A straight line is in reality a line that is “almost” straight, or seems straight. Any line that appears to be straight can always be shown to have a slight deviation over a certain distance. Imagine a vertical line. Now mark the middle of that line with a zero. Lets assume that zero is at a point the size of an atom. Even an atom has a thickness. And let’s assume that that zero point is only 1 foot away from your eye. That thickness is enough to cause a line to curve from your eye, to that zero point, over a distance of one light year.
For this reason, my next point, I also tell people that anything you see more than 1 light year away is NOT where it appears to be.
From this knowledge (or hypothesis), we can say that all space is curved. We can say that a perfectly straight line assumes that it is aim at a perfectly zero point, and we all know, zero = nothing. And NOTHING is something that doesn’t exist (LOL).
I also Hypothesize that there is a formula for the natural curvature of light over space, but I don’t yet know how to formulate this. 🙂