Christian high wire artist Nik Wallenda will attempt to cross the Grand Canyon on a tightrope, and this time without a harness, to make history. The Discovery Channel will air live his most daring feat yet on Sunday evening. Wallenda, who is 34 and a married father of three, says he is looking forward to crossing the canyon. "Part of my Niagara dream was taken away because I had to wear a tether," he tells People magazine, referring to his feat last summer when ABC required him to wear a harness, though he still became the first man in history...