Teacher

Teacher's Guide for:

Geography Under the Stars

Objectives:

To find our directions at night using the North Star or Polaris.
To try to find evidence that the Earth, is, in fact, a sphere.
To see how the sky seems to change as we travel across the Earth’s surface.

This show conforms to the following state science standards: 11.A.1c, 12.F.1b, 12.F.2a, 12.F.2c

Brief Show Summary:
How do we know the Earth is round? Think about it!! It’s not easy to show a round Earth unless you look at photos from space-and those are flat! How did the Greeks convince themselves, many years before Columbus, that the Earth is a sphere? These are topics covered in the show. After a few of the current constellations are spotted, we travel to both the North Pole, Equator and South Pole to see how the sky changes as we venture across the curved surface of the Earth. See Alpha Centauri, the closest star to us besides the Sun and see why we can’t see that star from Central Illinois. Student volunteers actually try their hand at measuring their latitude by using only the stars and their fists! If time permits, the seasons and the “midnight Sun” can also be covered. Determining longitude is more complicated and isn’t covered in this program.

Pre-visit Discussion & Activities:
1) “What is the shape of the Earth?” Challenge students to prove to you how they know the Earth is round. What evidence can you give? What would it be like to travel across a flat Earth? A round Earth?
2) Discuss the North Star and why it’s the North Star. Most will say you can “find your way home.” Well, yes, if you live in the north! The North Star is NOT the brightest star – far from it – but it’s high above the Earth’s north pole so, as the Earth spins, all the stars appear to move, but the North Star does not move. That’s why it’s important! Have students spin around slowly and locate a point on the ceiling for them that won’t seem to move. You can also put the star dots on the inside of an umbrella and spin it over an Earth globe’s north pole. Stars that never set are called “circumpolar.”
3) Use clay and build a “small” mountain to place on a globe. Put your eye as close to the edge of the globe as possible and then slowly turn the globe. What happens to the mountain? How would this work on a flat Earth?

Post-visit Discussion & Activities:
1) How can a lunar eclipse show that the Earth is round? Could their be other explanations? Could the Earth be pizza-shaped?
2) A fist held at arm’s length subtends an arc of about ten degrees. A smaller student will have a smaller fist but also a shorter arm, so it all works out. Using your fists, measure the heights of some objects. How high (in degrees) is a distant tree? If you know the distance to the base of the tree, a little trigonometry will give you the tree’s actual height.
3) Challenge students to find a star (preferably the North Star) on their own and measure it’s height above the horizon in fists. It should be four fists high, but record the answers you get. If you travel farther towards the equator, what happens to the fist height of Polaris? How about a trip to the equator?
4) Why were there very few sea-faring civilizations below the Earth’s equator? Use a star map and show there isn’t a “south star.”

Vocabulary
Latitude Rotation Revolution “Midnight Sun”
Circumpolar Lunar Eclipse Constellation

Internet resources:
On-line star charts: http://SkyandTelescope.com/observing/skychart/
Latitude page: http://www.ruf.rice.edu/~feegi/
The Champaign-Urbana Astronomical Society & Observatory: http://www.prairienet.org/cuas