Comments on Soul Physics: How Special Relativity Thwarts Eternalism (And Mor...

Nice post, Bryan. It reminds me of Einstein's ...

2010-12-24T21:29:00.562-05:00

Nice post, Bryan. It reminds me of Einstein's Galilean relativistic dream, tweeked a bit.

Imagine three cowbells, tuned to notes A, B, and C, hung a hundred feet apart in a straight line in the order A-B-C;
Einstein stands in the middle and presses a button to simultaneously send an electrical signal through three equal length electric wires to sound the bells simultaneously.
Assistant at A records the sequence ABC,
Assistant at C records the sequence CBA,
Einstein records B followed by an AC chord.
Each of these three observations is repeatable and factual, yet contradicts the other two. All three event sequences are simultaneously true!
Therefore, one must conclude that:
1) All events are relative to space-time locality
2) There are an infinite number of objectively inconsistent histories of the world, each originating in its here-now.

Steve Gabor

Bryan, it seems this extra assumption ends up bein...

2008-07-16T13:12:00.000-04:00

Bryan, it seems this extra assumption ends up being problematic since it confuses what all observers would agree upon ontologically with what they'd agree upon epistemologically. That is you are in effect saying that epistemology (what they can measure) entails the ontology. I don't think everyone would agree.

Of course this ends up being a problem with uses of SR against presentism since the epistemology vs. realism issue is key. And the skeptic can always point to the epistemological issues.

Richard: you've got the idea, and your objection i...

2008-07-14T16:58:00.000-04:00

Richard: you've got the idea, and your objection is well taken. My argument does depend on this claim:

(*) The only factual properties of spacetime are those that are agreed upon by all observers.

An objector could consistently discharge that assumption, and indeed avoid my conclusion. However, I claim that physics in practice assumes (*). For example:

(1) The existence of an electric field depends on the motion of an observer, as in the famous example of a conductor around a magnet. 19th century ether-theorists assumed that there was one correct observer (namely, the ether rest-frame), and thus a fact of the matter about the field's existence. But the 20th century saw the wide adoption of (*), and thus the rejection of the electric field by itself as an objective property of spacetime.

(2) More recently, QFT-interpreters have noticed that Unruh radiation consists in particles that exist for accelerating observers (like Alice), but not for inertial observers (like Bob). My assumption (*) is often explicitly adopted to argue that "particle number" is not a fundamental property in QFT (for example, see Wald 1994, pp.116).

Rather than list more examples, let me concede that (*) might still be wrong. In this case, I am willing to fall back to a more modest claim: Special Relativity together with modern physics practice thwarts eternalism.

Thanks for the note! -Bryan

Just to check I've understood the argument in part...

2008-07-14T13:05:00.000-04:00

Just to check I've understood the argument in part III correctly: there's a frame of reference (namely, Alice's) according to which some events (those in regions I or II) are not simultaneous with any moment whatsoever, and therefore not determinate/real. Is that it?

But why does it matter if "there are observers who disagree about whether or not e is determinate"? You earlier talk about how a property must be "in principle accessible by some observer". So why not stick with that, and say that an event is determinate/real so long as it fits within some frame of reference or other? Why require all? That stricter requirement seems unmotivated to me. Alice should simply recognize that there are blocks of spacetime which are inaccessible, in terms of simultaneity planes, from her frame of reference.

Justin: yes, you won't want to confuse those two c...

2008-07-14T03:21:00.000-04:00

Justin: yes, you won't want to confuse those two concepts. Here's the difference.

Determinism is a mathematical property, which is (or is not) possessed by a theory. (Earman (1986) for more.)

Determinateness is a (vague, Platonic) property that some suggest is possessed by the world.

Here's a way to pull the two ideas apart. In order to ask whether or not determinism holds, you will typically need an equation of motion and an initial state. If these two ingredients guarantee a unique way that the initial state can evolve in the future and past (a unique path through phase-space), the this system is deterministic.

Notice that there is no question yet about what's real and what isn't. This was a question about the uniqueness of solutions to a differential equation.

You don't need any of that mathy stuff to talk about determinateness. In fact, you can (presumably) ask if an empty universe with no dynamical field equations has determinate spacetime points. The reason is, determinateness is supposed to be a question about what is real and what isn't at various points in time and space. And I argue that the very idea is whacky.

Hope that helps! -B.

I'm a bit confused--how does determinateness relat...

2008-07-14T00:12:00.000-04:00

I'm a bit confused--how does determinateness relation to the notion of being determined (or determinism)?