1. Announcements 4/6/11 Prayer Exam 3 ongoing Friday’s lecture: no reading assignment Project Show & Tell. Email me by Friday 5 pm. I will pick people on Friday night/Saturday morning. All late homework & extra credit papers due Fri, Apr 15. Very Important Symbols “gamma” is sometimes called “the Lorentz factor” or “the time dilation factor” Thoughts about prayer and simultaneity (or lack thereof)

2. Space-time diagrams Example: me slamming the book on the table Example: me slamming the book on the table again Example: measuring the time between book slams Example: measuring the length of the book “World lines” for Dr. Colton, book, & for space traveler passing by earth a. a.When/where do these events occur? t vs. ct

3. Quick Writing Back to Dr. Colton’s trip to Zyzyx (Dr. Colton traveling at 0.9 c). Draw, as accurately as you can, these four world-lines: a. a.The planet Earth b. b.The planet Zyzyx c. c.Dr Colton, as he travels to Zyzyx d. d.Leaving from the Earth at the same time/place, a light beam that travels to Zyzyx Draw, as accurately as possible, the same four world-lines, from Dr. Colton’s point of view.

4. Light cones Present Possible futures Possible pasts “Elsewhere” Terminology: “timelike” vs “spacelike”

5. Example Dr. Colton, on a fast train, turns on a flashlight at ct=1. People on the ground watch. Draw worldlines for Dr. Colton and the people on the ground. Draw the light from the flashlight. Mark the “flashlight turned on” event. Do this for both frames of reference.

6. Reading Quiz The Lorentz transformation equations in the book assume objects only have relative motion in the +x or –x directions a. a.True b. b.False The Lorentz transformation equations in the book given for y and z are more complicated than the equations for x and t. a. a.True b. b.False

7. Lorentz Transformations, derived Not in this class! :-) Can be done by using properties we’ve discussed: length contraction, time dilation, gamma, basic worldline transformations

8. The Lorentz Transformations As regular equations: In matrix form: Differences between my equations & book’s equations Disclaimer: I often reverse order of x and ct. That’s OK.

9. Lorentz transformations, graphically Lee’s program Similarity with rotations How to choose + vs – Note: for HW problems, you can use Lee’s program to check your answers—but not to DO your problems.