1. Conceptual Physics http://mrlafazia.com/PHYS111/lessons/201011Fall/PHYS111_20.ppt THURSDAY October 28 th, 2010 LESSON GOALS: Introduction to Unit 3 (Scope & Sequence) Discussion and definitions on Planetary Motion Review simulation on Perihelion and Aphelion Introduce Newton’s Law of Universal Gravitation Take an historical view of Planetary Motion Discuss the origins of Earth’s solitary Moon Go through a series of Lunar discussion questions as a class If we do not finish these tonight, we will pick up with them next time. Read poem entitled Lunacy 1/22 Note: Because of the question-heavy nature of this powerpoint, I have already taken the liberty of uploading it to our Course Documents folder on Blackboard.

2. Unit 3: “Earth & Space” Scope & Sequence This unit relates all that we have learned in the previous 2 units to the large-scale physical world we experience and observe. Planetary Motion Newton’s Law of Gravitation Lunar (MOON) concepts Big Bang Theory Solar System Evolution Plate Tectonics & Continental Drift Boundary Phenomena Earth’s Magnetic Field (brief overview) – Estimated Time Needed: approximately 5 or 6 days, depending on class speed 2/22

3. Planetary Motion “How is it related to circular motion”? Describing planetary motion – Orbit, revolution; rotation definitions What force causes this circular motion? Does it truly follow a circular orbit? – Ellipse discussion (more vs. less eccentric orbits) “How does the motion change (and why) along an orbit”? Perihelion and aphelion definitions 3/22

4. Online Simulation http://www.windows2universe.org/physical_science/physics/mechanics/orbit /perihelion_aphelion.html The above simulation gives a very simple but exacting view of the difference between what occurs at the perihelion and aphelion of an orbit. 4/22

5. Law of Universal Gravitation m 1 and m 2 = masses of two objects d = distance between objects’ centers of mass G = gravitational constant – 6.7 x 10 -11 N·m 2 /kg 2 We will get some opportunities to work through examples of this formula! 5/22

6. A Brief History of Planetary Motion 6/22

7. The old old days… Ancient Greece – Things rose or fell according to what they were Smoke rises Objects fall Gave birth to the terms – Levity (lightweight) – Gravity (heavy) 7/22

8. Stargazing Always the popular past time, early humans noticed that celestial bodies moved in regular patterns – Planet = “wanderer” Tycho Brahe (1546-1601) – Extremely detailed measurements of planetary motion – Built first observatory (an entire island!) – Had precise instruments constructed Side Note: Don’t forget Galileo! 8/22

9. Johannes Kepler One of Brahe’s assistants and a brilliant mathematician Used heliocentric (sun-centered) model and Brahe’s measurements to discover basic descriptions for the behavior of every planet and satellite (moons, comets, etc.) – “fatal” blow to church-enforced geocentric description – Verified Copernicus’ ideas Those 3 descriptions are now known as Kepler’s 3 laws of planetary motion. 9/22

10. The falling apple About 45 years after Kepler – Isaac Newton saw an apple fall, and also observed the moon in the daytime sky – What’s keeping the moon from flying off into space? – Force that makes the apple fall must be causing the moon to continually “fall” toward Earth 10/22

11. A universal force He named this force gravity, and he said it existed between every single object! The amount of force depends on: – How massive the objects are More mass = more force – The distance between the objects Closer together = more force 11/22

12. Newton vs. Einstein: clash of the titans! Newton said that gravitational forces permeated instantly… – Suppose the sun disappeared… Einstein said that gravitational effects would take time to feel 12/22

13. Einstein’s Ideas Gravity is not a force, but a “bend” in space More massive bodies will cause a greater bend 13/22

14. Discussion: Earth’s Solitary Moon What are some theories you have about the Moon’s origins? Which of these is “right”? 14/22

15. Lunar Study Questions We will now look at a number of important questions. These questions will fuel our discussion on Moon concepts. Pay special attention to how you might be able to pull from your past classes in this course to answer the questions presented (if only for the satisfaction of knowing that you are entering into some level of Physics fluency!) 15/22

16. Lunar Study Questions 1-4 1) What two reasons make the surface of the Moon so easy to see from the Earth? 2) Give two reasons for why the Moon has no atmosphere. 3) What allows the Earth’s temperature between night and day to not change as much as it does on the Moon? 4) It is usually said that we see the same “face” of the Moon all of the time. WHY is this the case? (Side- question: Do we really just see this single face?) 16/22

17. Lunar Study Questions 5-8 5) Use Newton’s Law of Universal Gravitation to find the Weight of an 80 kg person on the Moon. (We will need to find the mass of the Moon and the Moon’s radius). 6) This Weight should be 1/6 that applied on the Earth’s surface. Is it? Why or why not? 7) “Swear not by the Moon—the ever changing Moon!” Why is this Romeo and Juliet quote so apt when discussing the Moon? 8) Why do we have different “phases” of the Moon? 17/22

18. Lunar Study Questions 9-13 9) How does a partial or total eclipse of the Sun occur? 10) How does a partial or total eclipse of the Moon occur? 11) When does a full moon occur? 12) How does the Moon’s diameter compare to the Earth’s? 13) Why do the Sun and Moon appear to be approximately the same size “in the sky” even though the Sun is able to encompass millions of Moons within itself? 18/22

19. Lunar Study Questions 14-18 14) What might happen if the Earth did not rotate on its own axis as it revolves around the Sun? 15) Explain what happens with high and low tides. 16) Considering the Sun’s effects (about 1/3, gravitationally, as the Moon’s), when would you get the biggest difference between high and low tides? 17) Why is the Moon getting further and further away from the Earth (i.e., why is it “less tightly bound”)? 18) How is the Moon (theoretically) supposed to “meet its end” if given enough time…? 19/22

20. Recommended Reading: 20/22 p. 105, Sections 6.1 – 6.5, 6.7 – 6.11 Note: The text does not offer much specific help on Earth and Space topics, so we will rely mostly on outside sources for our references for the majority of this unit.

21. POEM: Lunacy, by D. LaFazia 21/22 Earth's natural satellite Gives people quite a fright Causing solar eclipses (it sure scared the Gypsies!) But Earth shows its cold shoulder To that giant boulder By blocking the sunlight (day seems just like night!) Round and round it dances Further away it romances From the Earth it does stray (but it won't stay that way!) Someday when all's said and done When spinning's had its fun The Moon will not then depart (but rather it will break apart!) There's more to that lunatic prance But leave it to happenstance I must here this poem end (the Moon is peaking round the bend!) Goodnight

22. Looking Ahead: 22/22 Next class will begin our Unit 3 content!