1. Who was Ptolemy?
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First Geocentric Model of universe. Ancient Greece.
2. Who was Nicolas Copernicus?
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First Heliocentric model of the Universe.
The belief that the Earth and all the other Planets orbited the sun. 1543 on the revolutions of the Celestial Spheres (De Revolutionibus Orbium Coelestium)
Book Published on death-bed Afraid of what Church would do to him.
Retrograde motion only explainable with Heliocentric model. Theory only accepted in late 16th century.
3. Who was Tyco Brahe?
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Danish Astronomer. Purpose built observatory in Copenhagen. Made various observations. Died of Mercury poisoning.
4. Who was Johannes Kepler?
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Tyco’s assistant. Formulated laws of planetary motion. 1’st two laws published in New Astonomy in 1609. 3rd law published in Harmonies of the Word in 1619.
5. Describe Kepler’s laws.
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1st law
Planets move in elliptical orbit around the sun. Sun was at one focus of each ellipse.
2nd law
Planet’s speed is related to distance from sun. (In diagram below, the planet moves faster near the Sun, so the same area is swept out in a given time as at larger distances, where the planet moves more slowly. The green arrow represents the planet’s velocity , and the purple arrows represents the force on the planet .) The closer to the sun the faster the orbit.
The diagram below illustrates the 2nd law: “A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.”
3rd law
The orbital period of a planet is directly proportional to it’s mean distance from the sun Expressed as:
T squared=R cubed Where T = number of earth years to orbit the sun And where R = the average distance from the sun in AU
6. Name some of Galileo Galilei’s discoveries.
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The moon was not spherical
that it contained mountains and craters
Venus’s phases
Were exactly like the moon
Jupiter’s four satellites
Callisto Europa Ganymede Io
7. Who was Isaac Newton?
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He came up with the Theory of Gravity. Found the force of attraction on two objects in directly proportional to the product of their masses. Found out that the were inversely proportional to the square of the distance between them This is called the inverse square law.
distance between two objects doubles, force is one quarter of original value (1/4 = 0.25 which is the inverse of 2 squared)
8. Who discovered Uranus?
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William Herschel in 1781. Used home-made telescope from the garden of his house in Bath. Had particular interest in naked eye stars.
Mistook Uranus for a star.
Herschel tracked the star to find an orbit He was then able to work out that the object was a planet.
9. Who found the Dwarf Planet Ceres?
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Sicilian astronomer Giuseppe Piazza in 1801 Astronomers predicted another planet in between Mars and Jupiter Piazza found faint star moving in position over several successive nights.
Believed it was a new comet Fell ill and unable to observe it.
Carl Friedrich Gauss and von Zach determined that this was a planet.
10. Who predicted the existence of a planet beyond Uranus?
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John Couch Adams and Urbain Le Verrier. 1846
They believed this because there were wobbles in the orbit of Uranus.
11. Who found Neptune?
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Johann Galle and Heinrick D’arrest
Based on Le Verrier’s predicted position.
12. Who discovered Pluto?
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Edward Pickering and Percival Lowell
Believed (incorrectly) that a second planet influenced wobbles on Uranus.
Clyde Tombaugh
Received Edward and Percival’s predictions located the planet photographically. 1930.
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