1. Who was Ptolemy?
2. Who was Nicolas Copernicus?
- 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?
4. Who was Johannes Kepler?
5. Describe Kepler’s laws.
- 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.
7. Who was Isaac Newton?
- 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?
9. Who found the Dwarf Planet Ceres?
- 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?
- John Couch Adams and Urbain Le Verrier. 1846
- They believed this because there were wobbles in the orbit of Uranus.
11. Who found Neptune?
- Johann Galle and Heinrick D’arrest
- Based on Le Verrier’s predicted position.
12. Who discovered Pluto?
- 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.