html

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The Other Greek

• If you said Copernicus you are wrong!
• Aristarchus of Samos 310-230 BCE proposed a
  heliocentric universe.
• Copernicus used Aristarchus ideas to create his
  heliocentric model.
• http//www.astro.utoronto.ca/zhu/ast210/helicentr
  ic.html

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Why We Care

• Several problems were facing astronomers trying
  to use the Ptolemaic system
• The tables used to predict events such as
  eclipses were not accurate.
• Portuguese and Spanish explorers (like Columbus)
  who were traveling to the Far East and America,
  needed to navigate by the stars because they
  would be out of sight of land for weeks.

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The Calendar

• The calendar, instituted by Julius Caesar in 44
  BCE was no longer accurate.
• The Spring Equinox, which at the time of the
  Council of Nicea (325 CE) had fallen on the 21st
  of March, had now slipped to the 11th.
• The date for Easter is determined by the Spring
  Equinox. The other holidays are determined from
  Easter. So the entire calendar was messed up!

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Why Was Aristarchus Model Ignored

• If the Earth spins on an axis why don't objects
  fly off the spinning Earth?
• If the Earth is in motion around the sun, why
  doesnt it leave behind the birds flying in the
  air?

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Parallax

• If the Earth is actually on an orbit around the
  sun, why isn't a parallax effect observed?

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Parallax Explained

• Stars should appear to change their position with
  respect to the other background stars as the
  Earth moves about its orbit, because of viewing
  them from a different perspective.

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Copernicus Controversy--Not

• Copernicus was a leader in the Church.
• He dedicated his book, "On the Revolutions of the
  Celestial Orbs" to Pope Paul III.
• The book was published the year of his death and
  caused little controversy.

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The Great Controversy

• Galileo and Kepler changed everything.

14

• Galileo Heliocentrichttp//www.teachersdomain.org
  /resources/ess05/sci/ess/eiu/galileosys/index.html
  
• Why We Don't Feel the Earth Move
• http//www.teachersdomain.org/resources/phy03/sci
  /phys/mfw/galthought/index.html