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Ch.29--Astronomy

Ch.29--Astronomy. The Astronomical Unit. A convenient unit of distance measurement within the solar system. Miles / kilometers are too small, and light years are too large. One astronomical unit (AU) is defined as the average distance between the earth and the sun.

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Ch.29--Astronomy

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  1. Ch.29--Astronomy

  2. The Astronomical Unit • A convenient unit of distance measurement within the solar system. Miles / kilometers are too small, and light years are too large. • One astronomical unit (AU) is defined as the average distance between the earth and the sun. • Pluto’s distance from the sun is 39.72 AU’s. This equates to 5.5 light-hours.

  3. Age of the Solar System • Very accurate radioactive dating methods of lunar samples, terrestrial samples, and meteorites indicate that the solar system is approximately 4.6 billion years old.

  4. Earth’s Evolution • As Earth formed from the solar nebula, it heated and melted. • Differentiation took place, with heavier elements sinking to the center. • The least dense materials (gases) were burped out to form an atmosphere. This early primitive atmosphere was probably similar to present-day volcanic gases.

  5. UV light from the sun would have kept the surface sterile, until oxygen was released and formed a protective ozone layer in the upper atmosphere.

  6. Asteroid Impact Effects • Have caused extensive cratering on the Moon, Mercury and other bodies in the solar system. • Most craters on Earth have been obliterated by active recycling of the planet’s surface. • Some large impacts have had a dramatic effect on life on Earth, resulting in mass extinctions.

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