Sophie’s Shadow Clock

Sophie wants to know when Grandpa’s garden game will begin. “When that post’s shadow reaches the path,” he jokes. But the shadow is long in the morning, and she cannot tell which way it will move. They decide to investigate before trusting his shadow clock.

Grandpa fixes a short post upright on level ground. Sophie places a large sheet of paper beside it and marks the shadow’s tip. They record the time separately in a notebook. The Sun lights the ground, while the post blocks some light and makes a shadow.

They secure the paper so it cannot turn or blow away. The post must stay in the same place too. Otherwise a changed shadow mark could simply mean their equipment moved. Sophie draws the post’s position and checks that nobody is standing across the light.

Later, the shadow points in a different direction and is shorter. Sophie marks its tip again. “The post has not moved,” she says. Grandpa explains that the Sun appears to travel across the sky as Earth turns. Changing light direction changes where the shadow falls.

They return at intervals, marking each new tip and recording the time. The shadow’s length changes as the Sun appears higher or lower in the sky. Near the middle of the day, it is shorter than in the early morning. Sophie compares marks instead of guessing from memory.

A cloud passes across the Sun. The shadow becomes faint and difficult to mark clearly. Sophie writes down the cloudy conditions rather than inventing a neat tip. Their method depends on clear enough sunlight. A shadow clock cannot work equally well in every kind of weather.

By late afternoon, the shadow is longer again and points another way. Sophie joins the observations in her notebook. Their marks show a pattern for this post on this day. In a different season or place, the marks would be different. They cannot use today’s pattern to tell the time everywhere.

Grandpa brings out the garden game. “Can our clock replace every clock?” he asks. “No,” Sophie says, “but it helped us notice something.” They play beside their drawing as the evening light stretches across the lawn. Sophie has kept her appointment with a moving shadow.