Day 3 comments on the Introduction and start Chapter 1

1
Day 3 comments on the Introduction and
start Chapter 1
2
Simulations shown in class

• With permission from Rick Pogge of Ohio State
  Univ, I showed some simulations from his two
  Astronomy course web sites
• http//www.astronomy.ohio-state.edu/pogge/Ast161/
  Movies/
• http//www.astronomy.ohio-state.edu/pogge/Ast162/
  Movies/
• He has a simulation of what the Big Dipper would
  look like if you went back 100,000 years and
  watched for 200,000 years.
• (we showed the big dipper movie)
• We will come back to the idea of proper motion in
  Ch. 10.

3
Ch. 1 The Copernican Revolution

• The development of the current model of the solar
  system began with careful measurement of the
  movement of the Sun and the Moon.
• To understand this, lets review the motion and
  the phases of the Moon, as we currently
  understand them.
• When we watch the Moon, its shape changes from
  one night to the next

4
From the astronomy picture of the day web site
( link )
5
Lunar Phases
6
Ch. 1 section 1.1 Motion of the Planets

• The motion of the Moon and Sun seemed fairly
  simple, almost like they were moving in circles
  around the Earth. The Moon moves from west to
  east on the celestial sphere in a very orderly
  way. (ST article)
• Five other objects did NOT move in this simple
  way. They are the planets, the wanderers in the
  Heavens.
• The planets usually move from west to east on the
  celestial sphere, but not always.
• The most perplexing aspect of the planets motion
  is motion in the opposite direction, from east to
  west, called retrograde motion, which occurs on a
  regular basis.

7
Planetary Motionsinclude Retrograde
motionshow marsretro95.mov
8
Retrograde motion occurs over several weeks, and
involves motion to the west, as compared to
prograde motion, which is to the east(relative
to the stars of the celestial sphere).
9
Geocentric Model of planetary motion (Greek
philosophy)
10
The Geocentric Model does explain retrograde
motion, using concepts like deferent and
epicycle. These could be illustrated by swinging
a ball on a cord as we revolve a center of an
epicycle around the Earth. (class demonstration
here)
11
Ptolemys Model of planetary motion used
deferents (big circles) and epicycles (little
circles centered on a point that moves on the
deferent). This involved up to 80 circles to
describe 7 objects!
12
Nicholas Copernicus and his Heliocentric model of
the Solar System explained this in a simpler way
with the Sun at the center.
13
The Heliocentric Model also explains the
Retrograde Motion of the planets.
14
More illustrations of retrograde motion, using
Earth and Mars as the example.
15
(No Transcript)
16
(No Transcript)
17
Retrograde Motion of Mars as seen from Earth
18
Galileo Galilei and the Birth of Modern
AstronomyGalileo built a telescope in 1609 and
looked at the sky.
Four objects The Moon The Sun Jupiter Venus
(and much more)
19
Galileo looked at the Moon and saw mountains,
craters, valleys, and topography like you might
find on the Earth. The Moon was perhaps an
object like the Earth!
By projecting an image of the Sun, he could see
imperfections on the Sun. Sunspots could be seen
to move from east to west on the Sun and he
deduced that the Sun rotated about once a month.
20
Galilean Moons of Jupiter Small point of light
could be seen near Jupiter. By observation
during several weeks he deduced that these were
moons and that they revolved around Jupiter.
Perhaps this planet was like the Earth, with
several moons of its own. It also seemed like
a miniature model of the heliocentric solar
system.
21
Venus Phases in the Heliocentric modelThese are
consistent with the observations in a telescope.
22
Venus Phases in the Geocentric model are
obviously wrong as soon as you observe with a
telescope
23
Eyes on the Skies

• A production in conjunction with the
  International Year of Astronomy - 2009
• Honors the use of the telescope by Galileo 400
  years ago in 1609
• 5 parts lets look at the first part on the
  historical telescopes
• Pay attention to the part about Galileo and the
  four objects of attention Moon, Jupiter,
  Sunspots, and the phases of Venus.

24
Exam 1 is next Tuesday

• Feb. 3, after some class discussion
• Closed book, no notes
• Multiple choice and true/false
• Answer on a Scantron form (pencil)