WILL Smith has celebrated his 50th birthday with a bungee jump from a helicopter near the Grand Canyon. In scenes that wouldn't be out of place in a movie, the actor shouted: "This is some of the most beautiful stuff I've ever seen in my life." Smith said the experience was like going from "pure terror to absolute bliss". As he hung over the chasm, he added: "Oh my God, this is gorgeous, this is gorgeous." Smith was greeted by friends and relatives and was interviewed by Fresh Prince Of Bel-Air co-star Alfonso Ribeiro, aka Carlton, before he jumped. Speaking afterwards, Smith said: "I am not going to be able to articulate it thoroughly right now but here's a real…