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