What :
Special and General Relativity: time, mass, length changes, simultanaity, speed of light as a consant, Lorentz factor, space-time diagrams, gravity as acceleration in curved space-time, black holes, cosmology

Readings :
Seven Ideas : chapter 6
Great Ideas : chapter
Conceptual Physics chapter 34 (optional)
Einstein, The Meaninf of Relativity (optional)
Thorn, Black Holes and Time Warps (optional)

Lab:
You should be working on your final project. If you haven't picked one, do so. Talk to me if you have any questions about what, why, or how.

Discussion:


1) Explain in your own words why clocks run at different rates for people moving at different speeds.

2) The cornerstone of relativity is the fact that light always moves at the same speed no matter what velocity you have. Why is this strange? Is this different from other waves, like sound? Explain.

3) Do you think that someday someone will find a way to travel faster than light? Why or why not?

4) Discuss why the word "relativity" is used to describe Einstein's theory. Exactly what is and isn't relative? Is there anything that isn'trelative?

5) If you had a rocket that could accelerate with 1g (10 m/sec2), about how long would it take you to get to 50% of the speed of light (3 108 m/sec)? (Use just ordinary mechanics formulas to answer this.)

6) And if you were in such a rocket, would you continue to travel faster if you traveled for a lot longer than this? (Say 10 times as long.) Where is the energy that your engine is expending going? What would a person on the earth see happening?

7) How fast would you need to be going to have a your clocks running half as fast as someone's on the earth?

8) What is a "black hole"? How about its "event horizon?" Might we ever make one of these in a laboratory on earth? What would we have to do? How could we tell that we had done it?

9) Explain what is meant by "the curvature of space-time" in General Relativity. What does this have to do with gravity?

Assignment 7
due Monday April 29

What :
Quantum Mechanics: Uncertainty Principle, DeBroglie Wavelength, double slit experiment, wave-particle duality, the wavefunction, probability, states, energy levels, black body spectrum, spectral lines,

Readings :
Seven Ideas : chapter 7
Great Ideas : chapter 4
Conceptual Physics part 7 (optional)
Gregory, Inventing Reality chapters 6, 7 (optional)
- There are many other popular accounts of the philosophy of QM in the library.

Lab:
The final project deadline is the last week of classes, which is coming up soon.
If you haven't started work on this project yet, then you should get going "real soon."

Discussion: (Many of these are a bit open-ended, and some of them overlap. Still, they cover the territory.)

1) What is the "uncertainty principle" in quantum mechanics? How does it work and what does it mean?

2) Describe what spectral lines are. How would you build a device to see them?

3) It is often said that within quantum mechanics, physical objects are both particles and waves. Explain this. Include a brief description of which particle and wave properties are being refered to, and include a description of experiments which give evidence for your claims.

4) Say you overhear two people discussing quantum mechanics at a cocktail party. One claims that the probability comes from the fact that we can't measure quantities precisely enough. For example, he says, the position-momentum uncertainty comes from our inability to measure both at the same time. The other says that something more fundamental is going on, and that particles don't have both of these properties at the same time. When the position is uncertain, he says, the particle really does "get fuzzy." When you join the conversation, which one would you agree with? What evidence or argument would you give to convince the other person?

5) In chemistry and other subjects, the spin of the electron is often said to be up or down. What does this mean exactly? How would measure the spin of an electron in an electron beam?

6) How can you reconcile all this bizarre quantum behavior with the macroscopic world that you see, which doesn't seem to do any of these weird things? (The "Schrodinger's Cat" paradox is a good illustration of this problem.)

7) Discuss briefly the philosophical issues behind the theory of quantum mechanics. Why has this theory, more than any other in physics, been the subject of a continuing debate as to its interpretation? Does this debate have anything to do with the experimental results themselves?