According to some, gravity is not a "force" at all and it is the curvature of spacetime that causes objects to necessarily follow non-euclidean paths toward the center of the earth.
We've all seen the "cannon ball on a rubber sheet" analogy to "explain" this. Problem there is, it presupposes a "force" of gravity, it seems. Why else would the cannon ball "sink into" the rubber sheet, thereby creating a depression which unsuspecting objects are forced to fall into, then follow? Without a force of gravity, why would they even "fall in" to begin with?
According to this "ask a physicist" website:
Q: Why does “curved space-time” cause gravity?
The curvature of space alone has almost no effect on the movement of objects until they are moving really fast. With the exception of only the most extreme cases (black holes), space is very, very close to flat. For example, the total stretching of space due to the Earth amounts to less than 1cm. In almost all cases the vast majority of an object’s movement is tied up in its forward movement through time.
Less than one centimeter? By the whole earth? That doesn't seem to correspond to anything like a cannonball on a rubber sheet, eh?
According to this guy, it's not the "space" part of spacetime, but rather the "time" part, which forces objects around.
How does that work, exactly? How can a completely abstract concept like "time" force objects to move? What in the world does it even mean to claim that an object has "forward movement" through time. Time is not a space, which you can move through, is it?
I don't get it.
And how does time "point?" Does it have fingers to point with, or something? This guy says:
...time pointing slightly down is entirely responsible for the motion of the planets, and every other everyday experience of gravity.
So "pointing" by "time" in the direction of "down" is ENTIRELY RESPONSIBLE for planets moving, etc., eh? Can anyone make any physical sense (as opposed to graph paper sense) out of this? If so, can you explain it to me? I don't get it, for some damn reason.
Edit: Should be obvious--I meant "gravity" in the thread title, eh?
Edited by Moronium, 10 May 2018 - 08:21 PM.