You know, (probably soon) after I learned about spacetime, it became a mystery to me as to why we think of the universe as dynamical. You see, the present is considered to be any slice of spacetime that intersects at our here-and-now, but for a different place than here, the time of that place can vary depending on the angle of the slice: at that other place, one slice can be in the future of another slice, even if both slices intersect at our here-and-now. So, it would seem to me that the future (and the past) would be set/unchangeable, since both the future and the past of another place can be in the present of our location, depending on our velocity (that's what determines the angle of the slice). By the way, it's because velocity is relative (velocity is your direction and speed of motion in relation (relative) to another object) that any of these slices can be considered the present (if you change which object is your reference object, then your velocity is different (your velocity doesn't change, it just has a different relation to a different object, and therefore has different values when you change which object you choose to relate to), and therefore what's considered to be in your present changes, since the present is dependent on your velocity). So, as I was saying, it is an established fact that the present is variable, which means, that what's considered the present, past, or future at a place other than here, can change, so if the future can effectively become the past in some place beyond here, due merely to our actions and considerations here, then to me it would seem that the future would need to be set, based on the assumption that the past must be set. It could of course be the case that nothing other than the here-and-now is set, or that nothing outside of our past "light-cone" is set (the light cone is a double cone comprised of all the things that can affect you (your past) and all the things that you can affect (your future), so-called because it's borders are the speed of light (light can travel in all directions from you at a certain speed, and you are unable to travel faster than that speed, so your actions are confined to the volume that that light can occupy. the light forms a 4-dimensional cone: a sphere that expands as time is further from now (a 3-dimensional cone is a circle that grows in diameter as you move farther from the apex))). Another btw: that lightcone is affected and warped by the curvature of spacetime: the reason why you can't leave a black hole is because the light cone can't grow larger than the inside of a black hole, which is to say, you can't escape because light can't escape because a black hole squeezes an infinite amount of space into what, from the outside, is a finite space. Anyway, back on topic: so it could be the case that nothing exists except your past, and therefore, that your past could become something else's future due to your future actions, is irrelevant. But this troubles me, because although your lightcone is independent of your present slice (spacetime stretches and squeezes so that your light cone is the same regardless of your slice: the time axis is always perpendicular to your present slice, but not necessarily perpendicular to the slice that isn't currently yours), you are not the only object in the universe: with two objects, they could be in each other's past or future depending only on each other's relative velocities, velocities which could change. So it would seem to me, that the past and future have to be set even outside of your past lightcone, and in that case, the universe would be deterministic, i.e. there is only one future, that can't change. If the future can't be changed, and you can slice up spacetime any way you like, then it would seem to be that the universe is a solid 4-dimension object that is static, and that the reason we view time as a non-spacial direction is because entropy and (therefore) ourselves vary along its axis, and because the actions of any object with mass (such as ourselves) are forced to be closer to the time axis than to any other spacial axis (light and other massless particles are equidistant between the time axis and present slice (the present slice contains all 3 of the spacial axes)). Btw: special relativity (the velocity-dependent trade-off between space and time in a united spacetime, and the various consequences such as mass/energy equivalence) concerns the changing angle of the present slice and time axis, and the resultant squeezing and stretching of time and space (the angle-changing/squeezing&stretching being relative to other slices and axes), while general relativity (the curvature of spacetime in response to energy, causing accelerations we call gravity) concerns the shape of the time axis and present slice themselves, and consequently the shape of the light cone (leading to scenarios such as the future cone not being able to extend beyond the interior of a back hole if the here is within the event horizon). Again back to the matter at hand (there is a lot of diversions, but they are necessary to understanding the subject matter): so, while technically only your past cone is set in stone, there exist more objects than you, so my thought process concludes, that since where another object lies on your time axis is variable, and that object can be taken as a focus just as much as you can be, then therefore all activities along any time axes must be preset. And therefore, with the universe being deterministic, the time axis can be treated like a spacial axis with extra properties, and thus we can consider the universe as a static 4-dimensional object, rather than as a dynamic 3-dimensional object. So what's the difference, if these two objects are physically the same (they are both our universe)? There's a conceptual difference: when we talk of spacetime curvature, we usually talk about it curving in response to energy: we talk about time being affected, when time is the medium of affects: it's nonsensical. Sure, the Higgs field interacts with itself (higgs interacts with higgs), but time is the medium of interaction itself (interaction interacting): the analogy would instead be that mass itself gains or loses mass, not that all areas or objects gain mass, but that mass(noun) masses(verb). It's hard to describe because it's that ridiculous. And so it is with time, causation itself, being subject to causes. When the Higgs field interacts with itself, it is interacting in a medium external to itself, that medium being spacetime. Now, you could propose dimensions external to the universe, but that wouldn't address what the curvature of spacetime actually is: it's not some amount of energy at a particular point within spacetime acting on that spacetime to form a contraction or expansion of spacetime at that point in spacetime, it's an amount of energy at a particular point within spacetime with a corresponding smallness or largeness of spacetime at that point in spacetime: the energy does not produce the curvature (in its future), the curvature is where the energy is (in its present). There is no delay to curvature: the curvature is not a millisecond up the time axis from the energy, it's at the energy; the curvature isn't caused by the energy, it is with the energy, having the same location as the energy; it corresponds. Where there is energy, there is curvature, not there will be curvature. So, in my view, the universe is a 4-dimensional static object, with bumps where there is energy, and which, for some reason, one of the dimensions imposes constraints: the world-line of a particle (the trajectory of the particle through spacetime) can not be farther from this axis than the other axes, and the universe is larger in the other axes as you move in one direction along the special axis, and smaller as you move in the opposite direction. So, framing it this way, why is it that universe is constrained around one of its 4 axes? Why does it have directionality instead of simply being a blob? This is what we do not know, but I think we would be more likely to find out if we used this framing. As to why spacetime has a correspondence between its shape and its energy, I would argue, that its shape is the energy: to speak of one is to speak of the other. What do you think of all of this?