Classroom Participation Exercises

Here is a list of cool classroom participation exercises for intro to Astronomy courses. If you have an idea or proved demonstration, please email me, and I will post it ( lwl @ illinois . edu).

Angular size scales.
Concept: This can be used to help explain parallax or angular size vs. distance.

First explain how a fist and fingers can be used to estimate angular size. Then stand in front and have them estimate your angular size. If you want you can give the formula for distance.

Then call out angles (or distances). Point out that those at the far end found small angles, and those close-by found large angles.

Concept: For orbits, there must be a force changing the veloity.

Doughnut on a string. Swing the doughnut in an orbit. Eventually the doughnut flies off tangent to the orbit in a straight line. There must be a force to cause orbits. Ah.. gravity.

Far side of the Moon
Concept: To demolish the idea of the Dark Side of the Moon.

Pick a volunteer to be the Earth. Then, another student to be the Moon, holding a Moon globe with Far Side and Near Side yellow sticky-ed to the globe. Have another student play the Sun with a lamp.

Have the Earth volunteer rotate fast to indicate that the Earth is rotating faster than the Moon orbits. But also show that the "Dark Side" of the moon is actually only the Far Side, and is frequently lit with the "Sun". This can also demonstrate that the Moon rotates.

Scattered Light (Why is the Sky blue?)
Concept: Blue light is more scattered than Red light.

Take an transparent glass of water and place on the overhead. Then add just a little of CoffeeMate (TM). The projected image will get red colored, and the glass viewed from the side will appear bluer.

Hydrostatic Equilibrium
Concept: Hydrostatic Equilibrium keeps the Sun up.

Use a balloon and low it up. Explain pressure. How does a balloon work. Use a liquid nitrogen dewar. Explain how a dewar works. Pour liquid nitrogen on the balloon and watch it shrink. Explain how the pressure inside was reduced and the balloon shrank. Analogy to the Sun-- Fusion pressure and gravity.

Concept: To show that sunspots are still bright although they show up as dark on the Sun.

Use an incandescent lamp with a variable control. Project lamp through overhead projector. With the right curent, the element will project black, so you can see the element. Take it off of the the overhead projector, and they class can see that it is very bright. Then back to the overhead to show a homemade sunspot.

Expansion of the Universe
Concept: To show that in an expanding Universe, the Hubble law is universal.

You need 1 viewgraph with random dots to illustrate the galaxies. Then another that has been enlarged with the photocopier by about 2%. First show viewgraph 1, and explain Hubble's Law. If we were the center dot, we would see the farther dots move away faster than the nearer dots. Draw them.

Overlay viewgraph 1 and 2 with the center (we are here) dots align. You will see the farther galaxies have moved the most, the nearby the least. Now, pick another galaxy. And overlay it in viewgraph 1 and 2 to show that from the perspective of that galaxy Hubble's Law is also true.

Leslie Looney
Last modified: Mon Jan 31 17:50:32 CST 2005