"Our brains aren't trained to see anything other than our world, and it will likely take something from another dimension to make us understand. But what is this other dimension? Mystics used to see it as a place where spirits lived, since they weren't bound by our earthly rules. In his theory of special relativity, Einstein called the fourth dimension time, but noted that time is inseparable from space. Science fiction aficionados may recognize that union as space-time, and indeed, the idea of a space-time continuum has been popularized by science fiction writers for centuries. Einstein described gravity as a bend in space-time. Today, some physicists describe the fourth dimension as any space that's perpendicular to a cube -- the problem being that most of us can't visualize something that is perpendicular to a cube ..."
