Gisin's ideas on time vs. special relativity—how does one reconcile them?

[PeroK]

Did you read Peter Insight article linked to in the first response?

Okay, everything I've said is already in there.

 

[Freixas]

Okay, everything I've said is already in there.

Ok, good. It wasn't sounding quite the same.

This is, of course, not correct at all. And highlights the problem with the over-emphasis on observers "disagreeing" about things that are simply coordinate-dependent.

The comment you were disagreeing with probably didn't mean what you thought it meant. I wasn't talking about disagreement, but about the fact that two observers at different locations cannot both verify all the same events. They don't disagree—they just don't have access to the same information.

My point about geometry and coordinate systems is that they assume a God-like view. You can seemingly confirm anything you want, totally ignoring light speed limits and thus are led down the primrose path to thinking that a block universe is the only workable model. Or at least, that was my experience.

 

[PeroK]

My point about geometry and coordinate systems is that they assume a God-like view. You can seemingly confirm anything you want, totally ignoring light speed limits and thus are led down the primrose path to thinking that a block universe is the only workable model. Or at least, that was my experience.

Does Peter's Insight not explode that myth?

 

[jbriggs444]

My point about geometry and coordinate systems is that they assume a God-like view. You can seemingly confirm anything you want, totally ignoring light speed limits

I do not see that point at all. A coordinate system is nothing more than a way of attaching numeric tuples to events. A happenstance at an event in one's causal future does not become somehow more real because there is a coordinate tuple associated with that event.

 

[PeterDonis]

My point about geometry and coordinate systems is that they assume a God-like view.

In a hypothetical scenario, yes, that's true. But that's precisely because the scenario is hypothetical. In a hypothetical scenario, the person making up the scenario can simply dictate by fiat what happens. That includes dictating by fiat what happens in the causal future of any event of interest. So the person making up the scenario does have a "God-like view" of what happens in the scenario.

In the real world, however, nobody has such a view; yet we routinely assign coordinates to hypothetical events in our causal future. For example, when the Apollo program sent astronauts to the Moon, the engineers calculated coordinates at which the spacecraft would be at future times. That doesn't mean they were assuming a "God-like view" where they knew for certain what would happen in the future--the most obvious counterexample to that claim is Apollo 13, in which the spacecraft ended up following a very different trajectory from the one that was calculated before launch. But the fact that calculations of what is expected to happen in the future are never certain does not make them useless; far from it. Apollo 13 would never have made it back to Earth if the engineers at NASA had not been able to quickly make new calculations once they knew there was a problem aboard the spacecraft .

In other words, calculations about hypothetical future events are predictions. They are constructions of a model that extends what is currently known based on the laws of physics and particular assumptions about the specific situation--for example, the assumption that the Apollo third stage is going to fire at a particular time at a particular point in low Earth orbit to boost the spacecraft towards an expected arrival at a particular point in the Moon's orbit at a particular time. And that constructed model gets built the same way all models in physics, or at least all models that are going to be used for numerical calculations, get built--using coordinates and spacetime geometry. (Strictly speaking, the Apollo calculations were non-relativistic, but that doesn't change the fundamental point.)

In short, building a model using coordinates and spacetime geometry that extends what is currently known based on certain assumptions is not the same as claiming that every single event in that model, including ones in the causal future of the event where the model is built, is fixed and certain.

 

[PeterDonis]

In a hypothetical scenario, the person making up the scenario can simply dictate by fiat what happens. That includes dictating by fiat what happens in the causal future of any event of interest. So the person making up the scenario does have a "God-like view" of what happens in the scenario.

It's worth noting that many of the arguments for the block universe (including the one I referenced in the article) can be viewed as making up a scenario, observing that you have a "God-like view" of what happens in the scenario (because you determined those events by fiat when you made up the scenario), and then incorrectly concluding that the real world must work the same way.

 

[Freixas]

Does Peter's Insight not explode that myth?

I am probably not explaining myself well. While I was pecking out an answer, Peter piped in:

It's worth noting that many of the arguments for the block universe (including the one I referenced in the article) can be viewed as making up a scenario, observing that you have a "God-like view" of what happens in the scenario (because you determined those events by fiat when you made up the scenario), and then incorrectly concluding that the real world must work the same way.

My comments were related to why people (like myself) fall into the trap of thinking that relativity = BU. Peter's comment above is a good a paraphrase of what I was trying to say.

Peter's longer post about predictions took my comments into an area I was not addressing.