Chapter 1 1'4: Modern Astronomy

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Chapter 11.4 Modern AstronomyChapter 2,
Gravity

• Dr. Michelle Arnold
• September 11, 2009

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1.4 Modern Astronomy

• 1650 A.D. - present

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Marked Advances ofthe Past 350 Yeard

• Isaac Newton (1642-1727 A.D.)
• Pioneered modern study of motion, optics and
  gravity
• Uranus discovered (1781)
• Neptune discovered due to irregularities in
  Uranus orbit
• Improved telescopes
• Discovery of galaxies about 80 years ago
• Man has visited the moon
• Unmanned probes have travelled our solar system

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Chapter 2Gravity
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Galileo and Inertia

• Galileo conducted experiments to investigate
  motion
• Inertia objects resist changes to their speed
• An object in motion stays in motion
• An object at rest stays at rest
• Incline plane experiment to show this
• All objects fall at the same rate on Earth

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Newtons Laws of Motion

• Newtons (Galileos) First Law An object will
  continue to move in a straight line with constant
  speed unless a force acts on it.
• Some force is acting on the planets
• Newtons Second Law F ma
• Force (F) a push or a pull
• Acceleration (a) a change in velocity, which
  can be a change in speed or direction
• Mass (m) the amount of matter in an object
• Measured in kilograms (kg)
• Does not change from one place to another (weight
  does)
• Acceleration is greater if the force is larger,
  or if the mass is smaller
• Newtons Third Law when one object exerts a
  force on a second object, the second object
  exerts the same size force in the opposite
  direction on the first object

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Gravity

• Newton did not discover gravity
• Newton made the connection between gravity
  causing objects to fall down on the Earth and
  causing objects to orbit other objects

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