“In string theory – an idea that’s been around since the late 1970s – the universe is a 10-dimensional place, with six of those dimensions curled up inside themselves like a cat in front of a fireplace. All particles and forces are different resonances and vibrations of these 10-dimensional strings. Strings are far from the only game in town. There are other, potentially equally promising approaches to unifying physics’ two seemingly incompatible visions of the cosmos: general relativity and quantum mechanics.”