anthony morris
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Earth 🜨

  • 13,000 kilometers in diameter
  • The Moon is the nearest astronomical neighbour Earth and Moon, drawn to scale
  • The Sun is about 150 million kilometers away
  • Axis of rotation is tilted 23.5˚
    • This is why the Sun is visible for less time in the winter and more time in the summer (in the northern hemisphere)

Calculating Earth's Size in Ancient times

How the Earth's size was calculated

  • In Syene, the Sun was straight overhead (no shadows created) but in Alexandria had shadows with 7˚
  • This means at Alexandria, Earth's surfaced has curved by 7˚ (1/50 of a full circle)
  • The distance between the two cities must then be 1/50 the Earth's circumference, so we can measure that

Space Astronomy