A105
Stars and Galaxies
Today’s APOD
Homework 3 due Sept. 14
EM Radiation
Read units 21, 22, 23
News Quiz on Tues., Sept. 12
Observing the Full Moon
Opportunities!
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Rooftop Sky Viewing: Sept. 14, 20
Solar Lab: Sept. 20, 2:00 PM
Remote Observing: Sept. 15, 16
10-11 PM, Swain West 403
• SCOPEOUT in Cincinnati: Sept. 16
• www.cincinnatiobservatory.org/scopeout
The Sun Today
Solar
Orbiting
Heliospheric
Observatory
(SOHO)
Orbits between the Sun and
Earth, about a million miles away
– a constant view of the Sun
Last Thursday
Visualizing
Space
Expert Methods for
Visualization
Draw diagrams
Use 3d models
Use visualization
software
If you have a chance, visit
a planetarium…
Visualize the
Earth from
Space
• Pretend you are
Superman!
• What do you see?
–
–
–
–
Earth
Moon
Sun
Stars
Copyright 1980 by DC Comics Inc.
Welcome to
Outer Space!
Which of the following four diagrams most accurately
depicts the Earth's orbit around the Sun?
The Solar System from Overhead
• space.jpl.nasa.gov
Zooming In
The Inner Solar System
The Solar System
from “Overhead”
• 91,369,000 miles on Jan 4 (minimum)
• 94,776,000 miles on July 4 (maximum)
• average distance is 92,918,000 miles
• Varies +/- about 2% from a perfect
circle
Basic Ideas
• The Earth orbits the
Sun in one year
(revolves)
• The Earth spins
around once each day
(rotates)
• The Moon orbits the
Earth about once a
month (revolves)
Where are
Mars, Earth
the Moon
and the
Sun?
The Earth and Moon from Mars
Visualizing the
Earth in Space:
What causes the
Seasons…?
True or False?
The Earth has seasons because…?
• The Earth moves closer to or farther
from the Sun - it’s closer in the
summer and farther in the winter.
December
Weather
IU’s Rose
Well House
Bondi Beach Sydney, Australia
When is the Earth closest to
the Sun?
A.
B.
C.
D.
Winter
Spring
Summer
Fall
Visualizing
Seasons –
What really
happens?
• Textbook applet: cause_of_seasons.htm
Which of the following
best explains why it is
hotter in Indiana in June
than it is in December?
A
The Sun gives off
more heat energy
in June.
B
The Northern Hemisphere
is closer to the Sun in June.
C
The Sun is higher in the sky
and and provides more hours
of daylight in June.
D
Earth is closer to
the Sun in June.
With thanks to Bill Watterson, 1990
Visualizing the Moon
How can we understand
the phases of the Moon
as it circles around the
Earth?
Galileo Galilei's "The Phases of the Moon"
Image courtesy of Biblioteca Nazionale
Florence, Italy
Sometimes the Moon
looks like this
And sometimes the
Moon looks like this
What causes the Moon to change its appearance in
this way?
A. As the Moon orbits Earth, Earth's shadow covers the
Moon.
B. Clouds block part of the Moon from our view so it is
full sometimes and covered other times.
C. As the Moon orbits Earth, the part of the Moon
facing Earth is facing away from the Sun.
The
Earth
and
Moon
from
Space
Thinking about the Moon
• How much of the Moon receives sunlight at a given
time? Always half the Moon? Sometimes more or
less than half? Why?
• During new moon (when the moon appears dark) is
sunlight falling anywhere on the Moon's surface?
If not, why not? If so, why don't we see it?
• Is the Earth or the Moon closer to the Sun at new
moon?
• Which is closer to the Sun at full moon?
The Moon moves in its orbit about 12
degrees per day
It rises about an hour later each night.
Why?
Bring the perspective back to Earth
Ansel Adams; copyright © 2000 George Eastman House, Rochester, NY
Understanding the Moon in the Sky
I’m really
way off to
the right
Now
I’m
right
here!
Moon and Venus
before Dawn
Where are the
Earth, Moon and Sun
in 3-dimensional
space?
Where is Venus?
The Libration of the Moon
Read units 21, 22, 23
News Quiz on Tues., Sept. 12
Observing the Full Moon
Homework 3 due Sept. 14
EM Radiation