- #106
belliott4488
- 662
- 1
starkind:
If I tried to respond to all that you've written here, it would probably take an entire forum page. More importantly, it would almost certainly take this thread even farther from its original topic than it already is. For that reason, I'd like to respond in detail directly to you and to post only a general high-level response here. If the details of our conversation are interesting to others, then I suggest that we start another thread to continue it there.
I don't seem to have made my point very clearly, so let me try again. First, the distinction between "physical space" and "mathematical space" is yours; I don't believe I made it, but if I did, then I was possibly being a little sloppy. I meant to distinguish between different mathematical spaces, all of which are abstract by definition, and all of which correspond to various physically measurable quantities.
Physics is the business of creating mathematical models of physical observables with a well-defined correspondence between the observables and the entities in the mathematical theory. One possible set of observables is that of spatial measurements, such as relative position. We can model this set with a 1-d mathematical space, perhaps to describe the position of a bead on a wire; a 2-d space, as we regularly do with street maps; a 3-d space, as we do for all sorts of problems in classical mechanics; or a 4-d space if we're doing relativistic mechanics. These spaces are all abstract, but they correspond to physical observables, specifically to relative positions.
There are also other physical observables that can be modeled by other mathematical spaces. Those abstract spaces also have various properties, which might well correspond to relationships between the physical observables being modeled. An example is momentum space, which is often used to model classical mechanics. It's no more or less real than position space, but you shouldn't confuse the two because points, or coordinates, in each of these spaces correspond to different (and incompatible) physical observables.
When we talk about the symmetry groups of fundamental particles, those groups have representations, which may well be described by geometry. The points in this space do not correspond to points in position space, however; they correspond to particle states. Just because, for example, an up quark might appear to the left of a down quark in a particular visualization of the group, that has nothing to do with where it is in position space, and therefore has nothing to do with where we might measure its position (assuming we could even do that).
My point boils down to this: the mathematical model has parts that correspond to positions in space and parts that don't. The root space that we've all seen in Lisi's E(8) theory has geometric properties, but they do not correspond to geometric properties of relative positions of particles.
If I tried to respond to all that you've written here, it would probably take an entire forum page. More importantly, it would almost certainly take this thread even farther from its original topic than it already is. For that reason, I'd like to respond in detail directly to you and to post only a general high-level response here. If the details of our conversation are interesting to others, then I suggest that we start another thread to continue it there.
I don't seem to have made my point very clearly, so let me try again. First, the distinction between "physical space" and "mathematical space" is yours; I don't believe I made it, but if I did, then I was possibly being a little sloppy. I meant to distinguish between different mathematical spaces, all of which are abstract by definition, and all of which correspond to various physically measurable quantities.
Physics is the business of creating mathematical models of physical observables with a well-defined correspondence between the observables and the entities in the mathematical theory. One possible set of observables is that of spatial measurements, such as relative position. We can model this set with a 1-d mathematical space, perhaps to describe the position of a bead on a wire; a 2-d space, as we regularly do with street maps; a 3-d space, as we do for all sorts of problems in classical mechanics; or a 4-d space if we're doing relativistic mechanics. These spaces are all abstract, but they correspond to physical observables, specifically to relative positions.
There are also other physical observables that can be modeled by other mathematical spaces. Those abstract spaces also have various properties, which might well correspond to relationships between the physical observables being modeled. An example is momentum space, which is often used to model classical mechanics. It's no more or less real than position space, but you shouldn't confuse the two because points, or coordinates, in each of these spaces correspond to different (and incompatible) physical observables.
When we talk about the symmetry groups of fundamental particles, those groups have representations, which may well be described by geometry. The points in this space do not correspond to points in position space, however; they correspond to particle states. Just because, for example, an up quark might appear to the left of a down quark in a particular visualization of the group, that has nothing to do with where it is in position space, and therefore has nothing to do with where we might measure its position (assuming we could even do that).
My point boils down to this: the mathematical model has parts that correspond to positions in space and parts that don't. The root space that we've all seen in Lisi's E(8) theory has geometric properties, but they do not correspond to geometric properties of relative positions of particles.
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