1. Space-time Lego Willem Westra And Stefan Zohren

2. Our goal Find a theory of Gravity for very, very small scales Einstein’s theory of gravity: works well for big things such as stars and planets Small scales: Quantum Mechanics...

3. The big stuff: Gravity Einstein’s theory of general relativity, 1918

5. Gravity: curvature of space-time Matter curves space-time Curved space-time tells matter how to move Gravity = Geometry

6. The small: Quantum mechanics Schrödinger’s equation, 1927

8. Quantum Mechanics Everything that can happen... does happen What we see is the stuff that is most probable to happen

9. big + small gravity + quantum curved space-time + probability

10. Curved space + quantum Task: count all possible curved space-times Compute the most probable ones Solution: build space time from little “Lego blocks” Count the number of ways the Lego blocks can be put together

11. 1+1 dimensional space times One dimension of space One dimension of time Simplest Lego blocks: triangles Task: count the number of ways one can glue triangles together

12. Counting the triangles N NN

13. N N+1

14. An example

68. Splitting the universe N N+1 N

69. The standard equation N N+1 N

70. Missing a move? N N+1 N