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(p.4) |
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| Finding the AU: Calculation of the Sun-Earth Distance | ||||||
| Besides the angle V, the only other thing we need to know is the distance between the two observers on Earth, at points A and B. | ||||||
Call
this distance  . |
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Then,
to get the distance from Venus to Earth, all we need is basic trigonometry.
There is a right triangle formed between the Earth and Venus. |
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| Or, rearranging the equation: | ||||||
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| For small angles, tan (1/2 A) = 1/2 tan A, so: | ||||||
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Once we
have the distance between Earth and Venus
, it’s easy to find the distance from the Earth to the Sun,
again using Kepler’s
third law. This law tells us that the distance between the Earth
and Venus is .28 times the distance between the Earth and the Sun. |
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| So: | ||||||
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