Question

How is the distance between the earth and moon calculated?

Answer 1

6378 sin(`alpha`/2 ) sin`theta`/2). `alpha` is parallax when Moon is seen, at same instant, from two places. `theta` is angle subtended at Earth's center by the join of the two locations..

Explanation:

Observe Moon;s center on a Full Moon night from two places 100 km apart for parallax `theta`.. Then `alpha` = 100/6378 radian = 0.0156789 radian = 0.8983346 deg. The distance of the Moon then will be approximately 6378 sin(0.449167)/sin (`theta`/2). The other way about , if the distance is known to be 384000 km, theta is nearly 0.1492 deg = 54", nearly.. .