1. "Last is D, the number of spatial dimensions. Due to interest in M-theory, physicists have returned to the question of whether life is possible in higher or lower dimensions."
- Michio Kaku, Parallel Worlds: A Journey Through Creation
2. "Consider the apparent dimension of the universe. According to M-theory, space-time has ten space dimensions and one time dimension. The idea is that seven of the space dimensions are curled up so small that we don’t notice them, leaving us with the illusion that all that exist are the three remaining large dimensions we are familiar with."
- Stephen Hawking, The Grand Design