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Origins: Where are the Aliens?

Viewing Ideas  Print this Teacher's Guide (PDF, 20 pages)

Origins: Earth is Born Viewing Ideas
Origins: How Life Began Viewing Ideas
Origins: Back to the Beginning Viewing Ideas

Before Watching

1. To help students understand that the light they see from stars is a snapshot of what happened long ago, have them consider light from the sun. If the sun stopped shining, how long before anyone on Earth would see it "go out"? (150 x 10⁶ km ÷ 3 x 10⁵ km/sec =500 seconds, or 8.3 minutes) Explain to students that when they look at a star at night, they are seeing the light that left the star long ago, not the light that it is currently radiating.

2. Take a poll on how many students believe there is intelligent life elsewhere in the Milky Way galaxy. Ask students to support their reasoning for or against the existence of intelligent life.

After Watching

1. In 2004, Epsilon Eridani was the nearest Milky Way star believed to harbor a planet. It resides 100 trillion kilometers from Earth. Have students calculate how long it takes light to get to Earth from Epsilon Eridani using the fact that light travels at a speed of 3.0 x 10⁵ km/sec (1.0 x 10¹⁴ km ÷ 3.0 x 10⁵ km/sec = 3.3 x 10⁸ sec, and then 3.3 x 10⁸ sec ÷ 3.16 x 10⁷ sec/yr = 10.4 years)

2. Repeat the poll about intelligent life. How do the results compare to the earlier poll? Have students explain any changes in thinking. Have students further consider the pros and cons of finding intelligent life. Students can and register their own votes at www.pbs.org/nova/origins/aliens.html

3. Ask students what they think life might look like on another planet. Do they think it would be similar to life on Earth? Why or why not? What are the challenges involved in finding life?