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Homework, HW#1 due today Announcements Questions? Tuesday, January 22 Spring 2008.

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Presentation on theme: "Homework, HW#1 due today Announcements Questions? Tuesday, January 22 Spring 2008."— Presentation transcript:

1 Homework, HW#1 due today Announcements Questions? Tuesday, January 22 Spring 2008

2 The Scientific Method Scenario: 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 Galaxy NGC 7331 (Milky Way’s galaxy twin) Rotational speed of solar system 497,000 MPH Speed of the Milky Way 89,000 MPH Speed of “Local Group” 1,367,000 MPH Our speed relative to the universe65,000 MPH Estimated Diameter of “Observable Universe” = 78 billion light-years 1 light-year ≈ 5.9 trillion miles http://en.wikipedia.org/wiki/Hubble_sequence

5 Our (place in the) Solar System orbits of the inner planets orbits of the planets relative sizes of the planets Earth orbital characteristics: Avg. Distance from Sun 93 million miles Length of orbital path 574 million miles Orbital eccentricity 0.017 Avg. orbital speed 66,622 MPH Rotational speed (equator)1040 MPH Axial tilt23.4°

6 Observing patterns in nature – application of knowledge = 500 people 50,000 kg 100 kg / person Stonehenge, ~2800 B.C.

7 Plato, Aristotle, Ptolemy: The Heavenly Spheres

8 The Celestial Sphere

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 Ptolemy introduces planetary epicycles: the epicycle is a sphere embedded in the planet’s celestial sphere. Together, these spheres move the planet. retrograde motion predicted by epicycles (animation)

11 Copernicus and the heliocentric system Nicolaus Copernicus (1473 – 1543) 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 predictions Copernican heliocentric theory

12 The heliocentric system and retrograde motion

13 Tycho Brahe’s view on planetary motion Tycho Brahe (1546 – 1601) 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 stars

14 Chapter 1 quiz in class on Thursday 01/24 Read pp. 30-40 of Chapter 2 in the textbook for Thursday 01/24


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