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I encountered a rather stupid question which I don't quite understand. - "Why can we remember the past but not the future?" It sounds cool when I first read about it but I think about it more, about how to explain it to a person who doesn't know physics, this questions starts to become rather dumb, because "remembering" implies something that happen in the past or has happened, so in order to remember the future, one has to have a predetermined future, so the only way that one can remember the future is that one has his future set. So what am I misunderstanding here. Does psychological arrow of time implies that? Instead of understanding why one can remember the past but not the future, I would like understand how will life be like, if we can only remember the future (which I find it to be absurd logically and semantically). Can someone give me a scenario of this?

How do physicists define time? I mean the normal sense of time only flows forward. The moment one talks about time flowing backwards, the person must be using a different definition.

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What's being referred to here is roughly the question that Einstein called the "problem of the now". That is, our experience suggests a tensed, flowing time, and the phrase is only "absurd" insofar that it seems to clash with our experience. The underlying problem is to answer why or how it is that we seem to perceive time as flowing, and the phrase is most commonly uttered by someone subscribing to a Aeternalist (also called Perdurist or Detenser) philosophical position on the nature of time. Such people include Einstein, Hilary Putnam and I would think a good proportion of physicists. I myself would consider myself subscribing to it but would not put myself in the same sentence as Einstein or Putnam.

The problem is that much of physics, especially after classical thermodynamics and special relativity, implies an objective, real "eternal" existence to the past and present as well as the now, since these things are different for different observers, and one can choose and freely become any such observer, in principle: these musings are roughly contained in the Rietdijk–Putnam argument. Moreover, physical laws at the microscopic scale seem to be reversible: the World's state at any given time is an invertible function of its state at any other time, or at least that's what many of us believe. This latter position is one of the indestructibility of information and is, for example, essentially Leonard Susskind's position in the debate of the Black Hole Information paradox. An objective reality of both past and future seems to be contained in the state of the World.

Nothing in physics seems to point to the "pre-eminence" of "now" as opposed to past and future. Or, for that matter, the pre-eminence of the past over the future - whence your question.

A good layperson's summary of these ideas is reviewed in:

Brian Greene, Randall MacLowry & Joseph McMaster, The Illusion of Time, Video documentary by WGBH-Boston (TV) of the PBS network.

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  • $\begingroup$ Non-integrability of all but a handful of potentials is perfectly enough to define timescales on which even simple systems "forget", hence there is both a past that we can't remember and a future that we can't predict. $\endgroup$ – CuriousOne Jun 25 '15 at 4:20
  • $\begingroup$ I think it is the the way physicists interpret time that makes it problematic. For example, many people ask the question why an egg will shatter but it won't reassembled and relate this to the idea that time only move forward. Why can't they look at this as egg shattered -> egg reassembled -> egg shattered, so time still move forward. Why must they look at this as an example of time moving backward? That is my concern. Am I right to say that physicist associate time with a state of an object? That's why when egg reassembled, it is moving backward in time. $\endgroup$ – user10024395 Jun 25 '15 at 5:30
  • $\begingroup$ @user2675516: Physicists associate time with the readings of suitable clocks, all of which are systems in a (periodic) non-equilibrium. Such systems can only move one way, otherwise we don't call them clocks and we don't use them to measure time. A broken egg does not make a good clock any more than a whole one. $\endgroup$ – CuriousOne Jun 25 '15 at 5:44
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If time was reversed we would remember only things we hadn't done yet and nothing that had happened. The laws of physics work equally well forwards or backwards, yet our everyday experiences of cause preceding effect, not the other way around makes this seem counter-intuitive.

Just imagine some kids playing cricket in a universe where time is reversed. In a panic they run (backwards!) to a yard where they will be playing. There is a shattering sound and shards of glass from a nearby window suddenly rise up off the ground and assemble themselves into a single pane. The force of this event hurls a cricket ball towards the batter, who is now worried that "predicting the past" the window might have just been broken because of the ball (he can no longer remember it). He swings the bat from over his shoulder and behind his ear to behind himself, catching the ball a glancing blow which just happens to send the ball towards the bowler. The possibility of a broken window is now forgotten and the kids keep playing, no longer panicking.

Because of cause and effect we only remember the past, not the future because time flows in only one direction.

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  • $\begingroup$ Actually, the laws of physics only work one way but there is a microscopic time reversal symmetry which one can (naively) interpret as if all processes should be reversibly. In reality no practical process is reversible and there are only a handful of idealized ones (for integrable classical potentials) for which that symmetry would actually have some physical meaning. $\endgroup$ – CuriousOne Jun 25 '15 at 4:18
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In this case one could argue that 'remembering the past' would be a methaphorical expression to describe being able to predict the future. Experimental evidence says that people that have declared being able to predict the future are either scammers, delusional, self-fulfilled prophecies or just extremely intuitive. As far as I can tell, there hasn't been conclusive scientific evidence of precognition.

Assuming that as a fact, then the absence of precognition (or deterministic precognition) is a observational fact. The mainstream scientific theory of time and cognition says that the brain is a system that creates memories upon facts that happen as consequence of thermodynamical time flow, and because of that future events are fundamentally indeterminate. There is no evidence against this theory, which is the reason is mainstream

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The future can be remembered if we acknowledge that at any given moment we are deciding by our thoughts and actions what future possibilities will occur next, amongst an infinitude of choices. Every possible reality in which you live exists on some parallel reality (frequency)

We remember the past easily because we just came through it, we bring that frequency into the present.

We remember the future by choosing a specific future first, then by way of resonance, being in tune with that future, the frequency of that future, we can then perceive that future as it reveals itself.

All happening from the point of view of the now moment. What do you think of that? =)

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The primacy of Reason has always grounded my cognition of Existence, which resulted in an Objectivist epistemological world-view, Existence exists, being exactly what it is, regardless of opinions to the contrary. If one is deaf, and blind, and is unable to perceive one is standing upon a railroad track, with a speeding locomotive swiftly approaching one's place upon it, one's lack of perception of Reality results in one's removal from it. The raid doesn't care if you are wet. The wind, if you are cold. Existence, if you cannot identify it.

In fact, the identification of Existence is the very basis of all consciousness and all knowledge, which must be kept in an exact contextual hierarchy to preserve its meaning. Therefore, Existence exists before any consciousness of Existence may ensue, any consciousness, itself, being part of, and determined by, Existence. Thus, Existence is completely Determined.

So, the concepts of "chance," "choice," "chaos," and "randomness," apply only to ignorance of the intellect, and the scope of these concepts shrink as the intellect expands its identification of Existence.

To claim the people, who built the Empire State Building, could have "chosen" NOT to do so...or...that ANY past event could have been in ANY WAY different from what it actually was...entails the notion Existence could be something it is not. Logic need not be Logical. Knowledge need not be possible. "A" need not be "A." An acorn could grow into an oak, or into an elephant. Fact is, what happens must happen exactly the way it does happen, as it cannot happen in any other way...no matter one's fantasies to the contrary.

Remembering the future does not happen in reverse, like the shattered egg rebuilding its shell. Future memory is experienced with the same flow of time one normally experiences in normal Reality...forward. It is as if one's intellect has malfunctioned from its normal mode, like a skipping record needle, or a glitch in a DVD, causing the "player" (intellect) to jump ahead on the "recording" (Existence) for a moment.

The event of having a future memory is not something which is controlled by the mind, but seems to be the result of an error in normal sensory experience...as if our intellect is riding the groove of normal time and is "bumped" out of it and into another for a short time. The experience is not a "feeling," but a very dramatic cognitive break in our flow of sensory experience...like watching a film suddenly skip ahead in the action...but, in this case what skips is your entire sensory experience. The experience of future memory is always very startling, unexpected, and virtually always terrifying...as the one experiencing it is taken by surprise and utterly lacks any understanding of what is happening.

This means future memory events generate powerful emotional reactions in those experiencing them. Those very emotional states seeming to be a trigger to the experience itself. Meaning, the experience of future memory may be dependent upon the future emotional pulse it causes. The future event shown by future memory, may be mundane and quite unremarkable, but the emotional reactions created during the experience...the time between the "now" and the arrival of the "foreseen" moment,as the mind tries to grapple with it,...and the traumatic arrival of the "remembered" event, which is then experienced in one's supposed flow of "real time," are profound. The greatest burst of emotion coming as the revealed event is experienced the SECOND TIME.

What is the nature of an Existence wherein one may perfectly experience a future, supposedly random, and unpredictable, event, intellectually...then witness the event take place, exactly as it was envisioned and experienced, even just 30 seconds before?

Existence is Determined, and seemingly, our intellects, although responsible to Existence, ride upon its Identity, part of it, spawned by it, enjoying the show of it, which allows our ignorance of it...to provide the growth necessary to avoid the torments of Eternity.

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  • $\begingroup$ This seems more philosophy than physics, and doesn't really fit as an answer on this site. $\endgroup$ – JMac Apr 10 '19 at 16:08

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