Homework, HW#1 due today

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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