Conceptual Physics (12th Edition)

Published by Addison-Wesley
ISBN 10: 0321909100
ISBN 13: 978-0-32190-910-7

Chapter 1 - Reading Check Questions (Comprehension): 7

Answer

Aristarchus waited until the time of the half moon so that the sunlight would be striking the moon at right angles to his line of sight. The lines connecting Earth and the moon, the moon and the Sun, and the Sun and the Earth would form a right triangle. He then used trigonometry to calculate the distance from Earth to the Sun.

Work Step by Step

This is explained in figure 1.5 on page 6.
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