Guiding Questions

• How fast does light travel? How can this speed be measured?

• Why do we think light is a wave? What kind of wave is it?

• How is the light from an ordinary light bulb different from the light emitted by a neon sign?

• How can astronomers measure the temperatures of the Sun and stars?

• What is a photon? How does an understanding of photons help explain why ultraviolet light causes sunburns?

• How can astronomers tell what distant celestial objects are made of?

• What are atoms made of?

• How does the structure of atoms explain what kind of light those atoms can emit or absorb?

• How can we tell if a star is approaching us or receding from us?