Supersymmetry is a theory which stipulates that for every known particle there should be a partner particle. For instance, the electron should be paired with a supersymmetric 'selectron,' quarks ought to have 'squark' partners, and so on.

String theory envisions a multiverse in which our universe is one slice of bread in a big cosmic loaf. The other slices would be displaced from ours in some extra dimension of space.

We know that if supersymmetric particles exist, they must be very heavy; otherwise we would have spotted them by now.

Brian Greene Quotes