Answer:
the diameter of the moon
Explanation:
The first distance to be measured with any accuracy was that of the Moon. In the middle of the 2nd century BCE, Greek astronomer Hipparchus pioneered the use of a method known as parallax.
Historically, the first person to measure the distance to the sun was the Greek astronomer Aristarchus around the year 250 B.C. He used the phases of the moon to measure the sizes and distances of the sun and moon. During a half moon, the three celestial bodies should form a right angle.
