On Sunday, while you were doing anything else, two guys who live near Yosemite Valley, Jason Torlano and Zach Milligan skied the iconic shoulder of Half Dome, continuing all the way to the valley floor below, descending thousands of feet until they reached the frozen shores of Mirror Lake. At least once before, Half Dome itself had been skied, but not all the way to the valley’s bottom. Torlano is a longtime first descender of ski lines throughout Yosemite. He’d been scouting a Half Dome line for years, finally deciding this weekend that the snow would allow it. ADVERTISEMENTThe two hiked to the base of Half Dome on Saturday, woke at dawn on Sunday, trudged to the top of the dome and looked down.