1. Chapter 1 The Copernican Revolution
Lecture Outline
Chapter 1 The Copernican Revolution

2. quiz Show SEM map and view from earth for following phases
Full moon
Waning gibbous
3rd quarter ½ moon
Lunar eclipse
Show SEM system with proper distances in proportion

3. In the news

4. 9 sept: Chapter 1 The Copernican Revolution

5. Units of Chapter 1 Preview the chapter…. The Motions of the Planets
The Birth of Modern Astronomy
The Laws of Planetary Motion
Newton’s Laws
Summary of Chapter 1

6. Who is Aristarchus of Samos?
250 BC, the time of the first critical, non-mystical thinkers in Greece
Could see the sun was big by the earth’s shadow on the moon
Reasoned that the Earth should orbit around the bigger sun
This idea was lost for 1600 years as Asia and Europe slipped into mystical thinking

7. 1.1 The Motions of the Planets
The Sun, Moon, and stars all have simple movements in the sky, consistent with an Earth-centered system.
But the Planets:
(Show on Stellarium)
Move with respect to fixed stars
Change in brightness
Change speed
Have retrograde motion
Are difficult to describe in earth-centered system

8. 1.1 The Motions of the Planets
A basic geocentric model, showing an epicycle (used to explain planetary motions)

9. 1.1 The Motions of the Planets
Lots of epicycles were needed to accurately track planetary motions, especially retrograde motions. This is Ptolemy's model.

10. 1.1 The Motions of the Planets
A heliocentric (Sun-centered) model of the solar system easily describes the observed motions of the planets, without excess complication.
So, what is the primary advantage of the heliocentric model?..

11. *13 sept; 1.2 The Birth of Modern Astronomy
Observations of Galileo:
The Moon has mountains, valleys, and craters.
The Sun has imperfections, and it rotates.
Jupiter has moons.
Venus has phases.
All these were in contradiction to the general belief that the heavens were constant, perfect, and immutable.

12. 1.2 The Birth of Modern Astronomy
The phases of Venus are impossible to explain in the Earth-centered model of the solar system.

13. The birth of modern astronomy
Watch until 10:45, modern physics

14. From this video, know Aristotle Ptolomy Renaissance Copernicus
Tycho brahe
Kepler
Galileo
Newton

15. 1.3 The Laws of Planetary Motion
Kepler’s laws:
1. Planetary orbits are ellipses, Sun at one focus.

16. **1.3 The Laws of Planetary Motion
Kepler’s laws:
2. Imaginary line connecting Sun and planet sweeps out equal areas in equal times.
When an orbiting planet or comet is near the sun, it goes fast, and when it’s far away, it goes slowly.

17. 1.3 The Laws of Planetary Motion
Kepler’s laws:
3. Square of period of planet’s orbital motion is proportional to cube of semimajor axis.
Compare this to Kepler’s second law.
The period of a planet goes up as the radius of the planet increases

18. Who was Kepler? The greatest astronomer. Born 1571.
Worked for Tycho Brahe (“teesho”)
Analyzed motion of the planets, worked out laws of planetary motion
An interesting 20 min video of this history
plus
Video is a little dense

19. 1.3 The Laws of Planetary Motion
The Dimensions of the solar system
The distance from Earth to the Sun is called an astronomical unit. Its actual length may be measured by bouncing a radar signal off Venus and measuring the transit time.

20. 1.4 Newton’s Laws
Newton’s laws of motion explain how objects interact with the world and with each other.
Newton’s first law:
An object at rest will remain at rest, and an object moving in a straight line at constant speed will not change its motion, unless an external force acts on it.

21. 1.4 Newton’s Laws a = F/m Newton’s second law:
When a force is exerted on an object, its acceleration is inversely proportional to its mass:
a = F/m
Newton’s third law: know this one!!!!
When object A exerts a force on object B, object B exerts an equal and opposite force on object A.

22. 1.4 Newton’s Laws
Gravity
On Earth’s surface, the acceleration due to gravity is approximately constant, and directed toward the center of Earth.

23. 1.4 Newton’s Laws
Gravity
For two objects, the gravitational force is proportional to the product of their masses divided by the square of the distance between them.
The closer they are, or the bigger (more massive) they are, the harder they pull on each other.

24. 1.4 Newton’s Laws
Gravity
The gravitational pull of the Sun keeps the planets moving in their orbits.
Compare to a spinning ball on string….

25. 1.4 Newton’s Laws Two or more Massive objects orbit around each other.
look at and see binary star or double double to see various types of orbit.
Set to show double star
wobble of sun
Speed of orbit depending on elliptical position

26. 1.4 Newton’s Laws
Kepler’s laws are a consequence of Newton’s laws.

27. 21 sept. Quiz on chapter 1 The shape of every orbit is
Circle b. square c. parabola d. ellipse
Which was NOTan observation of Galileo?
The Moon has mountains, valleys, and craters. B. The Sun has imperfections, and it rotates. C. Jupiter has moons. D. Venus has moons
Which of these people was NOT part of the Copernican revolution
Copernicus b. Aristotle c. Kepler d. Newton
What is the force that holds all planets, moons, comets, asteroids, galaxies, and stars in their orbits?
a. Gravity b. Magnetism c. Jedi d. Mass

28. Look at variation with time Why change size Moon on sept 27, 9:40pm
18 Sept 2015 Quiz on Stelarium
Find your object
Any moons? Their period
Magnitude, phases
Look at variation with time
Why change size
Moon on sept 27, 9:40pm
Turn on equatorial grid
Find your zodiac constellation
Where was the moon when you were born?

29. Summary of Chapter 1
First models of solar system were geocentric, but couldn't easily explain retrograde motion.
Heliocentric model does.
Galileo's observations supported heliocentric model.
Kepler found three empirical laws of planetary motion from observations.

30. The varieties of orbital motion
Look at the range of possibilities
Check: why are only stable orbits present in our solar system & galaxy?
Are all orbits stable? Examples….

31. Summary of Chapter 1, cont.
Laws of Newtonian mechanics explained Kepler’s observations.
Gravitational force between two masses is proportional to the product of the masses, divided by the square of the distance between them.

32. Update on New Horizons

33. Show this tool in google earth

34. NY Times yesterday

35. Practice for exam 1
1) In an annular eclipse, A) the Moon is totally blocked by the Earth. B) the Sun is partially blocked by the Earth. C) the Moon appears as a thin, bright ring. D) the Sun appears as a thin, bright ring. E) the Sun is totally blocked by the Moon.
2) The interval from new Moon to first quarter is about a(n) A) month. B) day. C) hour. D) year. E) week.
3) Put these important scientists in proper order of when they lived and worked a. Galileo, b. Copernicus, c. Newton, d. Ptolomy, e. Kepler