Why Do Big Objects Look Small From Far Away?

Why do big objects look small from far away? Try this easy activity at home to learn how this applies to the Sun, Moon and eclipses!


This video was created in collaboration with the Sci-Tech Discovery Center. This work is supported by the Simons Foundation and is part of its ‘In the Path of Totality’ initiative.

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Transcript: Have you ever looked at an object far away and tried to pinch it between your fingers? That object may have been very large, but because you were a long distance from it, it appeared small. This phenomenon is called “apparent size”. This concept combines math and science to explain how objects are viewed from various distances. Try this- Get two balls of different sizes. Place one ball on a table or eye level surface. Hold the other ball in your outstretched arm. Close one eye and slowly walk backwards until both balls appear the same size to you. To demonstrate, we’ve got our Moon here, which is about 3 inches in diameter, and the Earth, which is about 12 inches in diameter. The real Moon is about ¼ the diameter of the Earth, so this model is to scale. Let me show you how this works! Wow! Even though the objects are very different in size, they appear the same when far apart. This is why the Moon can eclipse the entire Sun, even though its diameter is 400 times smaller! It’s also very difficult to get the Earth, Moon, and Sun to line up perfectly to create a total solar eclipse. Because the Moon and Earth have elliptical, or oval shaped, orbits, their distances change. If the Moon is too far away from Earth to block the entire Sun, it’s called an annular eclipse. This is why total solar eclipses are so rare and special! The Total Solar Eclipse happening on April 8th is the last one in the continental US for 20 years, so make sure you check out the links below for more information on how you can view this awesome astronomical event.



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