======Measuring the Sun’s Size with a Pinhole Viewer======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
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**Alternative titles:** Pinhole Viewer Sun Measurement
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====Summary====                   
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====Procedure====  
  - Cut a square about 1.5 cm by 1.5 cm from the center of the cardboard.
  - Tape the aluminum foil over the opening so it completely covers the hole.
  - Use a pin or thumbtack to carefully make a tiny hole in the center of the foil.
  - Go outside on a sunny day and hold the cardboard so sunlight passes through the pinhole.
  - Hold a piece of white paper behind the pinhole to catch the Sun’s projected image.
  - Increase the distance between the pinhole and the paper as much as possible while keeping the image clear.
  - Measure the diameter of the circular Sun image on the paper and record it.
  - Measure the distance from the pinhole to the paper using string or a ruler and record it.
  - Use the ratio d/l = D/L to calculate the Sun’s diameter, where d is image size, l is pinhole distance, and L is the distance from Earth to the Sun.



====Links==== 
Astronomy at Home Kid's Experiment - Build a Pinhole Camera and Measure the Size of the Sun - Dr Brad Tucker: 
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Measuring Space - Creating a Pinhole Viewer - UHS STEM Academy: 
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📄 Size of the Sun - Weber State University: [[https://physics.weber.edu/schroeder/astro/sizeofsun.html]]\\

📄 Measure the Sun’s Size - The Laurence School of Science: [[https://www.nisenet.org/sites/default/files/catalog/uploads/diy_ss_measure_sun_size.pdf]]\\

====Variations====
  * Tape the white paper to a book to help keep it upright.
  * Use a tablet or smartphone screen as a light source in a dark room to measure the screen size.
  * Compare results using different pinhole sizes.
  * Have students work in groups and compare calculated values.



====Safety Precautions====
  * Never look directly at the Sun.
  * Do not look through the pinhole at the Sun.
  * Keep the viewer pointed away from faces and eyes.
  * Supervise younger students when working outdoors.




====Questions to Consider====
  * Why does the pinhole create a circular image of the Sun? (The Sun is roughly spherical, and the pinhole projects its shape.)
  * How does increasing the distance between the pinhole and the paper affect the image size? (The image becomes larger.)
  * Why can ratios be used to calculate the Sun’s real size? (The geometry of similar triangles applies.)
  * Why is the calculated value different from the actual diameter of the Sun? (Measurement errors and limitations of the setup.)