2.13, 3.1

I'm making posts really early, 'cause I'll be gone all weekend...

This section felt a lot like 2.11, there was a good bit of algebra to derive some wave behavior. I understood it better than 2.11 though. I was kind of curious about Love waves - is it possible to give a quick hand-wavy explanation of them like you did with the Raleigh waves (which, I think, did help in understanding the section)? On a more practical note, I'm a little bit curious about what happens around the depth where the retrograde motion turns into prograde motion. It seems like there might be some interesting phenomena there, once some of the terms cancel out and we can see the effects of things we'd neglected elsewhere, but I'm not really sure.

3.1

Phew, I think I'm getting better at understanding this tensor algebra stuff! It's getting quicker to read these types of sections, though it still takes some time to get through it all. One part that I wasn't able to figure out though was the note about 'effective pressure'. It seemed like a silly trick that didn't give me anything useful; did I miss something, is there some physical meaning to it that's good to know or some way in which it needs to be used?

2.13

This section was a good bit shorter! I'm very happy with it - we defined a conservation of energy law, which is cool. I didn't really have any issues with this section, I thought it was reasonable and made sense to me. I'll still have to go back over the previous section to make sense of all the derivations though.

2.11

Oof! This section dove into more detailed algebra than the previous ones... or is it just me? I'll probably have to read over some of those derivations again, and I'll probably grasp some of this better once I start doing the homework and get more of a handle on it. I was a bit curious about the potentials though. In electrostatics/electrodynamics, the potentials actually do have interesting physical interpretations. Are there physical interpretations for these potentials, phi and A? They're certainly interesting mathematical tricks to make the equations more solvable, but it would be even better if they had some sort of interpretation on their own as well.

2.8-2.9

I thought these sections were pretty interesting, but I wasn't sure of the use of the quasistatic approximation. We use it to be able to talk about path-independent quantities and then to justify more symmetries. However, it seems like motion in which there is no acceleration isn't too interesting, since it excludes wave phenomena and all sorts of other things. I'm having a little bit of trouble following through on where we need the quasistatic approximation and when we don't, and whether we'll need to keep in mind that some of the things we derive aren't valid when acceleration is present.

It's cool how we now have a potential energy function. That seems like it'll be very important, and adds a lot to my understanding of the system.

2.10

Wow, section 2.10 was really cool! I don't really have any particular questions about it, I thought it made sense, but I thought it was really cool how we can take nonlinear equations, identify when they're "almost linear", and rewrite them in a form that's probably way easier to solve.

Section 2.7

Section 2.7 is comparatively short, but I'm not completely clear on how the symmetries in the elastic constants play out. Sure, I can write them out and convince myself that there's 36 of them, but is there some better way of seeing how symmetries reduce the number of degrees of freedom of a tensor?

Sections 2.4-2.6

The derivation of the use of ellipsoids to visualize the tensor fields is interesting, but I'm having a lot of trouble figuring out how I would ever read one, or how to handle the hyperbola case. Are we going to use this more, and if so, are there some nice easy examples for me to look at so I can try to figure it out?

I got the explanation of why the stress tensor had to be symmetric, that made a lot of sense and was neat.