So I’m familiar with mass affecting space time, notably the grided flat sheet representing it. All objects with mass bend this sheet. The effects of massive objects are represented by the object creating wells, with the well being deeper and steeper the more massive the object is. I know this isn’t the actual explanation, but it helps visually.
I know gravity is not a force, and the reason mass “attracts” other objects is because those objects are going in the direction of the distorted space time created by the “attracting” object.
So why does mass cause a greater acceleration the more massive the attracting object is? What difference would it make if the gravity well was “shallow” or “deep”? Gravity isn’t a force, so what is actually pulling an object faster into the well depending on its depth?
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Science can aim to *describe* the nature of the universe, but when we’re aiming to describe fundamentals like forces and the shape of spacetime the descriptions feel less and less like satisfying explanations.
Before special and general relativity, the best description of reality was that objects move in straight lines unless acted upon by a force. Relativity helpfully points out that the paths of those straight lines depend on how spacetime is curved, and that this curvature depends on how energy is configured in space. If it seems weird that we don’t have a mechanism to explain what makes spacetime shaped by configurations of mass-energy, remember that we didn’t really have an explanation for the mechanism that makes objects stick to straight lines either: it just seems to be a fundamental property of the natural world.
Hopefully more study and a theory quantum gravity can shed light on whether there’s a deeper explanation for *why* spacetime’s shape is influenced by configurations of mass-energy, but even those explanations will eventually boil down to a “because that seems to be just how it works by definition” answer at some point.
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