# Measuring the Diameter of the Sun and the Moon *

 Difficulty Time Required Short (2-5 days)
*Note: This is an abbreviated Project Idea, without notes to start your background research, a specific list of materials, or a procedure for how to do the experiment. You can identify abbreviated Project Ideas by the asterisk at the end of the title. If you want a Project Idea with full instructions, please pick one without an asterisk.

## Abstract

You can measure the diameter of the Sun (and Moon) with a pinhole and a ruler! All you need to know is some simple geometry and the average distance between the Earth and Sun (or Moon). An easy way to make a pinhole is to cut a square hole (2-3 cm across) in the center of a piece of cardboard. Carefully tape a piece of aluminum foil flat over the hole. Use a sharp pin or needle to poke a tiny hole in the center of the foil. Use the pinhole to project an image of the Sun onto a wall or piece of paper. Use a ruler to measure the diameter of the projected image. Use your knowledge of geometry to prove that you can calculate the diameter of the Sun using the following proportionality:

Important Safety Note: Never, ever look directly at the Sun. You can permanently damage your eyes (UC Regents, 2001).

### MLA Style

Science Buddies Staff. "Measuring the Diameter of the Sun and the Moon" Science Buddies. Science Buddies, 2 Sep. 2014. Web. 22 June 2017 <https://www.sciencebuddies.org/science-fair-projects/project_ideas/Astro_p026.shtml>

### APA Style

Science Buddies Staff. (2014, September 2). Measuring the Diameter of the Sun and the Moon. Retrieved June 22, 2017 from https://www.sciencebuddies.org/science-fair-projects/project_ideas/Astro_p026.shtml

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Last edit date: 2014-09-02

## Bibliography

UC Regents, 2001. "Finding the Size of the Sun and Moon," The Center for Science Education @ Space Sciences Laboratory, University of California, Berkeley [accessed July 31, 2006] http://cse.ssl.berkeley.edu/AtHomeAstronomy/activity_03.html.

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