Ancient Astronomy.pptx

Ancient Astronomy

1. Ancient Astronomy

2. ANCIENT ASTRONOMY The Greeks are very much noted for their major contributions in different fields. They were not only great philosophers but great scientists and mathematicians as well. It was in Greece that the Golden Age of early astronomy was centered. They used philosophical arguments to explain the natural events. They used basics of geometry and trigonometry in measuring sized and distances of the sun to the moon. Tuesday, February 2, 20XX Sample Footer Text 2

3. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclipse – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 3

4. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclise – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 4

5. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclise – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 5

6. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclise – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 6

7. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclise – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 7

8. ANCIENT ASTRONOMY Key terms: Oblate Spheroid – the shape of the Earth. It has bulging equator and squeezed poles. Solstice – either of the two times in the year: the summer solstice and winter solstice Eclise – an obscuring of the light from one celestial body by the passage of another one between it Heliocentrism – astronomical model in which the Earth and planets revolve around the sun Geocentrism – Earth is assumed to be the center of all Tuesday, February 2, 20XX Sample Footer Text 8

9. ANCIENT ASTRONOMY Around 500 BC, most Greeks believed that the Earth was round, not flat. It was Pythagoras and his pupils who were first to propose a spherical Earth. Anaxagoras – shadow of the Earth cast on the moon during lunar eclipse was circular 340 BC: Aristotle listed several arguments for a spherical earth such as positions of the North Star, shape of the moon and sun and disappearance of the ships when they sail over the horizon Tuesday, February 2, 20XX Sample Footer Text 9

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11. ANCIENT ASTRONOMY Tuesday, February 2, 20XX Sample Footer Text 11 NORTH STAR -was believed to be at fixed position in the sky, however when the Greeks traveled to places nearer the equator, like Egypt, they noticed that it is closer to the horizon

12. ANCIENT ASTRONOMY Tuesday, February 2, 20XX Sample Footer Text 12 Aristotle argued that if the Moon and the Sun were both spherical, then perhaps the Earth was the same

13. ANCIENT ASTRONOMY Tuesday, February 2, 20XX Sample Footer Text 13 Disappearing ships - If the Earth was flat, then a ship traveling away from an observer should become smaller until it disappeared.. But the Greeks observed that the ship became smaller and its hull disappeared first before the sail.

14. Size of the spherical Earth 14 ERATOSTHENES – gave the most accurate size during their time. Syene (Southern Egypt) and Alexandria : Vertical object shadow From his measurement: he computed the circumference of the Earth to be approx. 250,000 stadia, about 40,000 km

15. ANAXAGORAS Tuesday, February 2, 20XX Sample Footer Text 15 ANAXAGORAS – was able to explain what causes the phases of the moon. To him, the moon shone only by reflected sunlight. Since it is a sphere, only half of it illuminated at a time and it changes periodically.

16. Eudoxus 16 EUDOXUS – proposed a system of fixed spheres. He believed that the sun, moon and the five known planets and the stars were attached to these spheres which carried the heavenly bodies while they revolved around the stationary Earth.

17. ARISTOTLE 17 ARISTOTLE – was a student of Plato. For him, the earth is spherical in shape since it always casts a curved shadow when it eclipses the moon. He also believed that the Earth was the center of the universe

18. ARISTARCHUS 18 ARISTARCHUS – very first Greek to profess the heliocentric views “ helio ” – sun “centric”- centered

19. Eratosthenes 19 ERATOSTHENES – the first successful attempt to determine the size of the Earth was made by him by applying geometric principles. -he observed that at the noonday sun in two Egyptian cities that were almost opposite each other – Syene (Aswan) in South and Alexandria in the North. He assumed they were in the same longitude.

20. Hipparchus 20 HIPPARCHUS – is considered as the greatest of the early Greek astronomers who compared and observed the brightness of the 850 stars and arranged them into order of brightness or magnitude. -he also developed a method for predicting the times of lunar eclipses to within a few hours. -he also measure the length of the year to within the minutes of the modern value

21. CLAUDIUS PTOLEMY 21 CLAUDIUS PTOLEMY – believed that the Earth was the center of the universe. His Ptolemic model claimed the planets moved in a complicated system of circles

22. 22 PTOLEMIC SYSTEM

23. PTOLEMIC MOD EL 23 The sun, moon and other planets move in circular orbits around the Earth. However, if observed night after night, these planets move slightly eastward among the stars. RETROGRADE MOTION – planets moves in the opposite direction for some time, after which it resume its eastward motion

24. ARISTOTLE’S CONCLUSION 24 He lived in ancient Greece more than 300 yrs before the common era (BC). In those days, most people believed that many gods ruled the universe. He is regarded as the Father of Natural Science. His methods were basis for scientific method. He considered the position of the North Star He also observed that he could see the top of the sails first before the rest of the ship. (because of the earth’s curvature)

25. Thank You Tuesday, February 2, 20XX Sample Footer Text 25

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