A student holds a lit flashlight and walks slowly to the far end of the gym. The class keeps watching, and the flashlight looks dimmer and dimmer. What changed?

At night the stars look like faint points of light, but the Sun is far too bright to look at. What mainly explains this difference in how bright they look from Earth?

At night a boy sees a car's headlights far down a straight road. As the car drives toward him, the headlights look brighter and brighter. Did the car's lights change?

The Sun is the closest star to Earth.

Star A and Star B look about equally bright in the night sky. Scientists find that Star A is far more distant from Earth than Star B. What must be true about Star A?

Three stars each give off about the same amount of light. Star X is 20 units away, Star Y is 60 units away, and Star Z is 200 units away. Which star looks brightest from Earth?

A class models star brightness by setting two bulbs at different distances from the viewer. To keep the test fair, what must stay the same?

A student claims the Sun looks brightest to us mainly because it is the closest star. What observation would best support that claim?

Imagine a spacecraft traveling for years straight toward a distant star. During the trip, how does that star look to the crew, and why?

Stars are still in the sky during the day, but we cannot see them. What best explains why?

The Sun gives off more light than any other star in the sky.

A classmate says every star in the night sky is the same distance from Earth. Is the classmate correct?

A student says the Sun looks brightest to us because it is the biggest star in the universe. What should a classmate say to correct this?

A girl holds a lit candle at arm's length while a large campfire burns far across a dark field. The candle looks brighter to her than the campfire does. What does this show?

A class wants to model why the Sun looks brighter to us than other stars do. What setup would model this best?

How bright a star looks from Earth is its apparent brightness. Star M and Star N give off the same light, but Star M is 10 units away and Star N is 90 units away. Which observation best supports the claim that brightness depends on distance?

Stars give off huge amounts of light, yet they look faint from Earth. Why does a light look dimmer when it is farther away?

Suppose the Sun could be moved as far from Earth as other stars are, with nothing else about it changed. How would it look from Earth?

Two friends see a very faint star and disagree about it. One says the star must be small, and the other says it may only be far away. What should they find out first?

The star Sirius gives off far more light than the Sun does, yet from Earth it still looks like a small point in the night sky. What best explains this?