This website describes all universes that could possibly exist by exploring boundaries in physics and nature. If we imagine our expanding universe in reversed time, space contracts until it reaches an infinitely small point. If we imagine the future of accelerating expansion there is an extreme where the universe is stretched totally flat. The singularity at the beginning of time and flat space at the end of time are extreme conditions, beyond which no other possibilities exist, not only for our human imagination but for nature and reality.

Links to tutorials and review articles in theoretical physics.