Planets known in Ancient Times

Planets known in Ancient Times - Greeks knew that we should...

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Planets known in Ancient Times Mercury difficult to see; always close to Sun in sky Venus very bright when visible — morning or evening “star” Mars noticeably red Jupiter very bright Saturn moderately bright Retrograde motion: Like the Sun, planets usually appear to move eastward relative to the stars. We pass them by in our orbit…. Easy for us to explain: occurs when we “lap” another planet (or when Mercury or Venus lap us) But very difficult to explain if you think that Earth is the center of the universe! In fact, ancients considered but rejected the correct explanation…
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Why did the ancient Greeks reject the notion that the Earth orbits the sun? It ran contrary to their senses. If the Earth rotated, then there should be a “great wind” as we moved through the air.
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Unformatted text preview: Greeks knew that we should see stellar parallax if we orbited the Sun – but they could not detect it. Parallax Angle Apparent shift of a star’s position due to the Earth’s orbiting of the Sun Parallax angles of the star are so small, that you need a telescope to observe them. The nearest stars are much farther away than the Greeks thought. Stars are so far away that stellar parallax is too small for naked eye to notice Earth does not orbit Sun; it is the center of the universe Unfortunately, with notable exceptions like Aristarchus, the Greeks did not think the stars could be that far away, and therefore rejected the correct explanation (1)… Thus setting the stage for the long, historical showdown between Earth-centered and Sun-centered systems....
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Planets known in Ancient Times - Greeks knew that we should...

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