[subsubzero]

agree, firing ion beams to make the mirror perfect one molecule at a time(they are declared the most precise mirrors on earth). This stuff is beyond wild. Not that I believe this stuff came from alien technology but if anything could be said to have not originated on earth this would be a strong candidate. And barely a hundred years ago we just figuring out flight at kitty hawk and now you have technology like this, its really amazing.

[on_the_train]

Everyone loves the electron beam etching. But no one asks how they know where to etch, which is what the most expensive machines do, I.e. mirror surface metrology. It's surprisingly hard to "just measure" the shape and roughness of these things