1. Early Astronomers & Planetary Motion

2. Vocabulary Terms
Perihelion – when a planet is closest to the sun in its orbit.
Aphelion – when a planet is farthest from the sun in its orbit.
Ellipse – the oval shaped path that a planet takes around the sun.
Geocentric Model of SS – Earth is at the center of the SS
Heliocentric Model of SS – Sun is at the center of the SS

3. PTOLEMY (90 – 168 AD)

4. PTOLEMY (90 – 168 AD) Roman Astronomer, mathematician, and geographer
Thought Earth was at the center of the solar system (Geocentric model
of the SS)
Thought that all the
planets traveled in smaller
circles, called epicycles.

5. COPERNICUS (1473 – 1543)

6. COPERNICUS (1473 – 1543) Scientist during time of Renaissance
Thought the sun was the center of our SS
(Heliocentric model of SS)
Also proposed the idea that Earth was tilted
He and his followers had to study in secret

7. Galileo (1564 – 1642)

8. Galileo (1564 – 1642)
He was the first to use telescopes to observe space
He discovered 4 moons around Jupiter
He discovered the phases of Venus
He observed the surface of the moon and the sun.

9. BRAHE (1564 – 1601)

10. BRAHE (1564 – 1601)
Built an observatory and recorded the positions of the stars and planets for 20 years.
At age 20, he was in a duel and lost part of his nose. He wore a metal insert over the missing part.

11. KEPLER (1571 – 1630) Brahe’s assistant and mathematician
Published the Laws of Planetary Motion in 1609 – 1618.

12. KEPLER'S FIRST LAW OF PLANETARY MOTION
Kepler's First Law of Planetary Motion states that the orbits of the planets are ellipses with the sun at one focus of the ellipse.

13. KEPLER'S SECOND LAW OF PLANETARY MOTION
Equal Area Law - states that a line from a planet to the sun will sweep out equal areas in equal times. The planet moves more slowly when it is farther from the sun and faster when it is near it.

14. KEPLER'S THIRD LAW OF PLANETARY MOTION
Harmonic Law – states that the farther a planet is from the sun, the slower its speed and the longer its period of revolution.

15. SIR ISAAC NEWTON (1642 – 1727)

16. UNIVERSAL LAW OF GRAVITATION
The Universal Law of Gravitation states that the force of gravity between two objects is dependent on the mass of the objects and their distances from each other.

17. Early Astronomers & Planetary Motion

18. Vocabulary Terms
Perihelion – when a planet is ___________ to the sun in its orbit.
Aphelion – when a planet is ___________ from the sun in its orbit.
Ellipse – the oval shaped path that a ________ takes around the _______.
Geocentric Model of SS – ________ is at the center of the SS
Heliocentric Model of SS – _________ is at the center of the SS

19. PTOLEMY (90 – 168 AD)

20. PTOLEMY (90 – 168 AD)
________ Astronomer, mathematician, and geographer
Thought ______ was at the center of the solar system (_________ model
of the SS)
Thought that all the
planets traveled in smaller
circles, called __________.

21. COPERNICUS (1473 – 1543)

22. COPERNICUS (1473 – 1543) Scientist during time of ________________
Thought the ______ was the center of our SS
(____________ model of SS)
Also proposed the idea that _____ was ______
He and his followers had to _______ in secret

23. Galileo (1564 – 1642)

24. Galileo (1564 – 1642)
He was the first to use ___________ to observe ______
He discovered 4 moons around ________
He discovered the __________ of Venus
He observed the ________ of the _______ and the _______.

25. BRAHE (1564 – 1601)

26. BRAHE (1564 – 1601)
Built an ___________ and recorded the positions of the _______ and _________ for 20 years.
At age 20, he was in a _____and lost part of his ______. He wore a metal insert over the missing part.

27. KEPLER (1571 – 1630) Brahe’s _________ and mathematician
Published the _____ of Planetary ______ in 1609 – 1618.

28. KEPLER'S FIRST LAW OF PLANETARY MOTION
Kepler's First Law of Planetary Motion states that the ______ of the planets are ______ with the _____ at one focus of the ellipse.

29. KEPLER'S SECOND LAW OF PLANETARY MOTION
______ Area Law - states that a line from a planet to the sun will sweep out _____ areas in equal times. The planet moves more ______ when it is farther from the sun and ______ when it is near it.

30. KEPLER'S THIRD LAW OF PLANETARY MOTION
_________ Law – states that the _______ a planet is from the sun, the slower its ______ and the longer its period of __________.

31. SIR ISAAC NEWTON (1642 – 1727)

32. UNIVERSAL LAW OF GRAVITATION
The __________ Law of Gravitation states that the force of _______ between two objects is dependent on the _____ of the objects and their _______ from each other.