I find myself fulfilling a lifelong dream as I float down the Colorado River on a large inflatable raft with 13 other adventurers and two guides. The air is hot but cool breezes intermittently arise from the cold river water to deflect the heat. Beneath us, the olive-green water rushes through the greatest geologic chasm in the world, the iconic Grand Canyon. All are silent as we absorb the majesty of this natural spectacle…