Curved Spacetime

Curved Spacetime
(a) This flat surface represents two dimensions in spacetime. In the absence of any matter in the spacetime, straight lines are straight in our intuitive
sense (the sheet is flat). (b) In the presence of matter, spacetime curves, as shown by the curvature of the sheet when mass is laid on it. Straight
lines, defined by the paths that light rays take, are no longer straight in the “usual” sense. Besides changing the path of photons, this curvature also
creates gravity, which (c) pulls the two masses toward each other