1. Physics of Time Travel

2. To the Future

3. Basic Rules for Light Light travels at a very fast speed usually denoted as c. You cannot add onto the speed of light. Someone shining a flashlight standing still: The light will go at the speed c. Someone shining a flashlight running at 10 mph. The light will still go at the speed of c.

4. Time and Light Suppose there are two people: Ann and Bob. Ann travels on very fast trains. Ann places a mirror on the ceiling and floor of the train. As the train moves, she flashes the light on the mirror and observes that the light travels back and forth from mirror to mirror. The train is traveling at the speed of c. What Ann Sees inside train

5. Time and Light Bob is standing outside of the train track with a special camera that slows down everything down. Bob records the train moving. Since, the train is made of glass, Bob can see everything inside of the train. Bob plays the tape and saw this:

6. Time and Light Speed: c Distance: 6 m Speed = distance/time C = 6 / t 4 m 3 m Speed: c Distance: 10 m (Pythagoras th) Speed = distance/time C = 10 / t If speed is the same, but the distance observed by Bob is larger than Ann. What does that tell you about time?

7. Time and Light Time is not the same for everyone or everything! Ann: c = 3 / time for Ann Bob: c = 5 / time for Bob Time for Bob is less than the time for Ann. Bobs time is moving slower than Anns time.

8. Time and Light Suppose you have an ship that can travel very close to the speed of light. If Bob and Ann are both 20. Bob stays home and Ann travels away from earth on the ship for 1 year. When Ann comes back, she will be 21, but Bob will be 27. Ann will only have to give up one year to see what will earth be like in seven years.

9. Time and Light When Bob observes Ann, time will seem slow. But for Ann and Bob, time passes on normally. One year will always feel like one year. This is not a method for living longer. In order to do this, you need to travel near the speed of light. We dont experience this since everything moves much much slower than the speed of light.

10. Video: Cosmos Time Dilation http://www.youtube.com/watch?v=6Vpu6yJP RVQ

11. To the Past

12. Grandmothers Paradox Its no impossible for something to travel to the future with the expense of a few years. However, there a lot of complications when traveling to the past. If you travel to the past and prevented your own birth, then how did you exist in the first place?

13. Alternate Universe Maybe the assumption that there are only one universe is wrong? A: Decided to travel back in time. (A world where I exist) B: Prevented my birth C: A world where I dont exist. When I go back, I will go back to branch A, where I exist. A B C

14. Wormhole There maybe holes in space in which we can travel between alternate universe.

15. Video 2: Imagining 10 th Dimension http://www.youtube.com/watch?v=JkxieS- 6WuA