How to find how far is the moon from earth using solar eclipse?
Imagine an isosceles triangle with the sun at the base and the earth at the vertex. Now imagine the moon as a line segment connecting the two legs, parallel to the base and near, but not at the vertex. Drop the bisector from the vertex to the base (it bisects the moon as well). Now you have similar triangles: the large one with the sun at the base and earth at the vertex, and a smaller one with the moon as the base and the earth at the vertex. If you know the width of the base, and the distance from the earth to the sun (the vertical bisector), you can use a little algebra to compute the distance from the moon to the earth (that smaller bisector from the moon to the earth.
