The discussion revolves around the nature of spacetime orientation within the context of relativistic field theory, specifically questioning whether spatial and temporal orientation is a convention or not. It explores concepts of orientation in Minkowski spacetime, the implications of coordinate independence, and the relationship between mathematical representations and physical reality.
Participants express differing views on whether spacetime orientation is a convention, with some asserting it is while others maintain that physical objects and processes have a non-conventional orientation. The discussion remains unresolved with multiple competing perspectives.
There are unresolved nuances regarding the definitions of orientation and convention, as well as the implications of mathematical representations versus physical reality. The discussion also highlights the complexity of distinguishing between different types of orientations in various contexts.
My point was that you need a reference, which you can choose by convention. An objective one, transportable to any place and valid at any time, according to the HEP Standard Model, is the left-handedness (right-handedness) of neutrinos (anti-neutrinos). Then you can define of any (chiral) object which orientation it has relative to the so defined properties "left" and "right". That's indeed independent of the choice of coordinates.PeterDonis said:Yes, but the fact that one cannot be continuously transformed into the other is not. So there are two orientations, which we can label however we want, and given any physical object, we can check which orientation it can be continuously transformed into and which one it can't. The result of this check is independent of any coordinate choice or any choice of labeling of orientations; that is the sense in which a physical object has an orientation that is not a convention. (The only complication here is that some objects, for example a perfect sphere, will not have an orientation in this sense.)
vanhees71 said:you need a reference, which you can choose by convention
vanhees71 said:An objective one, transportable to any place and valid at any time, according to the HEP Standard Model, is the left-handedness (right-handedness) of neutrinos (anti-neutrinos)