Hello, :) The below link has great examples and simple explanations of 4D space-time light cone diagrams and how they are used in Special Relativity. http://www.phy.syr.edu/courses/modules/LIGHTCONE/LightClock/default.html The university site above was very helpful for visualising how special relativity is graphed. It’s all good, But does any expert or enthusiast of General Relativity know of any sites that show decent visual examples and straight forward explanations of a Gauss or Gaussian co-ordinate systems? The short book I’m reading on G.R. refers to Gauss co-ordinates but does not show any good examples of what the Gauss co-ordinate graphics look like in full. I did do a search for images of gauss co-ordinates but came up with very little. I must not be using the best key words. Thanks in advance for any helpful links. Very best Eon.