Looking out at the Night Sky
What questions do you have?
Motions in the Sky:
How does the sun move during the day? How do stars move
during the night?
Does the motion of the sun change with the seasons?
Does the sun set at the same point along the horizon (from the
same location)?
Do the stars change with the season?
How about the motion of the moon? How does the shape
change?
What else…?
Activity
1. Let’s explore these questions with a globe. (what are we
assuming about the earth when we do this?)
How long does the earth take to rotate once?
Which direction does it rotate? (east? west? )
When do we see the stars?
How long does it take the earth to revolve around the sun?
Ok: the north star, or Polaris, or “the star that does not
walk”; why does it have this name? Use your
planisphere (star wheel) for this.
The Earth as a top: let’s experiment with tops…
Next Activity:
Becoming the earth (aka kinesthetic astronomy)
let’s form a circle around our sun, with your head
representing the earth. I will tell each of you what month it
is on your “earth”
Using your star wheel, decide what constellation is
overhead at midnight!
Next, we introduce the “tilt” of the earth
Terms we will use: horizon, zenith, ecliptic, angles
Motions in the Sky: More Questions
Are there stars we never see
in Arizona?
Are there stars that never go
below the horizon in
Arizona?
How do stars move if we are
at the north pole? Do they
rise and set?
The Large Magellanic Cloud
Where is the north star if we are at the equator?
When the sun is high in the sky in Arizona where is it in the sky
in Rio de Janiero? When it is low in our sky, where is it in Rio?
Lecture Tutorial, p. 3 Part 1: Looking North
Work with someone else, and ask me if you are confused!
Use the props I brought!
Use your star wheel from class 1!
For those people with more background, continue to part
II: Looking East
The Moon:
How much does the moon change from day to
day? Why does it change?
“It’s not science if we can’t measure it!”
We will be measuring the position of the moon, of sunset,
and of Venus for much of the semester.
How could we do this? How was it done in the past?
Angles and units for measuring them: degrees
(How many degrees in a circle?)
Terms:
Azimuth: angle around the
horizon measured from north
through east
Altitude: angular distance
from horizon to object.
We can use our fist as a pretty good estimate of angles.
For greater accuracy, we can use a compass to measure
azimuth: free download on your ipad
Or a magnetic compass is just fine: I
have a few
Measuring angles, or altitude : Let’s build a protractor for
measuring angles, or angular diameter, in degrees
Next, let’s go measure the moon! Angular size? Altitude?
Homework:
Concepts covered this class:
Daily motion, stars, sun
Height of north star, path of stars in sky
Seasonal change of constellations
Intro to motion of moon
Measuring angles, protractor
Terms: horizon, zenith, angles (angular diameter), azimuth&
altitude
The sun, image taken through a solar filter. How
big would the moon be if taken with the same
camera?