I just want to start off by saying that my knowledge of Astronomy (and physics, for that matter) is pretty limited, so please don't laugh too hard if I make an ass of myself. I'm taking the first Astronomy course at my University, and today my professor briefly mentioned that the arc angle when looking at the sun is .5 inches and it is the exact same for the moon (I may be off on the measurement, but that's not the point I'm driving at). Because this is so, a lunar (and/or?) solar eclipse is possible. As someone who probably thinks too often in Darwinian terms, I asked my professor what the natural advantage of this is. He said it was a good question, but he did not know the answer. Does this help anything (sun, moon, the 'orbit' itself, earth, etc.) in any way? Long ago, was there perhaps some sieving process which left us with a moon that could block out the sun so as to help itself and/or the moon (or something else)? So basically, why is it that the moon and sun have the same arc angles? Is it just random chance? Is it because it helped it to survive over billions of years? I know that I might be applying this thinking to too broad of a question, but I just can't convince myself it happened by accident. Or maybe it did... If there is no answer for this question I would appreciate an educated assumption. Yours would certainly be better than mine. Thanks for your time.