Bobby Zimmerman of Hibbing, Minnesota, relocated to New York City and precisely 50 years ago, set the world on fire. Having been personally re-imagined as Bob Dylan, he captured the hearts and minds of music lovers in lower Manhattan - and then everywhere. Some of his earlier songs like ''Blowin' in the Wind'' seemed to have been in existence eternally, and he was quickly some kind of mystic presence on the music scene. But even that quick renown would never satisfy Dylan, who would always push forward, onward, outward. He went electric at Newport with his backers in the Band, horrifying the folk purists. He ventured into the drug culture - he turned the Beatles on to marijuana - and his songs got denser, trippier. But they were always lyrical and meaningful, and though he always disdained the term, he was undoubtedly a voice of his generation. Fifty years on, it is time to celebrate Bob Dylan and recount his extraordinary journey. ''LIFE'' was there when Bob and Joan Baez were kids in the Village, and photographers like Elliott Landy were there every subsequent step of the way, chronicling the story. Here is that story - Bob Dylan's story - in words and pictures.''LIFE ''is amused that Dylan once wrote a sarcastic song, ''Ballad of a Thin Man,'' about a newsweekly reporter who was trying to figure him out. The reporter, way back in the '60s, wasn't affiliated with ''LIFE'' - but no matter. All these years down the road, we're still looking at Bob. Maybe there's another song to be written?