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The Earth

The Earth. Who discovered Earths shape and size?. Who was the first person to state the Earth was round? Pythagoras (Greek Scientist) lived ~ 500 BC. First person to propose that all celestial bodies are spherical. (also found Pythagorean theorem)

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The Earth

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  1. The Earth

  2. Who discovered Earths shape and size? Who was the first person to state the Earth was round? Pythagoras (Greek Scientist) lived ~ 500 BC. First person to propose that all celestial bodies are spherical. (also found Pythagorean theorem) Who was the first person to give scientific evidence that the Earth was round? Aristotle (Greek Scientist) lived ~ 300 BC. First person to show scientifically that the earth could not be flat. He noted travelers going south see southern constellations rise higher above the horizon. Who was first person to measure the size of the Earth? Eratosthenes (Greek Scientist) Lived ~ 200 BC. First person to attempt to measure the Earth. He used shadows cast from the sun to determine an estimated size of the Earth. It was the Ancient Greeks who discovered the size and shape of the Earth.

  3. Evidence that the Earth is round The first evidence that the Earth is round is sunrise and sunset. Every day the sun rises from the horizon and drops back below it.

  4. Evidence that the Earth is round When a ship appears over the horizon it starts from the top and slowly rises, this is only due to the round shape. How does a ship appear over the horizon?

  5. Evidence that the Earth is round • During a Lunar Eclipse the Earth cast a round shadow over the moon (not the same as moon phases)

  6. Evidence that the Earth is round • The altitude of stars (especially Polaris) changes with your latitude. • Polaris is at 90 deg at the North pole. • It is at 0 deg at the equator. • It changes with your latitude. • Whatever angle Polaris is in the sky IS YOUR LATITUDE

  7. Eratosthenes method

  8. How was the Earth first measured • Eratosthenes knew that in Syene Egypt, a deep well cast no shadow over the water on the first day of summer (showing the sun was directly overhead) • He also knew a tower in Alexandria Egypt cast a shadow on that same day of 7° (1/50th of a circle) • By finding the distance between Syene and Alexandria and multiplying by 50 he found Earths size. • Unfortunately since he used the Unit of Stadia and we no longer know what a Stadia is, we do not know how accurate he was. However the method does work. It is believed he was within a 10 % error.

  9. Earths True size and shape • What shape does the Earth appear to be? • The Earth “appears” to be a perfect sphere. • Is the Earth a perfect sphere? • Earths Measurements • N/S, Pole to Pole = 7901 mi • E/W, through equator = 7926 mi • The Earth is an Oblate Spheroid • It is slightly flattened on top and bulging at the sides • due to its rotation.

  10. What did Columbus do • Columbus made a Mistake. • By 1492 AD people already knew • the Earth was round. • There was no debate about the shape of the Earth before his trip. • The debate was about the size of the Earth which Columbus thought was much smaller. (he was wrong) • Just before accidentally hitting the Americas the crew was all but out of food and mutinies were a foot. • If not for luck, Columbus and his men would have died. • The story of 1492 was made up in 1828 by Washington Irving in a book about Columbus’ voyage. Over time people mistakenly took as fact.

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