pduff%ti-eg.csnet@csnet-relay.arpa (08/14/85)
From: Patrick_Duff <pduff%ti-eg.csnet@csnet-relay.arpa> In place of some of the stupid questions that have recently been discussed, I'll pose some (perhaps equally stupid) questions: From time to time I hear or read about speculations that the values of the fundamental constants *could* be different now than they were 10**n years ago (given a suitably large value of n, as long as it is after the big bang plus one minute). Is this complete idiocy, or do some physicists take the possibility seriously? What about speculations that the values of the fundamental constants *could* be different in another part of the universe? There seem to be two possibilites, either that there is a continuous, gradual change, or that there is an abrupt change at "domain walls" separating various regions of the universe. The claim is made that we could not detect such variations since all of our measurements of distant phenomena are made locally, and hence are subject to transformations due to local conditions. Should these speculations be ignored, or do they have some merit? Accepting for the moment that the value of one of the fundamental constants (pick one!) could be changed, would it vary independently of the others or would some of the other constants change too? What are the relationships between the so-called "fundamental" constants, if any? Which of them seem to have unconstrained and hence "arbitrary" values? Has anyone heard more concerning the formulation of gravity as a push from infinity (analogous to the pressure inside a balloon) which is attenuated by mass instead of its more common formulation as a pull between masses? Last I heard there wasn't a way to distinguish between the two possibilities via experimentation, since all of the various experiments which researchers came up with would give the same results either way. If the push from infinity formulation is correct, then it seems to me that adding or removing mass from the universe would change the gravitational constant everywhere in the universe, though I'm not sure whether adding mass would increase it (more pressure) or decrease it (more attenuation). I've heard that there may only be one electron in the whole universe, which explains why all of the electrons we observe have exactly the same charge and mass. Does anyone understand how one gets the observed universe which appears to have *lots* of electrons from just one particle? What about the two electron spin states, and positrons (just one anti-electron in the whole universe?)? Or is the one-electron theory full of holes (sorry about that--I couldn't resist!)? regards, Patrick Patrick S. Duff, ***CR 5621*** pduff.ti-eg@csnet-relay 5049 Walker Dr. #91103 214/480-1659 (work) The Colony, TX 75056-1120 214/370-5363 (home) (a suburb of Dallas, TX)
gwyn@BRL.ARPA (08/14/85)
From: Doug Gwyn (VLD/VMB) <gwyn@BRL.ARPA> (1) Change in values of "fundamental constants" over time. (2) Change in values of "fundamental constants" over the universe. These are related issues since space and time are interrelated. The real question is, what is meant by "fundamental constant"? If this means anything, it must mean a quantity whose numerical value is not arbitrary; otherwise it would be an accidental parameter of a specific configuration of the universe and thus would not be truly "fundamental". So what qualifies as a fundamental constant? At the current state of knowledge, there seem to be two categories of such constants. The first and simplest consists of pure (unitless) numbers, such as the fine-structure constant. The second consists of everything else believed to be intrinsic properties of the physical world. Such "constants" as the speed of light, density of water at STP, Planck's constant, and Newton's gravitational factor are not numerically constant at all, but depend on the units of measurement. However, to the extent that they measure something inherently real (as opposed to conventional), they qualify as fundamental physical constants. Because they are constrained by reality, their values are constrained to change in definite ways when the system of units is changed. By generalizing from this observation, one arrives at invariance groups and the tensor calculus. Now, because physics is more than (space-time) pointwise local, to compare events at one point of space-time with events at another, some "transport mechanism" is required to carry the quantities determined at one such event to another so that the two sets of quantities can be compared. Such a mechanism is known (the "affine connection" field), and Einstein's general theory of relativity is based on it. (Actually, the first formulation of general relativity did not use such a general viewpoint, but Levi-Civita, Weyl, and others developed the transport-mechanism viewpoint to such a degree that it is now the natural way to formulate relativistic field theory.) The full development of the purely affine theory leads to much more than just a theory of gravitation; I did a Master's thesis on this very subject. So, if physical quantities are going to vary over the space-time manifold, they're going to have to follow quite definite known rules of behavior. Of course, pure numerical (unitless) physical constants cannot vary from point to point if they measure something truly fundamental. Several famous theoreticians have gotten quite interested in deriving the values of such pure numbers. The names of Dirac and Eddington spring to mind in this connection. (3) How are the fundamental constants related? Well, the speed of light is just a conversion factor between space and time units, which were separate for historical reasons. Minkowski seems to have been the first to appreciate this point. The Newtonian gravitational constant relates units of energy (or mass) to those of space-time, according to the source-free formulation of general relativity. Various other presumably-fundamental constants can be combined to produce pure numbers; the "fine-structure" constant (roughly 1/137) is the most famous such pure number. It is not currently known whether such pure numbers measure local conditions or universal conditions; this is the same question as above. (4) Gravity as a "push" instead of a "pull". The best theory of gravitation (general relativity or its nonzero-torsion generalization) is not expressed in terms of attraction or repulsion. Therefore I find this question uninteresting. (5) Only one electron in the whole universe. This sounds like an idea attributed to Feynman and Wheeler. The idea is that a positron can be considered an electron going backward in time. If one thinks solely in terms of particle collisions in space-time, it becomes possible to propose that there is only one electron/positron trajectory zigzagging back and forth in time to produce all the electrons and positrons that we observe. The only real advantage to this theory is that it definitely accounts for the observation that all electrons have identical fundamental characteristics such as charge and rest mass. However, I am not at all fond of infinite-particle theories and think that a pure field theory is conceptually much cleaner (presumably, if the QCD type of theory is any good, it is exactly equivalent to a pure field theory -- if only we could magically perform all the Feynman integrals). The main drawback to a pure field theory is that it is not known to be able to explain quantization, but there are certainly some unexplored possibilities in that direction. (One of them is the question I asked some weeks back on this list, to which no one responded.)
markb@sdcrdcf.UUCP (Mark Biggar) (08/16/85)
In article <495@sri-arpa.ARPA> pduff%ti-eg.csnet@csnet-relay.arpa writes: > I've heard that there may only be one electron in the whole universe, >which explains why all of the electrons we observe have exactly the same >charge and mass. Does anyone understand how one gets the observed universe >which appears to have *lots* of electrons from just one particle? What >about the two electron spin states, and positrons (just one anti-electron >in the whole universe?)? Or is the one-electron theory full of holes >(sorry about that--I couldn't resist!)? It Goes like this: It has been suggested that an anti-particle is just a normal particle going backwards in time. For example if you show a movie of an electron curving in a magnetic field backward it would lokk just like a movie of a positron in the same field going forward. Thus there is only one electron looping through time so we see it many times. Mark Biggar {allegra,burdvax,cbosgd,hplabs,ihnp4,akgua,sdcsvax}!sdcrdcf!markb
tmb@talcott.UUCP (Thomas M. Breuel) (08/18/85)
In article <495@sri-arpa.ARPA>, pduff%ti-eg.csnet@csnet-relay.arpa writes: > From time to time I hear or read about speculations that the values of > the fundamental constants *could* be different now than they were 10**n > years ago (given a suitably large value of n, as long as it is after the > big bang plus one minute). Is this complete idiocy, or do some physicists > take the possibility seriously? Yes, some physicists do. Several 'fundamental constants' may be tied to the size of the universe as a whole, most notably the gravitational constant. > What about speculations that the values of the fundamental constants > *could* be different in another part of the universe? There seem to be It is possible that certain fundamental constants are tied to quantities like space curvature or (to name something far-fetched) neutrino density in some not yet understood manner. Of course, the term 'fundamental constant' would be a rather dubious description of those quantities if either spatial or temporal variation occurred, and a theory describin their behaviour would probably suggest suitable re-placement constants. > Accepting for the moment that the value of one of the fundamental > constants (pick one!) could be changed, would it vary independently of the > others or would some of the other constants change too? What are the Who knows. Since we don't know where fundamental constants come from, since there is no theory predicting them, there is no way of answering that question (and indeed the question is wrong if fundamental constants are really constants). I am sure, though, that if you ask ten different professors of physics they will give you ten different answers about possible relationships among fundamental constants. > Has anyone heard more concerning the formulation of gravity as a push > from infinity (analogous to the pressure inside a balloon) which is > attenuated by mass instead of its more common formulation as a pull between > masses? Last I heard there wasn't a way to distinguish between the two If there is no way of distinguishing between the two theories, then they are really one and the same theory. What the effect of adding or removing mass from the universe is on the gravitational constant in either theory is open to speculation (and definitely not open to experiment). > I've heard that there may only be one electron in the whole universe, > which explains why all of the electrons we observe have exactly the same > charge and mass. Does anyone understand how one gets the observed universe > which appears to have *lots* of electrons from just one particle? What That is only a question of definition. Except for spin, all electrons seem to be identical. Therefore, if you detect an interaction with an electron at some point in space, you cannot tell which electron it is. Therefore, you might as well take all the 'electron clouds' in the universe together, and call the resulting probability distribution of interaction with an electron 'the' electron. For practical (or rather theoretical) purposes this makes absolutely no difference, since when you work out the behaviour of a system, you assume it to be in complete isolation anyhow, i.e. you take into consideration only those parts of the system that are really necessary to give you a reasonable answer. > Or is the one-electron theory full of holes > (sorry about that--I couldn't resist!)? It is not a theory, it is merely a matter of definition. It seems to be just the kind of thing that many people like to quibble about fruitlessly for long times, without, of course, coming to a solution. It falls into the same category as the multiple worlds interpretation of QM. Thomas.
mikes%orville@sri-unix.ARPA (08/19/85)
From: mikes@orville (Peter Mikes)
I recall the idea of "one elctron/positron" zig-zagging the spacetime
as being attributed to Dirac. It is indeed possible to dream up many ex-
planation s which do not have experimental implications - that's why the
Occam razor - properly used - is necessary.
Doug, could you please restate your question about unexplored possibilities
of explaining quantization in QCD ? It mussed have been buried somewhere
- I do not recall noticing it.
john@frog.UUCP (John Woods) (08/20/85)
> In place of some of the stupid questions that have recently been > discussed, I'll pose some (perhaps equally stupid) questions: > Your questions were refreshing non-stupid! > > From time to time I hear or read about speculations that the values of > the fundamental constants *could* be different now than they were 10**n > years ago (given a suitably large value of n, as long as it is after the > big bang plus one minute). Is this complete idiocy, or do some physicists > take the possibility seriously? > Many physicists take this question quite seriously. However, it turns out that they are fairly confident that (at least several) constants have been constant for at least several million years: they found this natural nuclear reactor in France, a deposit of uranium ore in spongy rock. Every time it rains, the water acts as a moderator, and spontaneous fission happens. By now, the deposit is fairly well depleted of fissile uranium, but by analyzing the abundances of various isotopes present, they have determined that this thing has been going, more or less constantly, for (I think) several hundred million years. Why is this interesting? The absorption of a slow neutron by U-235 is the result of a resonance effect (which overcomes the normal tendancy of the neutron to just bounce off), and this resonance is somewhat of a chance conspiracy of (in effect) several of the fundamental constants, which determine the eigenstates of the U-235 nucleus. These functions that determine these eigenstates are very sensitive to changes in these "constants", and it turns out that if the constants were much different at all, U-235 would not be fissionable. However, this pile of U-235 has been fissioning constantly for hundreds of millions of years, placing the maximum rate of change at something incredibly low (assuming of course that the values did not change incredibly suddently microseconds before the molten rock cooled). > What about speculations that the values of the fundamental constants > *could* be different in another part of the universe? There seem to be > two possibilites, either that there is a continuous, gradual change, or that > there is an abrupt change at "domain walls" separating various regions of > the universe. The claim is made that we could not detect such variations > since all of our measurements of distant phenomena are made locally, and > hence are subject to transformations due to local conditions. Should these > speculations be ignored, or do they have some merit? > These speculations do have merit, but (I believe) most physicists adopt the hypothesis that everything is the same everywhere because (1) it is easy, (2) it makes it possible to get work done, and (3) what few subtle clues they can obtain without going out there indicate that the assumption is reasonable. > Accepting for the moment that the value of one of the fundamental > constants (pick one!) could be changed, would it vary independently of the > others or would some of the other constants change too? What are the > relationships between the so-called "fundamental" constants, if any? Which > of them seem to have unconstrained and hence "arbitrary" values? > I don't know. My guess is that, since "fundamental constants" are an artifact of explanation rather than root causes, whatever happens to change one of them might or might not change others. > Has anyone heard more concerning the formulation of gravity as a push > from infinity (analogous to the pressure inside a balloon) which is > attenuated by mass instead of its more common formulation as a pull between > masses? > I haven't heard of this one. > I've heard that there may only be one electron in the whole universe, > which explains why all of the electrons we observe have exactly the same > charge and mass. Does anyone understand how one gets the observed universe > which appears to have *lots* of electrons from just one particle? What > about the two electron spin states, and positrons (just one anti-electron > in the whole universe?)? Or is the one-electron theory full of holes > (sorry about that--I couldn't resist!)? > As a guess, this sounds more like someone couldn't handle the idea of postulating something distateful (a humongous number of indistinguishable things) and postulated something complicated (poor, busy electron!). I rather take the view that electrons are just explanations -- perhaps there are little critters running around "down there", but they appear to be rather perverse creatures--hence I try to avoid ascribing "common-sense" attributes to them. If you prefer, I avoid insanity by going quietly mad... :-) -- John Woods, Charles River Data Systems, Framingham MA, (617) 626-1101 ...!decvax!frog!john, ...!mit-eddie!jfw, jfw%mit-ccc@MIT-XX.ARPA