Why Does the Size of the Sun Appear to Change?
ES2603  Measure the Earth-Sun Distance

The closer we are to an object, the larger it appears. The farther we are from the object, the smaller it appears. If you know how large the object actually is, you can measure its apparent size and use it to calculate the distance to the object.

  !   Use the measuring tool on the left to measure the diameter of the solar image for each month. The difference in the diameter from one month to the next is very small, so measure carefully!



3. For each solar image, record the solar diameter, in pixels, in the table.

To convert the sun's diameter in pixels to its distance from Earth in millions of km, divide 71,060 by the diameter you measured. For example, a measured solar diameter of 467 pixels represents a distance of 71,060/467 or 152.2 million km.

4. Calculate the distance to the sun for each month in millions of kilometers and record it in the table.


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