Spaces may have positive curvature (+1) zero curvature (0) or negative curvature (-1). In other words, this has the structure of a game.
For instance, a Euclidean space has zero curvature. This space has an n-dimensional quadratic metric which is Pythagorean, defined by
a circle. We have defined other conic sections in the Mathematics part of this website, in the book Numbers, equations and proofs.
Gravitation is a type of force present in spaces of positive curvature. Antigravity is, at least theoretically, a property of spaces of
negative curvature. You will see below that the Casimir force, which is not explicitly gravitational in origin, but a property of the
quantum 'vacuum' (or ether) is also dependent on the curvature of the plates between it. The Casimir effect is attractive for plates with
a positive curvature, and negative for plates where their mutual close interface has negative curvature, defined as a type of 'saddle'
Eric Laithwaite Youtube
Long wave (47 times diameter of Earth) gravitational detectors
The Landau-Lifshitz pseudotensor
The Casimir effect
The BOOMERanG experiment