Observing the Solar System

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Observing the Solar System

• Chapter 23 Section 1

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Sun around the Earth?

• Stars dont appear to move, planets and the sun
  do.
• Night and day caused by sun going around Earth.
• Moon orbits Earth, everything must also.

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Ptolemy

• Greek astronomer (140 BCE)
• Geocentric theory of solar system

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Geocentric Theory
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Earth around the sun?

• Aristarchus (270 BCE)
• Copernicus (1510 CE)
• Heliocentric theory of solar system

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Heliocentric Theory
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Galileo Galilei (1610 CE)

• Uses telescope to support heliocentric theory
• Jupiters moons dont orbit Earth
• Venus has phases like our moon
• Parallax of stars (Aristotle said there was none)

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Galileo Galilei
Put on trial by the Inquisition for supporting
heliocentric theory (1633 CE) result was
Copernicus book banned
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Tycho Brahe (1570 CE)

• Mapped the positions of stars and planets for 20
  years

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Johannes Kepler (1600 CE)

• Discovered elliptical orbit of planets

Copernicus Kepler
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Johannes Kepler (1600 CE)

• Explained retrograde motion of planets better

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Johannes Kepler (1600 CE)

• Explained retrograde motion of planets better

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Sir Isaac Newton (1665 CE)

• Gravity was still an unexplained concept
• Newton discovers that gravity and inertia keep
  things in orbit.
• Gravity attracts all things in universe and
  increases as size (mass) of object increases
• Inertia is objects want to move in a straight
  line
• Sun much bigger than Earth so no way it would go
  around Earth.

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How fast is the Earth revolving?

• Speed distance / time
• Time it takes Earth to revolve once?
• Right365.25 days, which is 31,557,600 seconds
• Average distance from Earth to sun is 150 million
  kilometers (90 million miles)this is the radius
  of its nearly circular orbit
• Circumference of circular orbit is (2)(3.14) r
• Distance of Earths revolution is
  (2)(3.14)(150,000,000)
• So, the speed would be 9.42 x 108 kilometers /
  3.16 x 107 seconds, which equals
• 29.8 Km/sec (here to Camarillo) or 1,788 Km/min
  (here to Seattle) or 107,280 Km/hr (around Earth
  2.5 times)