Homework, HW#1 due today
Announcements
Questions?
Tuesday, January 22
Spring 2008
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.
Chapter 2: The Ordered Universe
Newton’s laws of motion and gravity predict the behavior of objects on Earth
and in space.
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 universe 65,000 MPH
Estimated Diameter of “Observable Universe” = 78 billion light-years
1 light-year ≈ 5.9 trillion miles
http://en.wikipedia.org/wiki/Hubble_sequence
Our (place in the) Solar System
orbits of the inner planetsorbits 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 tilt 23.4°
• Observing patterns in nature – application of knowledge
= 500 people50,000 kg
100 kg / person
Stonehenge, ~2800 B.C.
Plato, Aristotle, Ptolemy: The Heavenly Spheres
The Celestial Sphere
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)
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)
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
The heliocentric system and retrograde motion
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
Chapter 1 quiz in class on Thursday 01/24
Read pp. 30-40 of Chapter 2 in the textbook for
Thursday 01/24