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The problem is that there is no change or any notion of time flow in physical models. They describe a static 4-D universe. So there is no particle but there is

The problem is that there is no change or any notion of time flow in physical models. They describe a static 4-D universe. So there is no particle but there is a one-dimensional world line in the equations with no difference between points. Surely time has a particular property that is reflected in the equations that one can predict across time and not space. The notion of that world line reflects this. But this does not tell why we perceive those world lines point by point. I.e. a physical model is like a set of frames for a movie with particular relations between frames. But it does not tell why if we see the movie we perceive the motion and not, for example the whole movie at once. Or why the perception is across time and not space. And since these being discussed in various forms since at least Parmenides and Buddha I doubt this will be resolved any time soon.

tsimionescu 5y ago
> The problem is that there is no change or any notion of time flow in physical models. What do you mean by this? When I write x(t) = x0 + (dx/dt) * t + (d2x/d2t) * t^2, time is right there in the equation. In relativity, it is even self-evidently different from the 3 spatial dimensions: s = sqrt(x^2 + y^2 + z^2 - (ct)^2). There is even a somewhat intuitive interpretation for the special-ness of the time dimension: all matter is constantly moving along the ct axis of space time at speed c, unless acted on by some force, trying to follow the shortest distance between the past and the future (so the trajectory bends towards the center of mass of any other matter it finds on the way).
- fpoling 5y ago
  That equation describes a curve in 2 dimensional space with no differences between points with each point having particular time and space coordinates. And you can even resolve it to express time as a function of space. But we do not interpret that as a flow of space.
  - tsimionescu 5y ago
    Sure, but you still can't explain it without adding an extra dimension to your model, and that extra dimension is not symmetrical with the space dimensions. In fact, there is no physical model that I am aware of that makes time and any space dimension interchangeable. The fact that our mathematical models generally seem to allow movement backwards and forwards in time is in stark opposition to observed physics. This obviously suggests that the models are wrong, and there is something about time we are not capturing well enough. Relativity does somewhat fix this, by essentially postulating that everything is moving with speed c in space-time, but that is a somewhat unsatisfying explanation, since it seems natural to ask why.
    - fpoling 5y ago
      The extra dimension does not explain the movement or change. The world line corresponding to the equation is static. It does not show at all why when one looks at a particle, one perceive the movement and change in the position, and not, for example, the whole world line at once. I am not saying that time and space are the same in physical equations. The point is that they do not describe the perception of time flow, not that there is no difference between time and space. As I wrote the structure of equations (equations are parabolic or hyperbolic, not elliptical, the sign of the time dimension in the metric tensor is opposite to the space coordinates) reflects that one can predict across time but not space. I.e. the equations reflects that from a picture of a room one can tell what will happen in one hour or what did happen one hour ago. Shadows from the Sun will move, a sleeping cat will not be there, but things will be mostly the same. But try to tell what is in the rest of the room from a one-hour long video of the wall. It is not possible. But this difference tells nothing about perception of “now” or the time flow. In a sense the equations reflects how memory operates. We remember a sequence of events and we can focus on a particular moment or select events in an arbitrary order similar how we can select a point or points on the world line of a particle. But the memory does not have “now” and so the equations reflecting the notion of the world line tell nothing about the time flow.
      - tsimionescu 5y ago
        Apologies, only now do I really get your point.

tsimionescu 5y ago

> The problem is that there is no change or any notion of time flow in physical models. What do you mean by this? When I write x(t) = x0 + (dx/dt) * t + (d2x/d2t) * t^2, time is right there in the equation. In relativity, it is even self-evidently different from the 3 spatial dimensions: s = sqrt(x^2 + y^2 + z^2 - (ct)^2). There is even a somewhat intuitive interpretation for the special-ness of the time dimension: all matter is constantly moving along the ct axis of space time at speed c, unless acted on by some force, trying to follow the shortest distance between the past and the future (so the trajectory bends towards the center of mass of any other matter it finds on the way).

fpoling 5y ago
That equation describes a curve in 2 dimensional space with no differences between points with each point having particular time and space coordinates. And you can even resolve it to express time as a function of space. But we do not interpret that as a flow of space.
- tsimionescu 5y ago
  Sure, but you still can't explain it without adding an extra dimension to your model, and that extra dimension is not symmetrical with the space dimensions. In fact, there is no physical model that I am aware of that makes time and any space dimension interchangeable. The fact that our mathematical models generally seem to allow movement backwards and forwards in time is in stark opposition to observed physics. This obviously suggests that the models are wrong, and there is something about time we are not capturing well enough. Relativity does somewhat fix this, by essentially postulating that everything is moving with speed c in space-time, but that is a somewhat unsatisfying explanation, since it seems natural to ask why.
  - fpoling 5y ago
    The extra dimension does not explain the movement or change. The world line corresponding to the equation is static. It does not show at all why when one looks at a particle, one perceive the movement and change in the position, and not, for example, the whole world line at once. I am not saying that time and space are the same in physical equations. The point is that they do not describe the perception of time flow, not that there is no difference between time and space. As I wrote the structure of equations (equations are parabolic or hyperbolic, not elliptical, the sign of the time dimension in the metric tensor is opposite to the space coordinates) reflects that one can predict across time but not space. I.e. the equations reflects that from a picture of a room one can tell what will happen in one hour or what did happen one hour ago. Shadows from the Sun will move, a sleeping cat will not be there, but things will be mostly the same. But try to tell what is in the rest of the room from a one-hour long video of the wall. It is not possible. But this difference tells nothing about perception of “now” or the time flow. In a sense the equations reflects how memory operates. We remember a sequence of events and we can focus on a particular moment or select events in an arbitrary order similar how we can select a point or points on the world line of a particle. But the memory does not have “now” and so the equations reflecting the notion of the world line tell nothing about the time flow.
    - tsimionescu 5y ago
      Apologies, only now do I really get your point.