English: This figure illustrates objects moving through a region of negative spacetime curvature (falling towards the Earth). The leftmost animation shows the object cluster falling, while the middle animation shows the components of the cluster moving in response to tidal forces. The world lines are plotted with position measured with respect to the blue test object (its position is treated as constant), to show tidal effects. There are two world lines that pass through point X on the spacetime diagram, and none of these intersect the worldline of the blue test object. This drawing of multiple lines that don't intersect the blue world line indicates that spacetime is negatively curved. I, the author of this image, hereby release it for use under the Creative Commons "Share Alike" license. --Christopher Thomas 01:21, 3 July 2006 (UTC)