How do science concepts apply to your world? Here are some questions you'll be able to answer after you read this chapter.

• How can the sun disrupt radio and TV signals on Earth?
• How do we know what stars are made of?
• What has such strong gravity that not even light can escape from it?
• Where were the atoms that make up your body formed?
• What is at the center of our galaxy?
• Is the universe expanding?
• What is the large-scale structure of the universe?

Can You Tell How Bright a Light Really Is?

Procedure

1. Work in groups of three or four. Obtain two flashlights, one brighter than the other.
2. Predicting   If the dimmer flashlight moves close enough to you, will it appear brighter than the other flashlight? Record your prediction.
3. Darken the room. Have two group members stand side by side about 3 meters from the rest of your group. Each one should shine a flashlight at the group.
4. Direct the person with the dimmer flashlight to slowly move closer to the group, keeping the flashlight level.

Think About It

1. Observing   Was your prediction correct?
2. Drawing Conclusions   How does the distance from you to a light affect how bright the light appears to you?
3. Applying Concepts   If one star appears to be brighter than another star, can you tell which one is actually brighter just by looking at them? Explain your answer.