Measure the Sun’s Size

In this activity, learners make their own pinhole viewer in order to measure the size of the sun. After using the viewer to project circular image of the Sun on paper, learners use ratios and an equation to calculate the Sun’s real size. Step-by-step instructions are included with photos along with important safety guidelines. This activity needs a sunny day, however an alternative is provided using the light from a tablet in a dark room. Activity guide includes a helpful section on the required equation and variables, and a “What’s going on?” explanation on how the pinhole viewer works.

Materials List:

• sheet of cardboard (like from a cereal box)


• piece of white paper


• small piece of aluminum foil (about 3 cm x 3 cm)


• pin or thumbtack


• scissors


• tape


• ruler


• string or yarn (about 60 cm long)


• hardcover book (optional)