Time, Relativity, and the Mayfly Self

The Physics of Time

 

Even before Einstein, physics was never really supportive of our common-sense ideas about time. Humankind has long believed that the past and the future are very different, the one over, done with, fixed, the other ahead, open, malleable. The past keeps gaining new territory from the future across the boundary of the present. The calendar date of tomorrow becomes that of today, then of yesterday. All this seems to force upon us the conclusion that now is something that moves. 

Science, with physics at its base, has been a great success in explaining the phenomena of our world: thunder, billiards, fire, elevators, airplanes, the ability of fish to swim and viruses to infect. What did Newtonian physics have to tell us about this moving now? Nothing. The equations of physics contain variables for time, t₁, t₂, even t₀, but no “now.” 

With Einstein, physics stopped being unhelpful regarding our shared sense that the now moves, and became hostile, or at least unfriendly.

According to special relativity, for those in one speeding railroad car event A precedes event B, while for the passengers in the oncoming train on the other track B precedes A.  (Trains were Einstein’s vehicles for his thought experiments, but at train speeds, especially US train speeds, A and B would have to be very, very close in time from the perspective of both trains to get the temporal order disparity. We can make that shift quantitatively more dramatic by substituting, for the trains, spaceships heading towards each other at a respectable percentage of the speed of light. If they are far apart, all the better.)

Another way to put the key point is that one train’s now traveled through event A before it got to B and the now of the other train was at B before moving on to A. Which train’s now is the real one? You already know the answer: each is correct in its own framework and neither framework, neither now, is privileged. So says special relativity.

There are frameworks at a great distance from us and moving away in which Caesar’s Crossing the Rubicon is now (that is, in its simultaneity hyperplane), and distant frameworks moving towards us in which New Year’s 3000 is now.

Relativity has no unique now sweeping across the events of history. If there is any moving now at all, then there must be a vast number of them, and we jump from one to another when ever we start or stop moving, speed up or slow down, turn or spin. They cannot be called upon to divide an objective universal past from an objective universal future. 

So, no now is privileged in the grand sense, and it seems to follow that every event in the entire history of the universe, from the Big Bang onward forever, has as much claim to be now as every other event. It may make this a little less counterintuitive to reflect that whenever you have thought “this is now,” you have been right. So perhaps it is intrinsic to every event, wherever located in space and time, that it is now.

Einstein:

Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence. [Relativity (1920), Appendix 5, 120.]

“Past, present, and future are all equally real. They all exist.” (Brian Greene, Video “The Fabric of the Cosmos: The Illusion of Time” 26:55). “The past is not gone, and the future isn’t non-existent. Past, future, and the present are all existing in exactly the same way." Max Tegmark, MIT, Ibid.  27:20. Emphasis added). This idea that each point of space time is, objectively, as real, with as good a claim to being now, as every other point is often called by the philosophers of time “block eternalism.”

It is widely believed to follow from block eternalism that the moving now is an illusion. Einstein: “For us who believe in physics, the separation between past, present and future has only the significance of an illusion, albeit a tenacious one." [Letter to the family of M.A. Besso, 1955. There are several translations of this floating around. Here is the original:  “Für uns gläubige Physiker hat die Scheidung zwischen Vergangenheit, Gegenwart und Zukunft nur die Bedeutung einer, wenn auch hartnäckigen, Illusion ]

Note that Einstein is not saying that for a given event there is no difference between its future and its past. Those are quite separate portions of 4 space. Direction in time isn’t relative. His point is that there is no objective line that divides the past from the future. 

Greene goes into a little more detail on the illusory nature of the moving now:

It is as though our minds provide the projector light . . ., so that the moments of time come to life when they are illuminated by the power of consciousness. . . Within each individual slice, your thoughts and memories are sufficiently rich to yield a sense that time has continuously flowed to that moment. This feeling, this sensation that time is flowing doesn’t require previous moments – previous frames to be “sequentially illuminated”.” (The Fabric of the Cosmos, 139-40.)

At first I read this to say that an internal projector in our minds itself moved along illuminating on moment after another. So, although there is no objective moving now, now really did move – subjectively and illusorily. This would raise such embarrassing questions as whether different people could have their internal projectors shining on different days – so that for you the now was on Monday while my now had already reached Thursday. If this is impossible, what is it that would keep each of our subjective projectors together? A master projector synchronizer would seem a lot like an objective moving now. Then again, perhaps it would make no difference if your subjective now was on a different day from mine. Why couldn’t I now be talking to someone for whom that conversation took place three days ago? These perplexities led me to think I might have misinterpreted Greene.

What I believe Greene is really saying is only that whenever we happen to think about it, we “project on” memory data that convinces us that the now is moving. This happens every time we activate the projector. We always summon the same illusion of passing time. No “apprehending” time passing is any worse grounded than any other; but none is any better.  

That no event in space-time has any better credentials than any other to claim existence or now-ness and that the moving now is an illusion is the view of many of the physicists whose professional specialization brings them in contact with the question and of probably a plurality of the philosophers of time.

So let me assume that the eternal-block-no-moving-now-every-moment-really-exists theory is right and ask what that means for the common sense view that it is now as you read this paragraph, that yesterday is no longer now and that tomorrow isn’t yet. How can it be that your celebrations of last New Year’s Eve exist in every bit as real a way and have the same claim to nowness as your reading of this sentence?

The puzzle is if last New Year’s events and events of your reading this blog really have exactly the same existence and now status, how it is that you are (or seem to be) reading this only and not also celebrating New Year’s?  If no time is privileged, why is it that this time seems so definitely to be yours now – to be privileged for you?.

 

The Mayfly Theory of Self Identity

To try to unravel this, it is going to be helpful to survey a little of the theory of personal identity as it turns up in common sense and in the philosophical literature. If you already are familiar with personal identity and related matters, you might want to skip the next 6 paragraphs. 

In ordinary life we have various reasons for wanting to distinguish the same person over time. It is important that the person the surgeon has on the operating table is the same person as was diagnosed with appendicitis. It is unjust if the person sent to prison is not the same as the person who took the money. In the latter case, however, we would make an exception if the hands grabbing the money out of the safe belonged to a body with electrodes in its brain through which a remote operator controlled those hands. Then it would be this remote operator who committed the larceny.

Novelists, and sometimes even we in the non-fiction world, opine that someone was not really himself, or not the same person, after her trauma or after four years at college or four years in prison.

Extreme cases of amnesia and of multiple personality call for nuanced judgments about personal identity properly to describe personal relationships (whom did he love?) and fairly to distribute praise and blame for actions. Philosophical thought experiments about brain transplants, divided brains, duplicated brains, and memory transfers can put our intuitions about personal identity into conflict, a conflict that is sometimes, but not always, resolved by being more precise as to the purpose for which we are asking “Is this the same person?”

Among the purposes for which we might want to know whether Person B is identical to Person A is whether A ought rationally fear pains or welcome pleasures that will befall B in the future. For an easy example, if A is the donor in a brain transplant and B is the donee, it is rational pre-transplant for A but not B to fear the root canal on B’s molar scheduled for after the operation. Philosophers argue whether the person entering a Star Trek transporter will feel the pains of the person who steps out on the alien planet (or whether it would simply be lights out for the person on the dematerialization pad).

Then there are philosophers who contend that 10-year-old-A should not fear the pains of 80-year-old-A, either because of difference in the physical constituents of the brain, or because of the difference in memory contents, or because of difference in values, purposes, and projects, or because of some combination of the above.  The self of the 10-year-old might, 70 years later, feel none or only a portion of the pains of the 80-year-old, being, by then, at most a minority shareholder. 

Yet a little more philosophy may help me set up the intuition I want to encourage before we face our problem head on. Bertrand Russell: "There is no logical impossibility in the hypothesis that the world sprang into being five minutes ago, exactly as it then was, with a population that 'remembered a wholly unreal past." (The Analysis of Mind, 159). It would, of course, require enormous intelligence, calculational capacity, and engineering resources to accomplish this feat. It is an extraordinarily implausible hypothesis, but that was not Russell’s concern. His point was simply that neither our memories nor any other evidence could strictly disconfirm the creation-plus-5-minutes hypothesis. I need only that we could have memories that are fake in the less dramatic sense that it was someone else who had the experiences that laid in those memories. As long as the memory content was right, there would be no way for us to tell.

              

Finally, I will get to the point. To be brief, and brutal, you exist only in this moment. It was not you who celebrated New Year’s Eve last. That is, it was not you in the important sense of someone for whom, with perfect physical and metaphysical knowledge, it would have been rational to be apprehensive that she would herself suffer any pains that you now feel. Properly informed, that self of New Year’s would have known that it would not survive to peruse this blog. 

Your whole existence, all that you have or will experience, I am sad to say, may not extend beyond the reading of this post. Your memory, of course, is strongly to the contrary. It gives you confidence that it was you who collected those New Year’s experiences. Our theory has it, however, that your memory deceives you completely on this point. It was a predecessor self who formed those memories in the brain that you inherited. 

So, the solution to the puzzle that preceded this section, and I think the only solution, is that your self is reading this post and a different self, a predecessor of yours, is doing the celebrating, and neither self has any better claims than the other to existence or nowness. This is the way to make your confidence that the now is here and not at any New Year’s Eve, compatible with the theory that there is no objective moving now. 

Of course, for medical, or legal, or social, or pretty much any of the reasons for which we usually ask the question “Is that the same person,” you are indeed the same person as the New Year’s celebrator. It is only in knowing the true state of affairs that it would be self-interestedly irrational for the party-goer to fear having any experience that will be yours today. It is only the real metaphysical you that is limited to the here and now, and for most ordinary purposes this metaphysically correct measure of personal identity is irrelevant. (For some nuance on this, see Appendix.)

The theory I am outlining is, I think, implicit in suggestive remarks by such eternal block proponents as Einstein and Greene, whether or not they fully faced its implications. I call it the “mayfly theory”  to emphasize the tight temporal limits it places on personal identity. Your existence registers on only a short segment of the time dimension of space-time. 

Here, unfortunately, our language of tenses and durations is less than adequate to its task. Each of our physical-metaphysical selves occupies a small region of space-time, but we occupy our region “forever.” It never goes out of existence. So, in one way your existence is short – on the time dimension of space time; in another way your existence is eternal – because your segment of space time exists always.

This is perhaps why Einstein, in his letter to the family of his recently deceased friend, took the physics of time to be consolatory, preceding his statement about the lack of separation among past, present and future with this: “Now he has also taken leave of this peculiar world a little before me. That is of no significance.” To what extent we really ought to be consoled will get a little attention in the Appendix.

The Duration Problem 

As I have outlined the mayfly theory, a person exists in a physically and metaphysically basic way only for a “moment” – a weasel word if ever there was one. I then, without any justification, went on as if a moment might stretch across the reading of a blog post. Why so long? 

If the basic idea is right, isn’t the you who started reading the post as different from you now as is your New Year’s self?  If you didn’t say, “this is really now” when you first started reading, you could have. So, on the theory we are working with, the blog-beginning-you cannot be the same as you. 

This reasoning can be repeated, driving the duration of your metaphysical existence shorter and shorter.  Can it be stopped before we get down to the Planck second? (Generally thought to be the “quantum” of time or shortest meaningful time or shortest well-behaved time – 10^-43 seconds.) Surely, that is too short for a significant human existence. Some consolation it would be! Maybe the intersection of brain functioning and metaphysics puts the mayfly moment at the duration of the perceived or “specious” present, something near the duration of a clock second. That is a lot longer than a Planck second, but still makes for a pretty meager biography. 

Perhaps there is a principled argument for stretching the duration of the mayfly moment, but I haven’t found one. I am equally at a loss for a way, without making use of mayfly personal identity, to make consistent our experience of time with the eternal-block-illusory-moving-now theory. That leaves three options: First, abandon the theory of time we have been assuming (and risk a fight with the physicists); Second, leave the duration problems as footnote objection to the block-mayfly theory, hopefully to be successfully dealt with later; Third, bite the bullet by arguing that the memories created by a chain of selves, however many and brief, could create the illusion of a single self across time as well as the illusion of a moving now. This latter seems the intellectually soundest option, although, on it, any consolatory virtue of the theory has, I think, gone negative. 

For a different take on the moving now, sometimes called the “spotlight theory,” which takes it to be non-illusory, although consistent with an eternal block see http://lawrencecrocker.blogspot.com/2017/07/two-or-more-moving-spotlights-of-time.html?m=0. That post is not, admittedly, orthodox now-spotlight theory, as it takes up the possibility of two different nows moving across the 4 dimensional block, and asks whether the spotlight could sweep backwards.

It appears that is possible to draw support for a view like that of Einstein and Greene from traditional theology. See “Is the Moving Now an Illusion if God is Omniscient?” http://lawrencecrocker.blogspot.com/2014/06/is-moving-now-illusion-if-god-is.html.

Appendix of Some Further Issues

Ambiguities of “Eternity” and the Question of Consolation 

As mentioned in passing above, our old-fashioned vocabulary of time words is ill equipped to express the eternal-block-no-moving-now theory of time. In particular, a human lifetime, is not eternal old-talk (eternal-O) (not of infinite duration). On the theory, however, every human experience exists as fully as any other event in space-time. Your experience now is eternal new-talk (eternal-N).  How much is eternal-N like eternal-O? Is it enough alike to use the same word, or do we thereby court only confusion?

If your life, or a potion thereof, were eternal-N, would that be something to celebrate?  For these purposes, let us put the mayfly theory aside and assume that your personal identity stretches all the way from birth to death.  Now you are told that your tenth birthday party exists just as really as does your reading this sentence and that both will exist for eternity-N.

One possible response: 

Y:   Well fine, but, as I do not seem to be experiencing that birthday party, its eternal-N existence doesn’t do anything for me.

I:   Perhaps you are not experiencing it only because you are under the spell of the illusion of a moving now.

Y  But that illusion, if it is an illusion, is always-O with me. It must somehow curtain me off from whatever advantages eternity-N has to offer. I don’t suppose I am going to be suddenly freed from the illusions of a moving now when I die, thereafter enjoying the benefits of eternity-N.  That sounds like cheap fantasy fiction.

   Or am I supposed, postmortem, to experience my whole total life altogether and forever? What in the world would that be like?

I:  Well, there is, of course, a time dimension within your eternal-N spatio-temporal region. As the old saw has it, time is a way to keep everything from happening at once.

Y: Then do I rerun my life event by event forever (a la Nietzsche’s eternal recurrence) so that inside eternity-N there is still the illusion of a moving now?

I:  Well, maybe.

Having handled with such aplomb your concerns about the claims of eternal existence of block-eternalism having temporarily put aside the mayfly theory of personal identity, let me return to the idea that the existence of the metaphysical self is, in fact, very short. I contend we know what it is to have an eternal-N experience if this extreme mayfly theory is right. It is exactly what you are experiencing at this moment. 

Y:  How can you call that any kind of eternity -O or -N?

I:   Well, it’s happening isn’t it? And do you have any good reason to think it hasn’t always and will always be happening? If it were really only a passing instant, what are the chances, against the universe’s billions of years, that this instant, your instant, should be the special one?

Y: That is an obviously fallacious use of probability. What, after all, are the chances of being on just this planet out of a reference class of all the real estate of the universe? And even if it were improbable that this instant is now, that is just the fact. I know it hasn’t always been, because, just half an hour ago, I was . . .

I: Ah, but on the mayfly theory that half hour ago is a matter of prior-O events of which your knowledge comes from memories passed to you by your predecessor selves. That a moving now has gotten to this event and is departing is an illusion. What is not an illusion is that you exist at this event and that it is now and will exist and be now forever-N.

I think that these are the responses that I should make to your criticism of the mayfly version of the eternal-block-no-moving-now theory, but I am not at all sure that they should satisfy you. More fundamentally, it is not clear to me, with or without mayfly personal identity, that eternal-N really has anything important in common with what we have always before thought of as eternal.

The Implications of Special Relativity 

Yet more pressing is whether Einstein’s relativity of simultaneity, the headwaters for all forms of the eternal-block-illusory-moving-now theory, really implies that theory in its mayfly form or any other. 

Belief in Unbelievable Metaphysics 

Even if the arguments were to convince you that it must be so, it may be hard to believe that, e.g., a predecessor self exists and celebrates New Year’s exactly as you exist and read this. 

Going back at least as far as Parmenides and the fifth century BCE, there have been metaphysical theories that have been sincerely contested for but in which no one, including their authors could possibly have wholeheartedly believed. In the particular case of Parmenides, he and his pupil Zeno argued, with force and sophistication, that the only thing that really exists in a uniform, uncreated, unchanging, space-filling, sphere. 

I am sure that Parmenides really believed this. I am also sure that he didn’t. For the latter proposition I would cite, as modest evidence, the second half of his sole surviving writing. It apparently set out an account of the common sense world in some detail, unfortunately mostly lost. Parmenides regarded this as a description of unreality, of “mere appearance. Still, he did deal with it in a depth that suggests he was covering his bets in case he might be wrong about that sphere. He believed, I think, at the same time inconsistent things.

We all know people who would sincerely say that they are convinced of some proposition but act sometimes, or even all or almost all the time, as if they believed the opposite. The idea that people cannot believe, really believe, contradictory things is empirically bad psychology, a psychology we have inherited from religious soul theories as rationalized by Descartes. Psychological evidence is overwhelming that the human mind and human consciousness are not nearly as unitary or transparent as thought to be by Cartesians (those who know they are Cartesians and those who have no clue).

It might be that  Parmenides, Plato, Leibniz, Hume, Kant were great philosophers in part because they were so single minded as to be unmoved by the bizarreness of their own philosophies when measured against what they themselves had believed before having been captured by their own arguments. (At least Hume, however, recognized that the power of habit prevented even him from achieving a practical commitment to his own theories. He took himself to have proved conclusively that it is irrational to think it more probable than not that the sun will rise tomorrow. He admitted, however, that such irrational beliefs as that in tomorrow’s sunrise did control his out-of-the-study life.)

Anti-intellectuals, a recently resurgent demographic, and intellectuals who think of themselves as “realists” in the non-philosophical sense of that word, take it to be a sufficient refutation of a theory that it is “unbelievable.” The mayfly theory of the self surely qualifies.

There are at least two things to be said in favor of unbelievable theories, however. The first is, as we all know, that some unbelievable things have turned out to be true, from heliocentrism to evolution to non-Euclidean space and, important for current purposes, to the relativity of simultaneity. The arrogance of equating unbelievable with false is one of the best documented of obstacles to intellectual progress.

The second positive of unbelievable theories is that even when false they may be fecund. Elaborating them, arguing for and against, developing variations, and alternatives may lead somewhere important. It doesn’t always. Many unbelievable theories are just dead ends. When, however, there are apparently strong arguments in favor of an unbelievable theory, it is very often worth taking seriously. 

Life Consequences of the Mayfly Theory 

For this Appendix item, I would like, again, to put aside the arguments that the mayfly time period might be utra-short and suppose that a self lasts for a respectable period of time, although still well shorter than a normal lifetime.

Would believing this affect one’s life? If many people believed, would it have social consequences? First, I think we have to tune these questions down a couple of octaves. As discussed immediately above, no one is going to believe a mayfly theory, at least, no one is going to believe it at all wholeheartedly. It is going to be a belief of a distinctly intellectual, theoretical sort. This is not to say that it isn’t genuinely held, however, and even intellectual-theoretical-academic beliefs can have consequences beyond the learned discipline and out into ordinary day to day life.

It is not inconceivable that one might derive some consolation in the face of death from the mayfly theory or a variant. It is also conceivable that one might respond by trying to pack more of what makes life valuable into the present, not sacrificing so much for future experiences that only one’s successors will enjoy.

An extravagant extrapolation: if a lot of people became very convinced of the theory, then there could be too little postponement of pleasures, too much postponement of hard work, and, as the economists would put it, too little savings. That would not be good for the species, which might explain why our hardwiring is so uncongenial to mayfly sorts of personal identity theories.

The effects of a belief in the theory, inevitably only partial, will be further moderated by the fact that even to the extent that you disbelieve that you, yourself, will benefit from your savings, you have a concern for your successor selves that you do not have for random strangers. It is rational to want to ameliorate the sufferings of the successor selves of your body – of your person in the way we identify your person for almost all purposes. You will not feel their pains, but they are closely connected to you. They will have many of your memories, your values, your projects. Most of their friends and loved ones will be the successors of your friends and loved ones.

For the relation of the thesis that there is no privileged now to the traditional theology that God knows everything about the future, see:https://lawrencecrocker.blogspot.com/2014/06/is-moving-now-illusion-if-god-is.html.

For imagined evidence that the moving now is real, but there might be more than one of them, one perhaps moving "backwards," see https://lawrencecrocker.blogspot.com/2017/07/two-or-more-moving-spotlights-of-time.html