Some materials allow light to pass through them; others allow only some light through; and others block all the light and create a dark shadow on any surface beyond them, where the light cannot reach. Mirrors can be used to redirect a light beam. (Boundary: The idea that light travels from place to place is developed through experiences with light sources, mirrors, and shadows, but no attempt is made to discuss the speed of light.) What other questions did this lead to?

Patterns of the motion of the sun, moon, and stars in the sky can be observed, described, and predicted.

Seasonal patterns of sunrise and sunset can be observed, described, and predicted.