Further "proofs" for the ether model.

Is there a fundamental unit of time?

Quite an intreaguing contribution to this ether model comes from a discussion forum in Scientific American: Ask the Experts: The quastion was raised by Jonathan Kent,Brooklyn, N.Y.:

Is time quantized? In other words, is there a fundamental unit of time that could not be divided into a briefer unit?

I include the full discussion here, and I will comment some of the answers at the end of this page. Additional remarks in the text are made in red.

This question is particualrly interesting, because the ether model suggests an universal clock, ticking in intervalls of 10^-23 seconds. Although the experts in the discussion forum seem to generally accept the existance (or at least not to exclude) a "time atom", they differ grossly with respect to the minimum time intervall.

One aspect should also be mentioned: Although the ether model enfavours a universal clock, this cannot be regarded as a "time atom". I have already pointed out at a previous occasion that in my opinion each universal clock pulse bears in it the complete "picture" of the whole universe. Time - as space - are continua.

John Baez is a member of the mathematics faculty at the University of California at Riverside and one of the moderators of the on-line sci.physics.research newsgroup. He responds:

"The brief answer to this question is, 'Nobody knows.' Certainly there is no experimental evidence in favor of such a minimal unit. On the other hand, there is no evidence against it, except that we have not yet found it. There are no well-worked-out physics theories incorporating a fundamental unit of time, and there are substantial obstacles to doing so in a way that is compatible with the principles of General Relativity. Recent work on a theory of quantum gravity in which gravity is represented using loops in space suggests that there might be a way to do something roughly along these lines--not involving a minimum unit of time but rather a minimum amount of area for any two-dimensional surface, a minimum volume for any three-dimensional region in space and perhaps also a minimum 'hypervolume' for any four-dimensional region of space-time."

William G. Unruh is a professor in the department of physics and astronomy at the University of British Columbia. He offers this reply:

"There is certainly no experimental evidence that time--or space for that matter--is quantized, so the question becomes one of whether there exists a theory in which time is quantized. Although researchers have considered some theories in which there is a strict quantization of time (meaning that all times are an integer multiple of some smallest unit), none that I know of has ever been seriously regarded as a viable theory of reality--at least, not by more people that the original proponent of the theory.

"One could, however, ask the question in a slightly different way. By putting together G (Newton's constant of gravity), h (Planck's constant) and c (the velocity of light), one can derive a minimum meaningful amount of time, about 10^-44 second. At this temporal scale, one would expect quantum effects to dominate gravity and hence, because Einstein's theory links gravity and time, to dominate the ordinary notion of time. In other words, for time intervals smaller than this one, the whole notion of 'time' would be expected to lose its meaning.

"The biggest obstacle to answering the question definitively is that there exists no really believable theory to describe this regime where quantum mechanics and gravity come together. Over the past 10 years, a branch of theoretical physics called string theory has held forth the greatest hope, but it is as yet far from a state where one could use it to describe the nature of time in such a brief interval."

Another, somewhat iconoclastic perspective on this question comes from William G. Tifft, a professor of astronomy at the University of Arizona:

"There are several ways to answer this question. 1) There is no conclusive evidence that time is quantized, but 2) certain theoretical studies suggest that in order to unify general relativity (gravitation) with the theories of quantum physics that describe fundamental particles and forces, it may be necessary to quantize space and perhaps time as well. (Why does he make the difference between time and space, since relativity treats time as any other space-time coordinate?) Time is always a 1-dimensional quantity in this case. 3) My own work, which combines new theoretical ideas with observations of the properties of galaxies, fundamental particles and forces, does suggest that in a certain sense time may indeed be quantized. To see this we need some background information; in this scenario, time is no longer 1-dimensional!

"My colleagues and I have observed that the 'redshifts' of galaxies seems to be quantized. The redshift is the apparent shift in the frequency of light from distant galaxies. This shift is toward the red end of the spectrum and its magnitude increases with distance. If redshifts were due to a simple stretching of light caused by the expansion of the universe, as is generally assumed, then they should take on a smooth distribution of values. In fact, I find that redshifts appear to take on discrete values, something that is not possible if they are simply due to the cosmic expansion. This finding suggests that there is something very fundamental about space and time which we have not yet discovered.

"The redshifted light we observe is consists of photons, discrete 'particles' of light energy. The energy of a photon is the product of a physical constant (Planck's constant) times the frequency of the light. Frequency is defined as the reciprocal of time, so if only certain redshifts are possible, then only certain energies are present, and hence only certain frequencies (or, equivalently, time intervals) are allowed. To the extent that redshifts of galaxies relate to the structure of time, then, it suggests an underlying quantization. (I would like to learn more about these effects. As from the arguement, it would seem that the effect should even more quantize the long radio waves as used in readio astronomy and old navigational transmitters. Since these quantisations have not been reported - and in particular the radio frequency red shifts of distant galaxies to follow the same red shifts as optical objects - the observed effect may have a slightly different reason, which might explain the following additional remarks of William G. Tifft.)

"In our newest theoretical models we have learned to predict the energies involved. We find that the times involved are always certain special multiples of the 'Planck time,' the shortest time interval consistent with modern physical theories. The model we are working with not only predicts redshifts but also permits a calculation of the mass energies of the basic fundamental particles and of the properties of the fundamental forces. The model implies that time, like space seems to be three dimensional.

We now think that three-dimensional time may be the fundamental matrix of the universe. In this view, fundamental particles and objects--up to the scale of whole galaxies--can be represented as discrete quantized structures of 3-d time embedded within a general matrix of 3-D time. The structures seem to be spraying radially outward from an origin point (time = 0): a big-bang in 3-D time. Any given chunk, say our galaxy, is flowing outward in 3-D time along its own 1-dimensional track, a 1-D timeline. Inside our (quantized) chunk we sense only ordinary 3-D space, and the single 1-dimension time flow of our chunk of 3-D time.

"Now we can finally attempt to answer the original question, whether time is quantized. The flow of time that you sense corresponds to the flow of our chunk of 3-D time through the general matrix of 3-D time. This time is probably not quantized. Both ordinary space and ordinary 'operational' time can be continuous. On the other hand, the structure of the time intervals (frequencies and energies) that make up the 3-D chunks of time which we call galaxies (or fundamental particles) does appear to be quantized in units connected to the Planck scale. In the 3-D time model, space is a local entity. Galaxies are separated in 3-D time, which we have misinterpreted as separation in space.

"What matters in 3-D time is the time intervals needed to send signals between galaxies; separation of galaxies in time, not space, is fundamental. The general matrix of 3-D time appears to contain discrete 'particles' of 3-D 'time.' These particles are the galaxies. When photons travel between galaxies, the result is a quantized structure that we see as quantized redshifts. When photons travel within a single 3-D temporal structure, we see only ordinary 3-D spatial dynamics and continuous flowing time. Believe it or not, it seems that we can have it both ways--the underlying structure of time can be 3-D and quantized, but structures in time can flow continuously."

"This intriguing question, recently considered here, has prompted additional responses and speculation. One of the new replies comes from Lawrence Sklar, a professor of philosophy at the University of Michigan at Ann Arbor:

"The idea that space might be discrete and not a continuum goes back at least as far as the ancient Greeks. Some of Zeno's arguments against the reality of motion seem to presuppose the idea of space as coming in 'units.' The idea that time was also composed of some kind of minimal elements might have occurred to them as well, although I don't know of any textual evidence for that.

"That quantum theory might require some kind of elimination of space and time as continua in favor of space and time with some kind of minimal discrete elements has certainly been suggested. At one time, but no longer, there was some hope that the famous infinite divergences of quantum-field theory might be controlled by moving to some kind of discrete space. Presumably some kind of discrete time might then have to be invoked as well. Not much came of these ideas, however.

"At present, the issue is being approached through the idea of quantizing gravity. Why? Well, in any relativistic picture both space and time are eliminated in terms of space-time. And in the theory of general relativity space-time curvature supplants the idea of a gravitational force field superimposed on a flat space-time.

"There are persuasive arguments that any consistent physics will require gravity to be quantized, although experimental evidence to that effect is nonexistent. But quantizing gravity has proved a terribly difficult problem.

"One approach is to treat gravity as another kind of force field and try to deal with it on a parallel with electromagnetism and the weak and strong interactions. Most attempts along these lines have run into insuperable problems. Another idea is to use supersymmetric string theory, which seems to have a natural place in its structure for a quantized gravity.

"More relevant, in answer to the question asked, are attempts to take the general relativistic theory of curved space-time and 'quantize' it. Doing this has proved very hard. There are two basic issues: 1) What is the theory supposed to look like? and 2) How are we supposed to 'interpret' the theory?

"In trying to understand what a quantum theory of space-time is saying, there is often the suggestion that we focus on measurement. We often think of measuring devices as detecting events. When a quantized space-time theory is so interpreted, what one hopes to get is an understanding of what kinds of probabilistic correlations among measurements will be found during a series of experiments.

"The question seems to presuppose that experiments can be performed at distinct places and distinct times; it does not presuppose the ordinary space-time continuum. But I don't know of anything going on in quantum theory of space-time that is going to suggest that the measurements will be best interpreted in a way that drops the intuitive idea of space-time as a continuum in favor of one that can be thought of as composed of discrete units."

Lee Smolin is a professor of physics in the Center for Gravitational Physics and Geometry at Pennsylvania State University. He is the author of The Life of the Cosmos (Oxford University Press and Wiedenfeld and Nickelson, 1997). He provides some further information:

"The first thing to say is that we don't know. So let me put forward some things we do know. There are various pieces of evidence that space is quantized, in the sense that there is a smallest possible unit of the area of a surface, the volume of a region or the distance between two points in space. This limit comes from applying the rules of quantum theory to Einstein's theory of general relativity. The discrete units are about the size of the Planck scale, which is 10 ^-33 centimeter, or about 20 orders of magnitude smaller than an atomic nucleus.

"There is more than one approach to combining quantum theory with general relativity that gives evidence for the quantization of spatial geometry. One of these approaches is called string theory; there are several different arguments within string theory that lead to the conclusion that space is quantized. Another line of argument derives simply from the application of quantum mechanics to general relativity. This approach was worked out first by Carlo Rovelli of the University of Pittsburgh and myself, although later many other people have confirmed this result by different methods.

"It must be mentioned that none of these predictions has so far been confirmed experimentally. But this is" just a problem of technology. It is hard to believe that there will not come a time when we can make measurements with sufficient accuracy that these predictions can be used to test the theories on which they are founded.

"Now about time: Given that both space and time are mixed up in the theory of special relativity, one might conclude that if spatial areas and volumes come in discrete units, so must intervals of time. There are indeed several approaches to quantum gravity in which space-time is discrete. Among these are proposals of Rafael Sorkin of Syracuse University, Gerard 't Hooft of Utrecht University and their colleagues. I personally find these proposals interesting and, with my colleague Fotini Markopoulou, have been studying their connection to the theories in which space turns out to be discrete. But in this case as well, the scales on which time might be discrete are tiny: 10 ^-43 of a second. At present, there is no experiment that can probe such small time intervals. What we hope to do is find out if the theory makes definite predictions regarding this question, predictions that might be tested at some time in the future.

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date of last issue: 21. 4. 1997