Timely Mess

Is it mass that bends space-time, or is it the folds in the space-time fabric that "create" mass? Which one comes first? Far from being an expert in special and general relativity, I am fascinated by the concept of time. Can we actually think of what comes first and what comes second in relativistic terms? Is there such thing as causality when we think of time as "just" another dimension? Causality is the principle that makes us say "B happens because of A". This should imply that A happens "before" B - how else could B exist? This is because in simple human terms there is only one direction in time.

Causality has already been defined in relativistic contexts, but I still can't get my head around it. If we think that time is not such a "special" dimension, but rather an "ordinary" dimension, like length or width, then saying that A happens before B is no different than saying A is to the left/right/top/bottom/in-front-of/behind B. In other words, there would be no particular meaning to the words "before" and "after", at least no more than "top" and "bottom".

Can there be no such thing as causality? Can children exist independently from their parents? Can trees exist independently from the seeds they sprouted from? Not in our everyday experience, sure, but think about it from the perspective of an entity that moves precisely at the speed of light: for example a photon.

Time is, effectively, standing still for a ray of light. Were the photon bestowed with the gifts of sight and intellect, it would "see" the world in a very interesting way. For example, let's take my current state of "being". I am currently sitting on a double-decker London bus, going to work. I hopped on the bus about 30 minutes ago and I expect to get off it in another 15-20 minutes - traffic permitting. Imagine the route this bus takes in its hour-long journey, then take a mental snapshot of this bus and imagine that snapshot filling every point of this route. The result is a very long and flexible bus-like shape that precisely traces the entire bus route. It's a bit like the starship Enterprise when it goes warp and we see it suddenly taking this elongated shape before it enters hyperspace.

Now back to our bus. Imagine tracing this bus-like shape not only through this hour-long bus route, but through all the places this bus has ever been and will be in its working life. Looks pretty messy. If a photon came into existence the moment this very bus came into existence, that's how that photon would see this bus: a messy, fuzzy, zig-zagging bus-like shape tracing a very complex pattern that goes through all the places wher this bus has ever been and where this bus will ever be in the future.

Now imagine not only this bus, but everything else, in the same way: people on the streets, buildings and trees following the rotation of the Eearth, the planets in the solar system tracing their paths, our sun tracing its path across the galaxy, and so on. That's how a photon would see the world. Nothing comes "first" or "second" or "third": everything just "is", in a big, fuzzy, dark-brown-ish mess with no concept of causality. Why dark-brown-ish? Because of innumerable objects of different colors intersecting at innumerable different points: the more different colors you mix, the more dark and brown-ish the resulting color will be.

We just said "with no concept of causality". But is that true? After all, we still know from everyday experience that children come from parents, that trees come from seeds, and so on. There must be something that relates a "cause" with an "effect". How is that going to work when time stands still? I haven't the foggiest idea, but that is a pretty good indication that, in these terms, the definition of causality must be very different from what we are used to.