How Can You Measure Time Using a Shadow Stick?

Choosing the Right Stick

Select a straight, sturdy stick about 10-15 cm (4-6 inches) tall, with a dark object like a rock or a piece of bark to mark the shadow’s edge. This will help you spot the shadow’s movement and make the measurements more accurate. Avoid using a stick with a wide base, as it may not cast a clear shadow.

Measuring Shadow Length

Mark two points on the ground where the shadow falls at different times, using the dark object to mark the shadow’s edge. Record the time it took for the shadow to move from the first point to the second. For example, if the shadow moved 10 cm (4 inches) in 30 minutes, you can calculate the shadow’s rate of change (10 cm / 30 minutes = 0.33 cm per minute). You can use this rate to estimate the time elapsed between any two shadow lengths.

Estimating Time Elapsed

To estimate the time elapsed between two shadow lengths, divide the shadow length difference by the shadow’s rate of change. For instance, if the shadow length increased by 20 cm (8 inches) and the rate of change is 0.33 cm per minute, you can estimate the time elapsed as follows: (20 cm) / (0.33 cm/min) = 60.61 minutes. This method is not as accurate as a watch, but it can give you a rough estimate of the time of day when you don’t have a watch or other time-keeping device.