# Very Old Question

1. Nov 21, 2009

### sonar

What should an ancient old non-mathematical fossil do when trying to understand GR? I'm reading "Gravity" by Shutz, no problem so far, but understand I need to up my game. What do you all recommend? Note: by non-mathematical, I'm not up to speed in tensors, get most of what else there is. What's next without blowing me out of the water.
Note(2), anyone wanting to know practical knowledge of the physics of sound in water in regard to tactical usages, let me know.

2. Nov 21, 2009

### atyy

If you can read Schutz, that's good enough!

So how does one detect a dumb hole?

3. Nov 21, 2009

### sonar

I'll move from Gravity to his next one, actually gravity is interesting by not too hard.
Don't know about dumb holes, however my last boat years ago was the San Francisco which found a dumb hole (underwater mountain) off of Guam and almost sunk herself. No way sonar could hear that...

4. Nov 21, 2009

### atyy

You could also try J L Martin's "General Relativity" which I found very accessible and gets one doing calculations quickly.

Wow, so how did you get out of that dumb hole?

Some guys like Unruh are looking for dumb holes that are acoustic analogues of black holes.

5. Nov 21, 2009

### sonar

I'll give it a shot, still want to get up to tensors, that's the only way to 'understand' GR, from what I know.
The closest thing to a dumb hole, a strong negative gradient for SVP(SSP) drives sound to the bottom, active and passive sonar can't hear while in that, unless beneath the sound source, very close aboard. Not the best place to be.

6. Nov 21, 2009

### atyy

Martin's book has tensors along with the physics.

You can also try chapter 1 of Eric Poisson's "Advanced general relativity" http://www.physics.uoguelph.ca/poisson/research/notes.html which gives a summary of tensors the "old fashioned way", and Sergei Winitzki's lecture notes in which the coordinate-independent definition of tensors comes to the fore http://homepages.physik.uni-muenchen.de/~Winitzki/T7/ [Broken].

It's not much different from vectors which can be defined without coordinates (a length and a direction) or with coordinates (some matrix of numbers). The only thing to remember is that in curved space, there are no position vectors, only velocity vectors.

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