Dieu,
I've been taking potshots at the notion of spacetime as well. The point I make is as to why time is included as a dimension with space in the first place. As individual beings, we experience change as a singular sequence of events and so perceive this effect call 'time' of the present moment 'moving' from past to future events. This is the basis for the idea of history and thus human civilization, so it is a profound view. Newton considered time to be an absolute flow, but the problem evident by Einstein's time is that there is no way to measure an absolute flow of time. That in fact the same or similar clocks will record different rates under different conditions. So much of the dilemma leading up to the theory of relativity was how to explain this variability of the passage of time.
The point I keep making is that time is not the present moving from past to future, in some larger four dimensional reality, but the changing configuration of what exists, which turns future into past. For example, the earth isn't moving/existing along some fourth dimension, or universal flow, from yesterday to tomorrow. rather tomorrow becomes yesterday because the earth turns.
This makes time, as change, an effect of action. There is only this activity in space, the contraction of mass and expansion of radiation, with time as a measure of the change it creates. This makes time similar to temperature, not space. Time is to temperature what frequency is to amplitude. We think of temperature as a cumulative effect of many actions, yet that is exactly what we find, but cannot figure out about time. There are lots of things changing, yet we cannot find how to measure the overall rate. There is just this dynamic reality with lots of things moving about and it creates an overall effect and the only overall measure would be a cumulative average, just like with temperature.
It also resolves the issue of determinism vs. probability. When we treat time as that passage from a determined past into a probabilistic future, some think it must mean the future is already determined, since the laws only yield a singular outcome. Then some think the past remains probabilistic and must create alternate realities with every possibility, in a multiworlds situation.
Now if we view it from the other direction, the process by which events happen and thus future probability becomes past actuality, it makes much more sense. The laws may be deterministic, but the total input into any event only occurs with the event, so the occurrence of the event is what determines it.
Gravity then emerges as the opposite effect of radiation and thus is a cumulative contraction of energy into mass, rather than just a property of mass. They can't find that dark matter on the perimeter of galaxies, but they do find lots of cosmic rays and other properties on that border between light and matter. What galaxies do not radiate away as light, they shoot out the poles as cosmic jets and then eventually this all cools enough to start coalescing again. Convection is what we call this expansion/contraction cycle, here in the surface of this world.
Regards,
John M