The discussion revolves around the question of whether the one-way speed of light is constant and independent of position. Participants explore the implications of this concept within the framework of special relativity, addressing both theoretical and experimental aspects.
Participants express differing views on the constancy of the one-way speed of light, with some supporting the idea as a useful convention and others questioning its validity. The discussion remains unresolved with multiple competing perspectives presented.
The discussion highlights the dependence of the one-way speed of light on synchronization conventions and the implications of different coordinate systems, which are not fully resolved.
It is a postulate of special relativity that the one way speed of light is constant (although it takes a bit of care to state the postulate precisely). Theories based on other assumptions can be constructed, but all that are consistent with observations are more complicated, require other assumptions that are less palatable, and make no testable predictions that special relativity does not. Thus there are no good reasons not to proceed as if the one-way speed of light is constant.CompSci said:Is there any reason to believe that the one way speed of light is constant? Not isotropic, but constant in the sense of being independent of position.
The term for that is homogeneous. Usually “constant” refers to being independent of time.CompSci said:Summary:: Is the one way speed of light constant?
Not isotropic, but constant in the sense of being independent of position.
Einstein essentially defined it to be constant, homogeneous, isotropic, and frame invariant. You can define it other ways if you like - it turns out to be just a matter of choosing a non-trivial coordinate system. An obvious example is a rotating coordinate system, where the coordinate speed of light varies with radius.CompSci said:Summary:: Is the one way speed of light constant?
Is there any reason to believe that the one way speed of light is constant? Not isotropic, but constant in the sense of being independent of position.
CompSci said:Is there any reason to believe that the one way speed of light is constant?
The only consequences are to coordinate systems. Not to observation or experiment.Mister T said:But it's an assumption that has consequences.
jbriggs444 said:The only consequences are to coordinate systems. Not to observation or experiment.
Nonetheless, it’s an an important consequence - relativity is by far the cleanest and most elegant formulation of the physics.Mister T said:Ah, yes. Of course. Because it depends on a simultaneity convention.