When Billy Idol first entered American consciousness in the early '80s, leather-clad and bleached hair in tow, he not only brought a punk rock sound to the mainstream. The Englishman brought a new ...

A weathered sign in the Minnesota River Valley proudly proclaims: “World’s Oldest Rock.” Erected in 1975, it marks a 3.8-billion-year-old gneiss — or so scientists thought.