From: SMTP%"PSYCHE-D@IRIS.RFMH.ORG" 16-OCT-1996 19:52:00.17
To: STAPP
CC:
Subj: Re: "now"
Approved-By: PATRICKW@CS.MONASH.EDU.AU
Approved-By: STAPP@THEORM.LBL.GOV
Message-ID: <961015123637.346004b7@theorm.lbl.gov>
Date: Tue, 15 Oct 1996 12:36:37 -0700
Reply-To: PSYCHE Discussion Forum
Sender: PSYCHE Discussion Forum
From: Henry Stapp
Subject: Re: "now"
To: Multiple recipients of list PSYCHE-D
Comment on Pat Hayes's posting to Psyche-d about "now".
About "now", I agree with Pat that the idea of "the present now" is pretty
incomprehensible within the "standard" picture, where one just adds a
fourth dimension to the three spatial dimensions. This simple addition of
time to the spatial dimensions is sometimes called the spatialization of time,
and although Einstein himself generally avoided making ontological commitments
he is sometimes credited with believing that this mathematical step is somehow
closely connected to ontology. I think this attribution is merely on the
basis of a letter of condolence to the widow of a colleague: the letter
suggested that "now" was an illusion.
But in his scientific writings Einstein was more cautious. His theory of
relativity was formulated in terms of a realm of "readings of clocks and
rulers", that could be conceived to be a vast realm of abstract "readings",
some of which could be equated to what appropriately situated and endowed
human observers could sense or perceive. His theory was essentially a
mathematical desciption of relationships that extended over all of spacetime
of these readings on different *sets* of clocks and rulers that were organized
in different ways into different coordinate systems. He thus cleverly avoided
getting entangled with the issue of the ontological "now", while preserving
everything that scientists needed to do science, within the framework of
classical mechanics. The key point here is that classical mechanics is
deterministic, and hence specifies in terms of initial conditions the entire
spacetime description, so that there was no concept of "becoming" within the
theory: everything was, from the theoretical point of view, all laid out. And
within his realm of readings everything was also all laid out. Yet each
possible observation was labelled by readings on rulers that identified "where
the observation was occurring, as specified in different coordinate systems,
and "when" it occurred, as specified by the clocks coordinated to the various
coordinate systems. So the ontological issues were neatly side-stepped,
in favor of connections among observables.
Pat indicated that one advantage of quantum mechanics was that it provided a
place for "the present now". I agree. The point is the within the collapse
interpretations there are really two different notions of "time". This is most
clearly seen in the so-called "Heisenberg picture". In this representation of
the theory, which is the best for rigorous work, the "operators" of the
theory, which are the quantum analogues of the "values" of, say, the
classical local fields, are assigned to spacetime points. Thus, just as in
classical mechanics, one writes the electric field as E(x,t). The fields over
all spacetime are fixed *once and for all* by deterministic equations of motion.
The time t that appears here in close conjunction with the spatial variable
x (a three component vector) can be called Einstein Time, because it is the
time of relativistic spacetime. But the "state vector" evolves in a different
time, which can be called Process Time: if there were no collapses then
there would be no evolution in Process Time; the state vector would be
constant. In the Bohr/Heisenberg/vonN/Wigner formulation of quantum that I
have been defending it is evolution in Process Time that corresponds to the
advancing "now" that we experience.
I am happy to be in apparent agreement with Pat on this matter.
Henry P. Stapp