> here is nothing that says an enormous, impossibly thin solar sail can't be formed by randomly bashing an infinity of rocks together over a near-infinity of ti

> here is nothing that says an enormous, impossibly thin solar sail can't be formed by randomly bashing an infinity of rocks together over a near-infinity of time Nobody is saying that it is impossible, the author is simply saying that it seems unlikely that is the origin. It's Occam's razor, whereby the simplest solution seems to not be alien intelligence or serendipitous solar sails, but rather something that we have seen appear naturally (fractals).