Presentation on theme: "Homework, HW#1 due today Announcements Questions? Tuesday, January 22"— Presentation transcript:
1 Homework, HW#1 due today Announcements Questions? Tuesday, January 22 Spring 2008
2 The Scientific MethodScenario: Your phone hasn’t rung in several days, but your friend says s/he tried calling you.Task: Come up with a few different hypotheses that would explain why your phone hasn’t rung and how you would test them.
3 Chapter 2: The Ordered Universe Newton’s laws of motion and gravity predict the behavior of objects on Earth and in space.
4 Our (place in the) Galaxy near infrared map of the Milky Way GalaxyEstimated Diameter of “Observable Universe” = 78 billion light-years1 light-year ≈ 5.9 trillion milesNGC 7331(Milky Way’s galaxy twin)Rotational speed of solar system ,000 MPHSpeed of the Milky Way ,000 MPHSpeed of “Local Group” ,367,000 MPHOur speed relative to the universe 65,000 MPH
5 Our (place in the) Solar System orbits of the inner planetsorbits of the planetsEarth orbital characteristics:Avg. Distance from Sun 93 million milesLength of orbital path 574 million milesOrbital eccentricityAvg. orbital speed 66,622 MPHRotational speed (equator) MPHAxial tilt °relative sizes of the planets
6 Observing patterns in nature – application of knowledge Stonehenge, ~2800 B.C.= 500 people50,000 kg100 kg / person
9 Ptolemy and the explanation of retrograde motion Claudius Ptolemaeus (90 – 168 AD)Retrograde motion: the apparent backward motion of a planet relative to the fixed stars.retrograde motion (animation)
10 Ptolemy and the explanation of retrograde motion retrograde motion predicted by epicycles (animation)Ptolemy introduces planetary epicycles: the epicycle is a sphere embedded in the planet’s celestial sphere. Together, these spheres move the planet.
11 Copernicus and the heliocentric system All planets orbit the sun in perfect circles.Earth rotates on an axis through its center.Easier to explain retrograde motion.Epicycles still utilized.Does not provide completely accurate predictionsNicolaus Copernicus (1473 – 1543)Copernicanheliocentric theory
13 Tycho Brahe’s view on planetary motion The last great naked-eye astronomer (telescopes did not exist while he was alive)Constructed a large quadrant to make highly accurate measurements of the positions of the planets and starsTycho Brahe (1546 – 1601)
14 Chapter 1 quiz in class on Thursday 01/24 Read pp of Chapter 2 in the textbook for Thursday 01/24