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History of Astronomy


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  • We see the Sun, Moon, and stars rise along the eastern horizon, move across the sky, and set along the western horizon.
  • The stars form patterns (constellations) whose shapes do not change.
  • We see different constellations at different times of the year—Orion in January, Scorpius in August, for example.
  • The shape of the lit portion of the Moon changes during the month.
  • Cycles of the Moon, Sun, and stars are the basis for keeping time and our calendar.
    • The day is based on the Earth’s spin (rotation about its own axis).
    • The month is based on the Moon’s orbital motion around the Earth.
    • The year is based on the Earth’s orbital motion around the Sun.
  • These motions also lead to seasons and eclipses.
  • Astronomers of antiquity deduced the shape and size of the Earth.
  • Starting around a.d. 1500, scientists such as Copernicus, Galileo, Kepler, and Newton deduced laws to describe and explain planetary motion.








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