1. Adventures in String Theory Science One, April 7 th, 2011

2. What are the basic building blocks of nature?

3. Old Answer Air Earth Fire Water

4. Modern Answer Modern physics: understand in detail how nature works at distances 100,000,000,000,000 times smaller than we can see!

5. The Standard Model of Particle Physics All matter made of elementary particles -different masses and spins Forces arise from basic interactions of these particles Rules for interactions determined by quantum mechanics and special relativity ~20 parameters electromagneticstrong weak

6. The Basic Building Blocks? AirEarth FireWater ProtonNeutron ElectronPhoton

7. Questions Why this set of particles and interactions? Are these particles really elementary? Are there more particles or forces? What about gravity?

8. General Relativity

9. Accurately predicts gravitational effects from solar system dynamics to the evolution of the whole universe. Predicts new phenomena, e.g. black holes, gravity waves, expansion of the universe

10. How did the universe begin?

11. Old Answer

12. Modern Answer: the Big Bang General relativity universe has expanded and cooled for 13.6 billion years from extremely hot, dense state

13. Questions What happened in the first instant of the big bang (or before)? What is inside a black hole? We need a quantum mechanical theory of gravity!

14. String Theory: the Basics Basic building block: string (1 dimensional loop of energy) Quantum mechanics Specific vibrational modes with definite energy and angular momentum We see: particles with different mass and spin m = E/c 2

15. String interactions time Particle interactions arise from splitting and joining of strings

16. String interactions Particle interactions arise from splitting and joining of strings

17. String interactions Particle interactions arise from splitting and joining of strings

18. String interactions Particle interactions arise from splitting and joining of strings

19. String interactions Particle interactions arise from splitting and joining of strings

20. String interactions

21. Basic law of string physics: Strings move to minimize the area of their worldsheet

22. String physics: strings vibrate, join, split via basic law + quantum mechanics We see: various types of particles with forces arising from basic interactions INCLUDING gravity String theory automatically gives a theory of quantum gravity and particle physics with no parameters!

23. Extra Dimensions Surprise: even the number of dimensions is fixed! We see: 4 String theory predicts: 10 BUT: recall that space can be curved

24. Garden-variety extra dimensions Our universe: Hose universe:

25. The shape of the extra dimensions 1 extra dimension: 2 extra dimensions: 6 extra dimensions: Many possibilities for the shape / size / topology of extra dimensions...

26. Physics from geometry

27. The Landscape of String Theory Extra dimensions dynamical: Only special shapes are stable Different possibilities for 4D physics

28. Big question: does one of these stable shapes give the physics we observe? Currently: just starting to understand the possibilities Can we make new predictions that can be tested experimentally?

29. The End of the Universe?