As a child in Palo Alto, California, he built an atom smasher in the garage. He later became one of the founders of string theory. Today, with his flowing mane of silver locks, Michio Kaku is one of ...

A Mars-size object called Theia smashed into Earth, and the debris coalesced into the moon. Now scientists believe they may have identified pieces of Theia at the bottom of Earth’s mantle. A new study ...