Most hikers who day hike Whitney start @ midnight, so it's common practice to hike that trail at night. Coming up from Whitney Portal is a nice safe trail & no edges to worry about. Coming in from Guitar Lake is a more dangerous hike & most folks from that side hit the trail @ 2 am to catch a sunrise. I remember watching the stream of headlamps on the switchbacks as I cowboy'd at guitar lake, pretty cool!! Surreal Hike, Enjoy!!