Kerr Ring

Factual Questions
1

I was flipping through a wired magazine the other day (I think it’s the current issue) and they had an article on time travel that I thought was interesting.
There were several methods mentioned, but one stood out: It was the Kerr Ring; which is basically (if I understood it right) a supercompressed object the mass of jupiter, compressed to a 5 foot sphere (or so) and then set spinning. This is supposed to be a time machine, giving you access to any point in history-the catch is, you can never come back.

Why can’t you come back? Also, can someone explain “Kerr Rings” to me in dumbspeak (hehe, you know, layman’s terms and what not)?
(I’ve googled it, but the pages I’ve found seem to be technical like this one.)

2

Going by this page, a “Kerr Ring” (theorised in 1963 by New Zealand mathematician Roy Kerr), is actually a black hole that, because of spin, doesn’t collapse to a point, but a “ring of fire”, through which a wormhole might form leading to a parallel universe.