By Michael Lanza
My seven-year-old daughter, Alex, is engaged in some heavy intellectual lifting. I can tell by the way she stares quietly, her brow knitted in thought, at Upper Yosemite Falls. We’ve hiked for 90 minutes up a thousand vertical feet of hot, dusty trail above Yosemite Valley to stand below this curtain of water that plunges a sheer 1,430 feet off a cliff, ripping through the air with a sound like fighter jets buzzing us.