The mathematical basis for this kind of curved spatial geometry, restricted to only 2-dimensional curved surfaces (for example, the upper half of a sphere of fixed dimensions) in Euclidean 3-space, ...

The answer is of course 3.141592653589793..., or any number of representations in terms of infinite series. But the point of the question is that GR says we don't live in Euclidean space; we move ...

The possibility of "swimming" and "gliding" in curved, empty space shows that even after nine decades, Einstein's theory of general relativity continues to amaze In a famous series of stories in ...