# Reduced Circumference

1. Jun 14, 2005

### Moore1879

Okay, I understand that the r-coordinate in the Schwarzschild metric represents the reduce circumference. My problem is that the r-coordinate in the Kerr metric is NOT the reduced circumference! What is it? Somebody, please answer this as quickly and as painlessly as possible!
Thank You

2. Jun 21, 2005

### hellfire

Right, it is not. What is it? Sorry, I don’t know... I guess that if you make a coordinate change in a way that you get $$\inline{R(r)^2 d{\phi}^2}$$ then $$\inline{R}$$ will be the reduced circumference for $$\inline{\phi}}$$. May be this can give you a hint about a possible physical meaning of $$\inline{r}$$.