how do find it out?

Question

how do you determine Earth's circumference? can u tell me the steps for finding the earth's circumference? thanks ;D

Answer 1

"Eratosthenes (276 BC - 194 BC) estimated Earth's circumference around 240 BC. He had heard about a place in Egypt where the Sun was directly overhead at the summer solstice and used geometry to come up with a circumference of 250,000 stades. This estimate astonishes some modern writers, as it is within 2% of the modern value of the equatorial circumference, 40,075 kilometres."

To be honest, it's a bit fuzzy for me, but I think what Eratosthenes did was cut a stick of some exact length and stuck it in the ground. At noon, the stick did not cast any shadow. Later it did. He measured all the lengths both ways. Remember from geometry that the square of the hypotenuse is equal to the sum of the squares of the other two sides (A sq + B sq = C sq). Then he moved the whole show an exact distance away (several hundred kilometers) and did everything again. Now he had 2 sets of exact numbers because all the lengths were short enough to measure accurately. By comparing the two sets of numbers, he could estimate the circumference of the Earth (because he also knew how far apart the experiments were done).

Answer 2

Find the radius or diameter. C=2 pi times r(adius).

Once you know the distance from the earth to the moon, and knowing the moon's diameter, the earth's diameter is easy to calculate.