What Do You Think?

On a clear, moonless night in an area with very little air pollution, a person with normal vision can see over 2000 stars.

• Why do stars appear as "points" of light, having no apparent size, even when viewed through the most powerful telescopes?
• How big are stars and how far away from Earth are they?

Record your ideas about these questions in your Active Physics log. Be prepared to discuss your responses with your small group and the class.

For You To Do

1. Work with others in your group to identify various kinds
of light sources.

a) Record in your log at least three kinds of natural light sources in the sky. Add to the list later in this activity if you think of more sky-based sources.

b) Indicate whether you think each kind of natural light source in the sky produces light from within (L), or reflects light from another source (R).