1. Modern Physics April 30, 2009

2. Motion is Relative Frame of Reference - perspective from which you observe

3. Special Theory of Relativity (1905) – describes how time is affected by motion and how mass and energy are related

4. 1 st Postulate = Observers cannot detect their uniform motion, except relative to other objects.

5. 2 nd Postulate = The speed of light, c, is constant and is the same for all observers.

8. Time Dilation Video Clip http://www.walter- fendt.de/ph14e/timedilation.htm http://www.pbs.org/wgbh/nova/einstein/hotsc iencetwin/index.html

9. Time dilation = time stretches or slows as an observer approaches the speed of light Moving clocks run slow

10. Twin Trip Video on Laser Disc or DVD

11. Time dilation equation Moving Time Proper Time

12. Time dilation simplified Time onboard the spaceship Time on earth % of the speed of light

13. Example) Superman leaves Lois in Metropolis to rescue a spaceship. Flying at a speed of 0.70c, Superman reaches the ship in 20 hours according to his wristwatch. How long did the trip take according to Lois’ clock on Earth?

14. What happens if you could go faster than the speed of light? Some say it is impossible Time simply stops at c Maybe time reverses - time travel? Maybe you can see the past but not interact

15. Work on front side Special Relativity Worksheet

16. Time Machine