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Venus Transit
Background Reading
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MATH
Astronomers could not measure the distance to Venus and the Sun without using a geometric principle well-known to land surveyors:
Triangulation. Astronomers use a modified version of this principle. To find the distance to a planet or other astronomical object, instead
of measuring the base angles A and B which is what a surveyor would do, you measure the vertex angle, P. For the transit of Venus,
observers on the Earth at A and B will be separated by thousands of miles. Venus will appear at different places on the distant Sun. By
measuring the angle shift between the two spots on the Sun in degrees, you can determine the vertex angle, and from the baseline
distance A to B, determine the distance to Venus.
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Would you like to measure the transit of
Venus safely? Use a Sunspotter to track
Venus across the sun. Then, send-in your
results to NASA and join other students
in measuring the distance to the Sun
yourself! Here are the directions in a PDF
document:
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This drawing is from the June 3,1769
transit of Venus, and shows the details
of the path across the sun at that time.
No two observers at different latitudes
will see the path cross in exactly the
same places.
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