Hello, fellow truth seeker, Only when space is flat do its coordinates have direct meaning of distances or angles, and if one set of coordinates have direct meaning of distances or angles then the space must be flat. This is the famous Riemann theorem when he pineered the concept of curved space. General relativists claimed curved spacetime. However, when testing GR with data, I see that all textbooks consider Schwarzschild coordinates to have direct meaning of distances or angles. Therefore, I have strong feeling that they rape common human sense. If there is no scientific conspiracy here then there must be some relativist standing out to meet my challenge!! Hello, fellow truth seeker: Could you help me find such relativists to meet my challenge here? ============================ The following is from my previous post on sciforums: On a curved space, the sum of all angles of a triangle is not \pi, either greater or less than \pi. Two famous general relativity tests are about angles. You can check whatever textbook and see that they calculate angle by directly using the coordinate \phi. They indirectly assume the domain length of \phi is 2\pi. Therfore, the sum of all angles of a triangle is \pi. That is, they assume flat space!!!!!!!!!!!!!!!!!!! Any real mathematician can tell you that all coordinate systems on a curved space are curvilinear. All coordinates are merely parameters. Real angle and distance have to be calculated by employing the coefficients of the space metric. I TELL YOU that only when the space is flat will the metric reduces to the Pythagoras theorem. That is, only when the space is flat will the coordinates have direct meaning of spatial distances and angles.