# Bei's Study Notes

### General Relativity 06Last updated: 2016-08-14 19:21:06 PDT.

Reference: UCI OpenCourseWare - GR 07 (Playlist)

### Some remarks (Mach's Principle)

Starting from 39:00.

My Note: I've never been convinced of Mach's Principle. In fact, there has been many null results in testing Mach's principle. I don't know this has to be a thing in the first place.

### Non-Cartitian coordinate system

Starting from 1:07:55.

Starting from an example:

We will try to calculate the metric in this case. The Jacobian:

The inverse is simple:

The important takeaway is that is in fact not a tensor, for that it can be in some coordinate systems but non-zero in others, even in the same planar space.