Hey. I was hoping that someone(s) could give me some explanation and insight into the Penrose Diagram shown below. Any links to good sites would be great, as I have not found what I am looking for. I guess, one of the things I am really wondering is: why is there a circular like distortion in the center? But in order to understand that, I assume I would need to understand the whole premise of the idea, so.. Thanks in advance.