Galileo and his telescope

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Galileo and his telescope

• Dr Bryce

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Class notices

• Homework 2 due today

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Galileo Galilei 1564-1642
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Galileo overcame major objections to Copernican
view. Three key objections rooted in Aristotelian
view were

• Earth could not be moving because objects in air
  would be left behind.
• Non-circular orbits are not perfect as heavens
  should be.
• If Earth were really orbiting Sun,wed detect
  stellar parallax.

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In Pisa

• According to legend he dropped balls of different
  masses from the tower to show that they fell at
  the same rate.
• In reality his experiment used rolling balls to
  show that a moving object remains in motion
  unless a force acts to stop it.

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The telescope

• Galileo did not invent the telescope.
• He did build his own
• And use it in a logical and systematic way
• He made the first recorded observations of many
  celestial objects.

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One of his first targets

• Was the Sun
• Not recommended, Galileo lost his own sight
• Sunspots, the Sun is rotating and not a perfect
  sphere!

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The Moon through a telescope
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Galileo and Stars

• The ancient world had a heaven that did not
  change but observations such as a supernova and
  comet during Tychos lifetime were contradictory
  to that.
• Galileo observed that the Milky Way was made up
  of many stars rather than creamy nougat and
  caramel.
• Stars were further away hence no stellar
  parallax measurements

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Galileo and Jupiter

• Observed stars close to Jupiter.
• Overtime the stars positions changed.
• Are in fact Moons.
• How can Earth have the Universe orbit around it
  when there are objects orbiting Jupiter

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Galilean Moons

• Io
• Europa
• Ganymede
• Callisto
• And the Great Spot was first recorded by Galileo

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Saturn
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Saturn and Galileo

• 1610 large Moons on both sides
• 1612 the objects have disappeared, Earth was
  crossing the same plane as the rings
• 1616 Two half ellipses
• 1655 Huygens proposes that the objects are rings
• 1883 First photograph of Saturns rings

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Venus

• Venus goes through phases
• Which only makes sense if it is orbiting the Sun
  and not the Earth
• Was the observation that the Copernican
  revolution needed!
• Landed Galileo in hot water.

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Scientific Method
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Science
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Bad Science

• Disregards observations at whim
• Disregards known laws at whim
• Not testable
• See Astrology
• See www.badastronomy.com for a lighthearted look
  at mistakes in movies, television and popular
  culture.