Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!lll-crg!dual!qantel!hplabs!sri-unix!mikes@AMES-NAS.ARPA From: mikes@AMES-NAS.ARPA Newsgroups: net.physics Subject: Re: Heisenberg Uncertainty Principle Message-ID: <492@sri-arpa.ARPA> Date: Mon, 12-Aug-85 17:18:21 EDT Article-I.D.: sri-arpa.492 Posted: Mon Aug 12 17:18:21 1985 Date-Received: Sat, 17-Aug-85 06:03:43 EDT Lines: 63 From: mikes@AMES-NAS.ARPA (Peter Mikes) Subject: Re: Heisenberg Uncertainty Principle In-Reply-To: Article(s) <3506@decwrl.UUCP> > Is it strictly a case of the measurement process itself disturbing the > individual particle, or is something else going on there? Can we > find a measurement process that uses small enough particles so that they > won't disturb the particles we are trying to measure? But you can't! gwyn@brl-tgr.ARPA (Doug Gwyn) I would like to prefix my comment to the above by few disclaimers: 1) the opinions are mine, not my employers, his clients etc etc 2) my opinions on QM are unorthodox - but I hope not in conflict with known facts (or even future one's) 3) I agree, in this case (and others) with Gwyn : "You cant" in both accepted and other interpretations of the Quantum Noise, BUT I think that the fact that "there is no measurement process possible" which would determine p&q DOES NOT (necessarily) implies that 'it is strictly a measurement process itself, disturbing the particles..' . Actually I believe that Heisenberg analysis of different measurement setups is secondary and accidental. There is something called the "fluctuations of the vacuum' which has nothing to do with measurement process. There is an 'intristic pressure' of the electron gas, which can be measured (as high pressure limit of conven- tional materials) and which can be calculated from the Uncertainity Principle. There is no measurement involved! This 'quantum pressure' is as real as an osmotic pressure in gas is real - neither is dependent on what WE know about the system. Once you accept the 'existence' of this disturbance, the Uncertain- ty Principle follows naturally as a special case. I consider the typical textbook presentation of Heisenbergs Principle AS CAUSE of the quantum rand- mness as a half-truth which cannot survive a critical analysis. In other words 'even if you could determine p&q at the same time ( some believe that that is a meanigless statement) I believe that you would not be able to make exact predictions - just knowing the MACROSCOPIC potential and those exact initial conditions.' We all agree, I think, that Gwyn:"This is a matter of fundamental principle, not of insufficient cleverness on the part of the measurer." ...that you cannot measure both p&q. The difference of opinion is subtle and easy to be overlooked. The key, once again is the Einstein's definition of what is ' a complete description of reality'. Later developments (Bell's uneqality and Aspects experiments) did not invalidated his remarkably logical definition, they just confirmed that it is indeed a fundamental principle that 'you cant' discover 'hidden parameters' which a clever experimenter can go after to circumvent Heisen- bergs principle. Accepting both Einstein's definition and Bell's analysis, it seems to me that 1) there is both p and q - 2) There is no way we can determine both. That in itself may be disturbing (that are things which WE cannot know) but it's not impossible (actually - it rather natural). The real issue - which I hope somebody will respond to is this: Bells ana- lysis killed the 'Hidden Parameter Theories'. OK - do the concepts of the 'field' (these are related but non-identical concepts: Bohm's/Fenyes's Quantum potential, DeBroglies Pilot Wave, and this concept of the Quantum Fluctuations, taken outside of the context of QED) which is influencing the microscopic particle, which is moving according to the Schrodingers eq. qualify as Hidden Parameters? I do not see how - and I am eager to learn. Peter M.