A Unlearning Block Universe: BU vs Presentism Q&A

[GrayGhost]

OK, so I was reading thru a prior thread UNLEARNING THE BLOCK UNIVERSE, initiated by user Lynch101, and which has already been locked by the forum. There were many good responses. It was stated that PRESENTISM and the BLOCK UNIVERSE are 2 philosophical interpretations of the very same LTs, and so they are indistinguishable by test.

The LTs require the time desynchronisation of moving bodies, per the inertial stationary observer moving relatively. Consider a starship moving inertially at relativistic rate. Per the Block Universe interpretation, for clocks synchronised in the starship, its foward clocks lag the time readout of its aftward clocks. This is to say that each position of the starship (along it's axis of motion) exists in a different starship era of time, per the stationary POV in his own instant of time, and this is consistent (of course) with the past, present, and future all coexisting on equal footing in a fused spacetime contunuum.

OK, so I'm hoping a relativity mentor or science advisor will chime in here, on this one question ...

Q) How is the time desynchronisation of moving bodies explained by the PRESENTIST interpretation?

Thank You,
GrayGhost

 

[Halc]

The LTs require the time desynchronisation of moving bodies, per the inertial stationary observer moving relatively. Consider a starship moving inertially at relativistic rate. Per the Block Universe interpretation, for clocks synchronised in the starship, its foward clocks lag the time readout of its aftward clocks.

That interpretation says no such thing. If the clocks are synced in the ship frame, then they are synced in that frame and not other ones. All frames are equally valid under block interpretation.

It is the presentist interpretation that posits only one objective way to sync the clocks, and no way for the people on the ship to determine how to do this.

Q) How is the time desynchronisation of moving bodies explained by the PRESENTIST interpretation?

Clock moves fast (an absolute thing, not relative), so it is dilated. It's that simple. A stationary clock runs at full speed, if at zero gravitational potential, which of course nothing is. That's another thing nobody seems to be able to measure is what is the (absolute) average gravitational potential here on Earth.

 

[Ibix]

Q) How is the time desynchronisation of moving bodies explained by the PRESENTIST interpretation?

One frame is, in some sense, the right one. Clocks synchronised in this frame are synchronised in the now that actually exists. All others aren't. But causality in relativity doesn't depend at all on the definition of "now". It depends on what is (or was, in this interpretation) in your past light cone and sent some kind of signal that is affecting you now, and what's in your past light cone is the same in any interpretation. Thus this choice of "real" frame is indetectable and irrelevant.

 

[GrayGhost]

That interpretation says no such thing. If the clocks are synced in the ship frame, then they are synced in that frame and not other ones. All frames are equally valid under block interpretation.

Very sorry Halc, but I really have no idea why you would post this in relation to my question.

Brest regards,
GrayGhost

 

[PeterDonis]

I really have no idea why you would post this in relation to my question.

It was a perfectly valid response to this erroneous statement of yours:

Per the Block Universe interpretation, for clocks synchronised in the starship, its foward clocks lag the time readout of its aftward clocks.

 

[GrayGhost]

OK, so Ibx seemed to understand my question. I thought the follow-on sentence amplified it enough, however I'll reword the OP below to make it clearer.

Ibx, thanks for the response. That's the way I've always understood it as well, ie the Presentist interpretation requires a preferred frame behold of TRUE simultaneity, and frames moving relatively do not. Before I respond further, I'll take a little time to work on a more detailed scenario, to be more specific. I'm focusing on what time desynchronization "means" (per Presentism) as it pertains to moving bodies, per the observer not of the preferred frame.

Here's my OP rewrite ...

********

OK, so I was reading thru a prior thread UNLEARNING THE BLOCK UNIVERSE, initiated by user Lynch101, and which has already been locked by the forum. There were many good responses. It was stated that PRESENTISM and the BLOCK UNIVERSE are 2 philosophical interpretations of the very same LTs, and so they are indistinguishable by test.

The LTs require the time desynchronisation of moving bodies, per the inertial observer moving relatively. Consider a starship moving inertially at relativistic rate. Per the Block Universe interpretation, given starship clocks are all synchronized in the starship's own frame, its foward clocks lag the time readout of its aftward clocks per a relatively moving observer ... which is to say that each position of the starship (along it's axis of motion) exists in a different starship era of time, per said moving observer. This is consistent (of course) with the past, present, and future all coexisting on equal footing in a fused spacetime contunuum.

OK, so I'm hoping a relativity mentor or science advisor will chime in here, on this one question ...

Q) How is the time desynchronisation of moving bodies explained by the PRESENTIST interpretation?

********

Thank You,
GrayGhost

 

[Nugatory]

Q) How is the time desynchronisation of moving bodies explained by the PRESENTIST interpretation?

If you choose a definition of “at the same time“ such that the hands of the clocks are all at the same position at the same time then the clocks are all synchronized. Choose a different definition of “at the same time” and they wI’ll be desynchronized.

This will be true whether you use the block universe model or not.

 

[Nugatory]

The only reason this thread can be tolerated under the forum rules about not arguing over block universe and LET is that it’s correcting OP’s misunderstanding.

that’s done, so the thread is closed.
(as with all thread closures, PM me or any other mentor if you want it reopened to add additional explanation)