In this activity, learners use their hands as tools for indirect measurement. Learners explore how to use ratios to calculate the approximate height of something that can't be measured directly by first measuring something that can be directly measured. This activity can also be used to explain how scientists use indirect measurement to determine distances between things in the universe that are too far away, too large or too small to measure directly (i.e. diameter of the moon or number of bacteria in a volume of liquid).
In this activity, learners use their feet to estimate distances. Learners calculate the distance of one step in centimeters by measuring 10 steps at a time to reduce measurement error. Learners can use their stride ruler to measure the distance between different points on the playground as an extension activity.