socrat44 wrote:You didn't explain why >> "Invariant" is a completely different phenomenon than "stationary"... a, practically speaking, opposite meaning.
In SR "invariant" is the opposite of "relative". hyksos was alluding to the fact that "stationary" (i.e. "at rest" is a relative term. This is fairly basic. as other forms of "relativity" were known long before SR. What makes SR valuable is that it offers other "invariant" quantities as well (for example, spacetime intervals, speed limit c & the mass-energy of a particle in its rest frame).
If you are in deep space and see an asteroid approaching steadily, SR asserts there is no distinction between you moving toward the "resting" asteroid, the asteroid moving toward "resting" you or some combination of motions. "Rest" and "stationary" are relative terms in SR as are all constant velocities. The most that can be asserted is that they are not accelerating (changing speed or direction).
bangstrom wrote:a simultaneous flash of light somewhere along the “space” axis
...
another possibility where separation in space always includes a c related separation in time so we never have separation of space without an observed separation in time “spacetime.”
"Simultaneous" implies "without separation in time". There's a conflict if you both assert and deny separation in time.
bangstrom wrote:This makes the “spacelike” part of chart unobservable and probably nonexistent
"Unobservable" Yes, by someone at a distance from that location. But different observers can observe different locations simultaneously, so we can be confident those locations do exist. Besides, essentially all observations involve some sort of time delay. No one is surprised by this. Observation by lightlike interaction gives an invariant (i.e. agreeable) delay.
bangstrom wrote:The remote end of an entangled spin state may be depicted as occurring on the horizontal, spatial coordinate
Correct.
bangstrom wrote:an energy exchange by entanglement
No such thing! The entanglement connection is non-traversable by mass, energy or information. It mainly serves as a correlation reference for shared quantum states. You are correct to surmise that communicating a verification of a change in quantum state is limited to speed c. But the actual change in quantum state (e.g. from entangled to disentangled) has no such limit.
bangstrom wrote:I see no reason to interpret the slope of the "communication" coordinate as a speed rather than a time/space dimensional constant and I prefer the latter. Largely because it appears as an absolute
I don't think you'll get in any major trouble with that. Keep in mind that particle accelerators push those little buggers very, very, very, very, very close to c and you would agree that those are actual "speeds".