On the Impossibility of Time Travel by J. C. N. Smith

Essay Abstract

Intended to offer a fresh look at a venerable chestnut of speculation, the essay describes why time travel of the variety portrayed in science fiction is not possible, and, in so doing, offers thoughts about time which are intended to shed light on its fundamental nature.

Author Bio

J. C. N. Smith is retired from the CIA's former Office of Scientific and Weapons Research. Reading, thinking, and occasionally writing about issues related to time have been his avocation and passion for more than 40 years, with specific aims being to gain a deeper understanding of the universe and its workings and to peel away misperceptions which may be impeding advances in modern physics. He has published several monographs on the nature of time.

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Thank you for your comments. Have you read Julian Barbour's book 'The End of Time'? If not, I highly recommend it. He addresses issues relevant to those you've raised. Definitely worth exploring.

In his book 'The Trouble With Physics,' Lee Smolin wrote, "More and more, I have the feeling that quantum theory and general relativity are both deeply wrong about the nature of time. It is not enough to combine them. There is a deeper problem, perhaps going back to the origin of physics." (page 256) This is precisely the point which I make, explicitly, in reference 4 to my current essay. See http://googlepages.com/time . This is why I believe we must question the validity of notions such as "space-time bending back on itself." That may be true IF you accept the conventional concept of time, but it is exactly this conventional concept which I believe we must re-examine and re-think.

Mr. Huffman,

Thank you for your comment! You raise a good point! And I have what I believe is a good reply to the point you raise. There is more to my proposed definition of a particular time than first meets the eye. Although I did not think it was appropriate to address all the ramifications of the proposed definition in this essay, I did address some of them in reference 4 to the essay. The proposed definition leads directly to logical conclusions which do lend themselves to falsification! Please see http://smithjcn.googlepages.com/time Thank you!

The theme of the current essay cmpetition concerns what is or is not possible in physics. The additional information to be found in my referenced essay does not bear directly on this theme, and hence I chose not to address it here. You could be correct to question the wisdom of that decision.

Of course another obvious way to falsify the assertion of my current essay would be to demonstrate that someone has in fact accomplished time travel of the variety portrayed in science fiction! Thanks again for your comments.

Mr. Johnstone,

Thank you for your comments, which certainly are on target. I'm currently about three quarters through the process of very carefully re-reading Barbour's 'The End of Time,' and would like to withhold a direct reply to your points until I've completed this review. My views of time are something on the order of 98 percent aligned with Barbour's on most issues, but I am yet to be convinced of his claim that the universe is static. His description of what he calls the Machian distinguished simplifier in Chapter 7 seems to offer a way to explain dynamic phenomena without recourse to the notions of absolute space and time. This hope later appears to be dashed, however, in Chapter 17.

One very quick comment on your observations regarding relativity: Barbour correctly points out (on page 137 of The End of Time) that, "Relativity is not about an abstract concept of time at all: it is about physical devices called clocks. Once we grasp that, many difficulties fall away."

If you like the approach taken in my current essay, I'd urge you to read my reference 4, which offers a slightly different approach to the broader topic of time. As noted elsewhere in these posts, that essay does not address any implications for time travel, per se, so in the interest of staying on topic for this competition, I did not allude to some of the interesting (to me at any rate) ramifications of this approach to time which are addressed there.

I'll try to offer a better response to your comments after completing my review of The End of Time.

Mr. Johnstone,

Having now finally completed my re-reading of Julian Barbour's 'The End of Time,' (TEOT) I will do my best to comment on the excellent points you raised.

As noted in my previous post, my thinking is closely aligned with Barbour's on many points. Where I part company with his thinking is on the major and crucial subject of motion. He argues that the universe is static. I maintain that motion is real. Which brings us to the point you raised: how can we describe motion in a three-dimensional universe without recourse to some additional dimension? I believe that Barbour offers a path to accomplishing this in his Chapter 7, in which he describes his collaboration with Bruno Bertotti to lay out a genuine Machian theory of the universe.

If there is motion, as I maintain, then how do we describe the 'trajectory' of the universe from one configuration to another without recourse to an absolute time and space? On page 120 of TEOT, in describing what he has called the "Machian distinguished simplifier," Barbour writes, "When this distinguished simplifier is used as 'time', it turns out that each object in the universe moves in the Machian framework described above exactly as Newton's laws prescribe. Newton's laws and his framework both arise from a single law of the universe that does not presuppose them. In such a universe, the ultimate standard of time that determines which curve is traced by Galileo's ball when it falls off his table in Padua is unambiguous. It is the average of all the changes in the universe that defines the Machian distinguished simplifier. Time is change, nothing more, nothing less." The goal, as I see it, is to have a dynamics which describes how the three-dimensional universe moves from one configuration to another without requiring the a separate dimension for time.

Barbour writes (p. 69), "Of course, to say that time has passed, we must have some evidence for that. Something must move. That is the most primitive fact of all." Of course, I fully concur with that view. But I do not take the point for granted. Another "primitive" fact which misled us for centuries was the apparent rising and setting of the sun; this, like the concept of motion, was something we could literally see with our own eyes. And yet it was fooling us into holding a faulty perception of the universe. Could our perception of motion be simply another trick of nature? Perhaps, but I do not think so. We corrected our faulty perception of what it meant to observe the sun apparently rising and setting when we obtained more information and a better perspective in the form of empirical, astronomical observations. I do not foresee that happening with our perception of the reality of motion.

As to the point you raise about the "twins paradox," I would simply reiterate my previous comment, echoing Barbour, that relativity deals with the behavior of mechanical devices which we call clocks. I concur totally with his comment (page 107) that ". . . there is only one ultimate clock: the universe." The twins must be put into this larger perspective to see what happens with them and with their clocks, relative to the bigger clock of the universe.

Now, I must admit that I was somewhat shocked, for lack of a better term, to re-discover a brief section in the epilogue of TEOT which deals specifically with the possibility of time travel! How could I have forgotten it? The answer to this question is, I regret to say, that his discussion of the topic is, sadly, in my opinion, quite forgettable. It is almost as though Barbour does not believe in the reality of his own theory of time! He states (p. 68), "What is the reality of the universe? It is that in any instant the objects in it have some relative arrangement." This is precisely my view! Barbour's "instants" or "Nows" clearly correspond with what I call "particular times." But whereas I see these relative arrangements of all the objects in the universe in a literal, real, naive, primitive sense, Barbour seems to see them as being abstract, mathematical concepts, just one of many possible hypothetical configurations in his relative configuration space of Platonia.

I sometimes have the impression that Barbour and I are looking at the universe and at the concept of time as though we were looking at a Necker Cube, an optical illusion in which it is possible to look at the same physical picture and arrive at two different interpretations of reality.

I hope this at least partly addresses the points you raised.

Mr. Johnstone,

Thank you for your thought-provoking comments, questions, and good wishes. I hardly know where to begin a reply, but perhaps a broad comment on my own background would be helpful to put things into perspective. First, I am not a professional physicist; I am a layman who likes to imagine himself as following in the footsteps of a long and honorable, but perhaps vanishing, line of what once were known as "citizen scientists." I mention this by way of responding to your question about whether I've read Barbour's papers or seen his mathematical formalism for deriving the "best matched" configurations. Let me say that I have looked at the papers which he has kindly made available on his website, but I will not pretend that I have been able to follow all the mathematics presented in the papers. This might explain why citizen scientists are a vanishing breed; science is becoming so specialized and complicated that few amateurs can truly master its intricacies.

My perspective on these topics is more qualitative than quantitative, a perspective which I hope may include a few advantages along with its obvious disadvantages. There is no risk of my being led astray by pursuing the siren song of elegant mathematics purely for its own sake, for example. I rely heavily, but not exclusively, on popularizations such as 'The End of Time,' 'The Trouble With Physics,' etc., to stay abreast of current thinking. Which reminds me that TEOT is now already a decade old. Perhaps we're about due for an update?

As to your question about why the Kingfisher has wings if there is no motion, that is indeed an excellent question. And why do we have legs, arms, and opposable thumbs? The argument for a static universe apparently is summarized thusly, "A classical theory that treats time in a Machian manner can allow the universe only one value of its energy. But then its quantum theory is singular - it can only have one energy eigenvalue. Since quantum dynamics of necessity has more than one energy eigenvalue, quantum dynamics of the universe is impossible. There can only be quantum statics. It's as simple as that!" (p. 253, TEOT) This is a case in which I fear we perhaps are being led astray by either the theory or the math or an unholy combination of both. On balance, I believe the evidence in favor of motion is stronger than the evidence against it.

Regarding your thought experiment involving a "global boost" in the form of a uniform change of scale, it appears that Barbour is toying with just such an idea even now. See his 'Dynamics of pure shape' under the heading Ideas at his website. Not having given it a great deal of thought, my first question would deal with gravity. Assuming the masses of objects do not change, and if we can consider them as point masses, then if we double all the distances between them wouldn't the attractive force of gravity be reduced by a factor of four? Wouldn't that be measurable? Or perhaps I'm missing your real point?

As to whether it would constitute a change of configuration in Barbour's scenario, you are raising some tough questions! These are questions probably best posed to Mr. Barbour himself. My first thought is that it would depend on whether or not any measurable effect resulted from the change. If we truly had no way of knowing a change of scale had occurred, then according to Leibnitz's principle of the identity of indiscernibles, if two things are identical in all their attributes, then they are actually one. If a change has no measurable effect, how can we call it a change? But again, I may be missing your point.

I hope some day we will have good answers to all these questions, but it probably will not happen tonight; the hour is late, and I fear that my brain is rapidly turning to mush.

Cheers!

.

Mr. Johnstone,

I welcome the idea of keeping the lines of communication open. I don't know off hand whether FQXi offers a more private "back channel" for communicating email addresses or other personal information. If not, it might be a feature they should consider adding; other forums to which I've posted have offered this convenience.

In the meantime, this forum will serve well enough, so long as we stay more or less on topic. Like you, I am immersing myself in reading (actually mostly re-reading) several popular books which address our topic. I'm currently enjoying a re-visiting of Smolin's 'The Life of the Cosmos,' and will follow that with a re-read of his 'The Trouble With Physics.'

The latter book includes the following extremely enticing sentence: "More and more, I have the feeling that quantum theory and general relativity are both deeply wrong about the nature of time. It is not enough to combine them. There is a deeper problem, perhaps going back to the origin of physics." (p.256) This just happens to be precisely the point I have tried to make, very explicitly, in reference 4 to my current essay. And I proceed there to offer what I hope may be a first baby step toward correcting that early misdirection.

Another book which I would highly recommend, in case you've not already read it, is David Deutsch's 'The Fabric of Reality,' a key idea from which is, " . . . scientific discovery need not begin with observational evidence. But it does always begin with a problem. By a 'problem' I do not necessarily mean a practical emergency, or a source of anxiety. I just mean a set of ideas that seems inadequate and worth trying to improve." (p. 62) This, to my way of thinking, is an apt description of "the problem of time."

Elsewhere, Deutsch continues, "Given a shred of a theory, or rather, shreds of several rival theories, the evidence is available out there to enable us to distinguish between them. Anyone can search for it, find it, and improve upon it if they take the trouble. They do not need authorization, or initiation, or holy texts. They need only be looking in the right way - with fertile problems and promising theories in mind." (p. 94)

Now, from my own experience, I would add one caveat to Deutsch's comment: should a "better explanation" be discovered and proposed by someone from outside the mainstream of science, it is not always the easiest thing in the world for such a person to find a forum in which to present his or her ideas. That, in a nutshell, is the beauty of an open competition such as these made possible by FQXi. The competition offers a level playing field for ideas in much the same way as those offered in "open" competitions in sports such as tennis or golf.

Back on topic, when Copernicus and Kepler offered a profoundly new way of explaining our perception that the sun moves around the earth from east to west (an "obvious fact" which even a child can observe), their ideas gradually replaced the former geocentric picture because their ideas did a better job of explaining what we observe about the universe. The key is to observe well, and then find the best explanation for what we observe. At some point (probably not initially) there should be an "Aha!" moment in which the new way of seeing things suddenly becomes "obvious," and self-evident.

This is a long-winded route by which to return to Barbour's notion of a static universe. One of the principal features we observe about the universe is motion. So the question becomes whether Barbour's concept of blue mists shining at instants containing time capsules will ever achieve an "Aha! moment in which we suddenly recognize that this is a better way of thinking about the observed phenomenon of motion. In all honesty, it is difficult for me to envision such an outcome. In this case, I think that if theory contradicts observation we need to re-think theory, very carefully.

In my own scheme, we are allowed to retain the idea motion while still dispensing with time, at least as being something separate from configurations of the universe. Perhaps not surprisingly, I find this a much more palatable way to proceed. As a way of looking at things, however, it represents nothing other than a beginning, a baby step. Nevertheless, I am encouraged by the fact that it leads directly and logically to the falsifiable "prediction" of the equivalence of mass and energy, as explained in my reference 4.

With apologies for being so verbose, good luck with your reading. It sounds as though we both will be immersed in it for a while. I plan to follow 'The Life of the Cosmos' with 'The Trouble With Physics,' and then move on to re-readings of Brian Greene, David Deutsch, etc.

Let's do figure out a way to stay in communication.

Cheers!

At the risk of violating forum "etiquette" by submitting back-to-back posts (this ideally should be a dialogue or a multi-logue rather than a monologue) I would like to mention one other interesting (to me at any rate) ramification to the definition of a particular time which I have proposed in my essay (a particular time is identically equivalent to, and is completely defined by, and only by, a particular configuration of the universe).

This definition provides a clear and direct link between entropy and the so-called "arrow of time." According to the above definition, any observable change whatsoever in the configuration of the universe would constitute a change from one particular time to another. If the configuration of the universe were changing randomly, however, as it would in a state of maximum entropy, then time, too, would change randomly rather than "advancing" in the manner to which we have become accustomed to thinking of it.

A god-like observer of a universe having a configuration which was changing purely randomly (as it would at maximum entropy) would not perceive that the universe was "aging" in any meaningful sense of the term. Changing, yes; aging, no.

In order for time to change in a manner which an observer would interpret as "advancing" in some meaningful sense, the configuration of the universe must change in a manner which is (or which at least gives the appearance of being) non-random. For the universe to be truly and accurately characterized by non-random motion, however, it must be in a state of less than maximum entropy.

The universe in which we live is (fortunately for us!) at a state of less than maximum entropy, and its configuration is changing (evolving) in a more or less predictable manner according to some rule or rules which we strive to understand. It is this predictability of the universe's evolution which allows us to perceive what we have termed "the advance of time" or "the flow if time." Hence the correlation between increasing entropy and the arrow of time.

Mr. Valletta,

In a nutshell, as Mr. Johnstone has said, there simply is no longer any "ago" to which we can go back. All the messy "grandfather" paradoxes (or T-Rex with missing tooth enamel paradoxes) are obviated; history cannot be changed. The notion of the flow of time as evolving configurations of the universe "explains" the psychological arrow of time which is so eloquently captured in the well-known lines from The Rubaiyat of Omar Khayyam,

"The Moving Finger writes; and, having writ,

Moves on: nor all your Piety nor Wit

Shall lure it back to cancel half a Line

Nor all your Tears wash out a Word of it."

Mr. Johnstone,

I'm astounded by how closely aligned our thinking is on this topic!

Even in a situation involving a statistical fluctuation in which entropy was randomly decreasing over some region, however, I don't think that an observer would perceive time to reverse. For example, if I were to look out on an interstate highway and see all the vehicles on the highway uniformly traveling backwards, I doubt that my first thought would be that time had somehow reversed; I'd more likely simply wonder why all the vehicles were backing up. If, on the other hand, I were to look up at the sky and see a 747 jetliner flying backward, I would be instantly and deeply confused (to say the least), because that sort of change in the configuration of the universe would violate the laws of aerodynamics (i.e., the laws of physics). Even in that bizarre case, however, I doubt that I would think time had reversed; more likely, I would question whether I was losing my sanity, or whether I were (hopefully) observing some bizarre optical illusion.

Our sensory systems and brains seemingly have been exquisitely programmed by evolutionary processes to observe our surroundings and to quickly and accurately calculate and predict the trajectories of the objects we see around us. This is how we have survived. Thus, while our brains may not fully understand all the abstract laws of physics, they understand well enough their practical consequences. I would strongly suspect that as long as our brains have the wherewithal to function, they will carry out this task to the best of their ability, regardless of how entropy may change. If we were to see the pieces of a broken cup leap up off the floor and reassemble themselves into a cup on top of a table we would question our senses, because that is not what we understand cups to do. Again, I suspect that we would be more likely to perceive it to be a violation of our understanding of the laws of physics than as a reversal of time. But these are mostly my off the cuff gut feelings rather than any carefully considered positions.

Regarding your comments about Barbour's action principle and best match procedures, I agree with you that it is not clear how these notions would fare in a universe at maximum entropy. Certainly food for further thought. Could this lead, for example, to some predictions or tests which would be falsifiable?

Thank you for your insightful observations!

Mr. Johnstone,

By all means, please do post your shopping list of guiding principles & relevant facts upon which to build a model! I'll look forward to it.

Back onto the topic of entropy and time, it must be obvious from my essay that I tend to take a very simple-minded, literal, naive view of the world. When thinking about entropy, I have a favorite "thought experiment environment" in which I imagine myself to be a microscopic being who resides on a molecule in a box of gas. The first order of business in this environment is to fasten one's seatbelt, because we're in for a bumpy ride, not unlike the bumper cars in an amusement park.

When the gas in my little "universe" is at thermal equilibrium, time (defined as configurations of my observable "universe") does change, but the changes are random (and hence "uninteresting"). On some very rare occasions, however, I might be fortunate enough to observe one of the rare, random statistical fluctuations predicted by Ludwig Boltzmann in which all the molecules simultaneously move to one side of the box. Wow! Now that would be exciting! I presumably would observe a temporary "compression" of my micro-universe, followed by a decompression and gradual return to equilibrium and random motion. During the compression and decompression phases, the observed motions of my neighboring molecules would, I believe, appear to be non-random, and hence "time" would briefly have a discernible direction (arrow), i.e., configurations would change in a seemingly non-random manner, but this short-lived "arrow of time" would gradually "peter out" and ultimately vanish after the gas had returned to equilibrium.

I fully agree with your comment regarding brain processes being too poorly understood to serve as *underpinnings* for a model of reality. (Ironically, however, it is these same brain processes upon which we must rely to judge the validity of a model once it has been constructed!)

The questions you raise about how all this stacks up against Mr. Barbour's Platonia are good ones, and I would like to hear how he would respond to them.

Cheers!

Mr. Johnstone,

The static picture which Barbour tries to convey has been, and remains, a huge stumbling block for me, and, in my view, it is unnecessary. The more I try to try to understand it, the more I fail to do so. Try as I may to make sense of it, the idea always ends up striking me as solipsistic. Since you are re-reading 'The End of Time' anyway, be sure to note Barbour's dialogue with Fay Dowker, which is introduced at the bottom of page 353.

As previously noted, my view continues to be that we can dispense with time as being something real *in and of itself* while not dispensing with motion. In fact, my view is that it is exactly motion which allows us to dispense with the old notion of time as some mysterious, stand-alone feature of reality while still allowing us to preserve our traditional psychological perception of "the flow of time." We simply need to shift mental gears to recognize that the flow of time is nothing more than the physical evolution of the universe, a process which necessarily involves motion and which should be described in a Machian, relativistic manner. This is not unlike the mental shifting of gears needed to move from thinking in terms of a geocentric universe to thinking in terms of a heliocentric universe. Nothing changes except the way we think about it, which, ironically, then changes everything!

Changing direction somewhat, I wanted to mention what I believe is another interesting aspect of thinking about particular times in terms of particular configurations of the universe. Although I have consciously tended, I hope more or less adroitly, to "finesse" the topic in my essays, we might reasonably ask how narrowly and/or precisely we may specify or define individual, particular times. It strikes me that the precision with which we can ever hope to define particular times is limited by two factors, one of which is our fundamental inability ever to have complete knowledge about the configuration of the universe, and the other of which is that even in a narrowly confined portion of the universe we will always be limited by the uncertainty principle from precisely defining a particular configuration/time. Hence, even at best, time at the quantum level will necessarily be "granular." At least food for thought.

Cheers!

Amrit,

Thank you for your comments and for sharing your essay, in which you wrote, "Ernst Mach said: "It is utterly beyond our power to measure the changes of things by time. Quite the contrary, time is an abstraction, at which we arrive by means of the changes of things". Mach is right. Time and clocks are man-made inventions."

I hope it is clear from my essay that I fully concur with this view. There appears to be a growing recognition that this is the case. What remains to be done is to explore thoroughly the practical consequences of this way of thinking. What predictions will it lead to, for example? I spelled out one "prediction" it leads to in reference 4 to my current essay. Unfortunately, Einstein beat me to that prediction by about 100 years, give or take. But I'm sure there are additional, totally new predictions that we can make if we set our minds to it. These are exciting prospects.

Cheers!

Mr. Johnstone,

A further comment regarding Julian Barbour's proposed model of a static universe. I try to remain open-minded toward Barbour's concept, difficult though it is for me to comprehend (this difficulty obviously could as readily reflect a shortcoming of my cognitive processes as any shortcoming of the concept itself). That having been said, however, I couldn't help being amused by a perhaps apropos comment which Einstein allegedly made regarding work done by Herman Weyl while they were trying to develop a unified field theory: "Apart from the [lack of] agreement with reality it is in any case a superb intellectual performance." (Quoted on page 45 of Lee Smolin's 'The Trouble With Physics.') Einstein's brilliance clearly extended well beyond physics to include the world of diplomacy. But that comment also captures my instinctive feeling toward notions of a static universe. Of course, instincts are not always to be trusted either. The proof is in the pudding, as the saying goes. What predictions could we make as a result of believing in a static universe that we can't make otherwise?

Mr. Johnstone,

That previous post was from me . . . sorry I failed to add my name at the top!

jcns

Mr. Johnstone,

On the topic of soliciting comments on our ideas from Julian Barbour, I have what I believe will be some encouraging words. When I submitted my essay to FQXi there was a provision in the submission form whereby I was offered the opportunity to name three persons whom I specifically would like to have as reviewers of my essay. (I hope I'm not "speaking out of school" here, as it were, but I do not recall seeing any stipulation that this information should be kept confidential.) So at any rate, the three reviewers I requested were Julian Barbour, Lee Smolin, and George Ellis (I'd noted Ellis's essay in last year's competition, too). Of course, I have no way of knowing whether this will actually happen, but if it does, I suspect the reviewers may well look at whatever posts are appended to the essay. So there is at least some hope that any comments which appear here will come to the reviewers' attention. As the saying goes, time will tell.

Btw, there recently has been a revised procedure whereby authors of essays are requested to log in before composing posts. The "system" supposedly will then automatically add the author's name at the top. This did not happen with one of my earlier posts (authorship was listed as "anonymous"). Perhaps there are still some bugs to be worked out. We shall see what happens this time. Even if it says anonymous, it's me.

I look forward to seeing your list of guiding principles and relevant facts.

Cheers!

jcns

Mr. Johnstone,

By way of addendum to my previous post, I'd like to add that inasmuch as Barbour, Smolin, and Ellis are all members of the FQXi community, and inasmuch as they are all known to have an interest in the broad topic of this essay, it does not take a rocket surgeon to conjecture that they might read the essay. By specifically requesting them as reviewers I was simply trying to improve the odds.

I keep coming back to comments such as the one by Brian Greene which I quoted in footnote 1 in my essay. Smolin has made what I see as a parallel comment: "We have to find a way to unfreeze time -- to represent time without turning it into space. I have no idea how to do this. I can't conceive of a mathematics that doesn't represent a world as if it were frozen in eternity. It's terribly hard to represent time, and that's why there's a good chance that this representation is the missing piece." (page 257, 'The Trouble With Physics')

Perhaps I'm missing some blindingly huge and fundamental point, but it strikes me that viewing "the flow of time" as being nothing more or less than the evolution of the physical universe (a totally accurate view, in my opinion) should be a good starting point for a representation of time which unfreezes it. Yes, of course, as always, the devil will be in the details. Some sort of Machian, relativistic representation will be required, and I unfortunately do not know how to formulate that representation. I'm hoping that some smarter people will know how and that they will take on the job of doing so. I can't help thinking that it might lead to real progress toward sorting out some of the long standing puzzles in physics. That certainly is my hope.

jcns

Mr. Johnstone,

Just a very quick reply to let you know I've seen your post, and agree fully with the points in your list. I'm departing very shortly on unplanned travel, so may be less able to focus on this topic than usual for a while. Good question about possible insights from Goldfarb's way of looking at things. I currently don't understand it well enough to have a worthwhile opinion.

My quick gut feeling is that it would help at this point to hear from some of the recognized professional "heavyweights" in the field regarding their views on the points we've raised. I suspect that our ideas will only "gain traction," as the saying goes, if they are taken seriously and "championed" by recognized authorities in the field. I fear that I've about reached the limit of how far I can take them without input and support from the professionals in the field. More later.

jcns

Mr. Johnstone,

This is being posted while I'm off traveling. I've been intending to mention one possible avenue we could explore which might prove helpful. In doing so, however, I'm obliged to admit that I've been seriously remiss in not having thoroughly pursued it already. In your post of 17 August you wrote, "Now, back in 'motion land', we agree that all quantities of time should be re-interpreted in terms of spacial displacements. You have clearly stated this in your essay, including the resulting derivation of the mass/energy equivalence obtained in this way. These are precisely the sorts of predictions & proofs we need to start building a model."

The mass/energy equivalence simply "popped out" on my very first experiment with substituting units of displacement for units of time, which I just happened to try with the definition of energy. This was, of course, most encouraging! What I am more than a little embarrassed to admit, however, is that I have not subsequently gone through systematically to apply the same procedure to the many other equations which appear in physics, i.e., doing the same substitution to see what other interesting things might pop out. Possibly other, similar "predictions" might pop out? Possibly even some that Einstein or others have not already made a hundred years ago? That would be exciting.

If you have any interest in pursuing this avenue, please by all means be my guest. And I trust it goes without saying that if you come across any interesting discoveries I'd be delighted to hear about them. Btw, this analytical technique was taught to me by my high school physics instructor, Mr. Carlyle Davidson, a wonderful teacher; he called it "dimensional analysis." Of course, he was not suggesting we replace units of time with units of displacement, but rather suggesting only that we carefully examine and compare units on both sides of our equations to be sure they match. If the units don't match, it's a clue that we'd done something wrong! If you do decide to give this a try, good luck and happy hunting!

Cheers,

jcns

Mr. Johnstone,

With sincere apologies for perpetrating this running monologue, I've had some recent thoughts relevant to our topic which I'd like to throw out for your consideration. As background, I'm currently re-reading Smolin's 'Three Roads to Quantum Gravity.' I assume you've probably already read it, but if not, I highly recommend it. I find that in re-reading these books I'm bringing new ideas *to* them, and as a consequence I'm taking new ideas *away* from them. What follows is an example.

In discussing the topic of zero point motion Smolin writes, "According to quantum theory, no particle can sit exactly still for this would violate Heisenberg's uncertainty principle. A particle that remains at rest has a precise position, for it never moves. But for the same reason it has also a precise momentum, namely zero. This also violates the uncertainty principle . . . . " (p. 83, TRTQG)

Now, in a Machian universe (as opposed to a Newtonian universe) we must ask the question, "remain exactly still relative to what?" There is no fixed reference with which to measure "stillness." The stillness, or lack thereof, of a particle in a Machian universe can only be measured relative to all the other particles in the universe. In order for a particle to remain absolutely still in a Machian universe, it would need to remain absolutely still relative to every other particle in the universe. But this could only happen if every other particle in the universe was also absolutely still relative to every other particle in the universe. In other words, it could only happen in a totally frozen universe in which no particle moved relative to any other particle. If this were to be the case, then, clearly, according to our proposed definition of particular times as being equivalent to particular configurations of the universe, time would not change in this frozen universe. All processes would stop, including the cognition of any sentient beings who happened to be so unfortunate as to reside in this dismal universe.

This strikes me as being a more fundamental way to explain why it is not possible for a particle to remain absolutely still than trying to explain it in terms of the uncertainty principle. Which leads me to wonder whether this same rationale might somehow also offer a basis for understanding the uncertainty principle itself? Or is this a variety of the chicken and egg question? I've not come up with an answer to this one yet, but would certainly welcome any thoughts on any or all of the above.

I hope all is well with you. I have just returned from my unplanned travel, and am about to embark on some previously planned travel. Will do my best to stay tuned in while traveling.

Cheers,

jcns