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We all experience that time moves, and most people just assume that it is the truth.

However, I see no solid ground behind it, since our perception would not change if it does. Our perception of moving time, as far as I know, just comes from our memory, long term and short term, and our sense of movement. Moving time does not seem logical either, since it would need some time to move in, which also would have to move in another time, etc.

Neither does it work with the theory of relativity, which views space and time as practically interchangeable. Therefore I wonder whether there are any good arguments for the existence of a movement of time.

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    Consider this alternative case: time does not "move". Only the present exists, you don't know any of the possible futures, you don't know but one of the possible pasts. You just have a memory of one past, ordered by your mind. Try thinking of now, completely forgetting the past et voilà: time does not exist, only change.
    – RodolfoAP
    May 1, 2022 at 23:50
  • @Masimatutu Unfortunately it is not correct to judge „the theory of relativity, which views time as practically identical to space.“ May I recommend to inform yourself about the different scientific views on time, space and spacetime on the basis of an introductive book on physics or by an article in wikipedia? – You can also find in the internet some information on our subjective experience of time.
    – Jo Wehler
    May 2, 2022 at 5:49
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    Most working physics models assume time realism and time move. Even for Kantian intuitionism time is a priori form of internal moving state... May 2, 2022 at 5:56
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    @DoubleKnot - I'd associate "time moves" with the A-theory of time where there is an objective present moment (presentism or eternalism with a 'moving spotlight'), most working physics models assume the relativity of simultaneity and thus seem more compatible with the B-theory of time, i.e. eternalism with no moving spotlight, the block universe.
    – Hypnosifl
    May 3, 2022 at 1:20
  • @RodolfoAP And even change does not exist, for the same reason, since change implies more than one "point in time". Only now can be said to exist, and even that's iffy, depending on what you mean by "exist".
    – jrw32982
    May 3, 2022 at 18:53

4 Answers 4

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Answer

Literally, time cannot move, because time determines motion of matter by way of v=x/t. However, it helps to think metaphorically about time, that we are an object and time comes towards us. This use of motion is figurative. It's important to keep the literal and the metaphorical distinct. Otherwise you are committing a category mistake.

Literally, motion is what we call the change in relative position over a passage of time. And yet, we talk about time moving, so that seems to appeal to our intuition. In fact, the Ancient Greeks used the metaphor that time overtook you from behind. We use the metaphor that it comes at us and we can see it coming. But in both ideas you are using figurative metaphor (time is like a river that washes over us) and in the abbreviated sense (time flies!), conceptual metaphor.

What happens we confuse the literal and figurative domain of discourse when discussing time? Poetry, art, and confusion. That's why analytical philosophers tend to be very explicit when dealing with abstractions and sometimes criticize Continental philosophers of complicating ideas by using language more figturatively. Philosophers of both tribes often explicitly recognize their use of figurative language in an example or even that they are using an extended metaphor to build a worldview. It's important to remember that uttering a sentence 'time moves quickly' doesn't physically dictate how the universe operates. To confuse the construction of language for the properties of spacetime causes headaches and misunderstandings.

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Newton described time as 'moving':

Absolute, true and mathematical time, from its own nature, passes equably without relation to anything external and thus without reference to any change or way of measuring time.

This should be contrasted with his conception of space which does not 'move'

Absolute, true and mathematical space is immoveable

In the synthesis of space and time by Einstein it is the latter conception that holds: that is spacetime is absolute, true and mathematical.

Of course this is very different from our very basic observations of time, that the present exists, that the past is past amd the future is open.

Aristotle himself held that time was the measure of motion, a view that is held by the British physicist Julian Barbour as outlined in his book, The End of Time. And so, time, in a sense does not exist. Aristotle, however, went further and said that motion itself was the actualisation of potentia. This is also the late philosophy of QM held by Heisenberg. This means, unlike in General Relativity, the future is open. And it seems to be the conclusion that Smolin draws in his book, Time Reborn. It is probably these two very different conceptions of time in GR & QM that is preventing the grand synthesis of the two in the still open question of quantum gravity.

An interesting idealist slant was put forward by the philosopher, Bergson in a debate with Einstein. He defined time through his notion of duration:

"Duration is essentially a continuation of what no longer exists into what does exist. This is real time, perceived and lived. Duration therefore implies consciousness and we place consciousness at the heart of things for the very reason that we credit them with a time that endures."

Although Einstein won that particular debate, I would say that Heisenbergs conception of time and motion, by way of Aristotle and QM, is likely to be the future of the subject.

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  • Actualisation of potential, is a very good point, which can encompass the multiple time lines of Many Worlds, & can fit with say Loop Quantum Gravity.
    – CriglCragl
    May 3, 2022 at 15:57
  • @CriglCragl: That's just nonsense. The Many Worlds theory drops the collapse postulate so nothing of the above actually relates to that at all. Before name dropping the names of theories perhaps some actual competence or research in those theories might be advisable? May 3, 2022 at 16:39
  • Heh, lol. All the worldlines can be interpreted as the potential within the unbranched worldline. Potential in the sense of quantum divergences, that can interfere, viewed from one worldline, not all worldlines.
    – CriglCragl
    May 3, 2022 at 18:05
  • @CriglCragl: LOL1. That's just your own personal interpretation that you've just made up. When it's published in a reputable journal let me know. LOL2, Have you ever published in a reputable journal? May 3, 2022 at 21:30
  • It allows grappling with time that is non-linear, eg branching, or emergent (from spin networks). That should be obvious..
    – CriglCragl
    May 3, 2022 at 22:48
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I read a nice bit of research I can't currently locate, about how split humans are about whether we move through time, or time moves over us. I think it tuned in on how people interpreted 'move this date forward', whether that meant speed up or delay. I would say this points to how moving in time or time moving, are fundamentally metaphors, & in physics we should seek more precise statements.

You are exactly wrong to say movement through time doesn't fit with Relativity. Minkowski's interpretation makes a direct analogy between the symmetry operations of moving in spatial dimensions, and time pictured as a dimension for symmetry operations. The spacetime manifold in GR can be pictured as already existing ahead of us like the past does behind, but our subjective experience is moving through spacetime with a substantial degree of continuity, which is to say symmetry between past & future in a specific sense. Or, as a presentist, you could say the algorithm linking past & future moves through the present.

What we have to reconcile with spacetime, is the thermodynamic arrow of time: the accrual of irreversible changes. GR is completely reversible, so you might expect no fundamental difference in character between past & future. QFT is very close to reversible, with the exception of deep inelastic scattering in Weak Field interactions, which fit with a higher CPT symmetry - it's widely thought the matter-antimatter assymetry derives from this. But, Weak interactions have very little impact on our experiences, mainly just beta decays. So that leaves a bigger question about time in our experiences. Which more deeply, requires a quantum-gravity theory, uniting GR's spacetime & the thermodynamic arrow of time which seems to emerge from quantum behaviour.

Rovelli's Loop Quantum Gravity is an example of attempting this, where a deeper reality of a quantum spin network selects between 'crowds' of possibilities while maintaining symmetries like The Principle Of Least Action over all. There's also Chirobelli's Purification Principle, picturing time as the spreading out of correlations, & attempting to find the simplest set of axioms GR & QFT can both be derived from. Deutsch & Marletto's Universal Constructor theory expands the classical logic of Turing Machines, to include objects as defined by sets of symmetry operations, & so constantly including counterfactuals about how they are arranged.

We have to account for what we see, which overall is a lot of persistence through time, with exceptions that we can understand through conservation laws. Those can be linked to continuous symmetries through Noether's theorem. QFT is our best theory, but it provides no account of where time comes from, it simply assumes it as background, & so far has only been able to integrate Special Relativity, ie flat spacetime. Relativity gives us a limit on the speed of propagation of information, and we can think of change as occuring in a 'channel' between isolated systems & speed of light, a ripple of information ground out by the laws of physics, in which sense there is no unified now, and there are no subjectivities to be moved past or who move through, there is only the ticking of light-clocks until only photons are left & time itself becomes meaningless (in Penrose's Conformal Cyclic Cosmology, which seems pretty compelling to me in accounting for the entropy assymetry at the Big Bang).

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  • Does this really answer the heart of OP’s question? I take OP’s “movement of time” to be akin to presentism or the “moving spotlight of the present”, where time flows at the ontological level. Presentism does not work with general relativity. And Einstein said the moving spotlight of the present may be outside science. The stuff about the second law is not relevant to this. The second law still exists in the block universe. And doesn’t emerge from known quantum effects.
    – J Kusin
    May 2, 2022 at 15:56
  • @JKusin: I see time 'flow' or movement as a misleading analogy for the emergence of quantum mixed states from pure states eg known quantum effects, information spreading out. There are plenty of defences of presentism in relation to Relativity eg jstor.org/stable/188696 & I've always seen deriving the existence of the present from block spacetime as the bigger challenge, it's of no interest to me that Einstein was a defeatist about that any more than his insistence 'God does not play dice'. Relativity is reversible, so it cannot account for irreversible events.
    – CriglCragl
    May 2, 2022 at 17:11
  • Is that the same link that gets shared around here a bunch which even says there are no models for general relativity and presentism? You keep saying just relativity. And yes irreversibility is not due to GR, the point is direction of time is not the flow/movement. The block universe has a low entropy side/portion and high entropy side/portion right? Yet no time flow at the block level.
    – J Kusin
    May 2, 2022 at 17:30
  • @JKusin: If Relativity was death to Presentism, there would be no Presentism. plato.stanford.edu/entries/presentism/#RelaPhys Our experience requires the spacetime dimension, to be reconciled with the Arrow of Time. What ordered the 'slices' of block like that, for you? As far as I'm concerned, the distinction between Presentism & Eternalism is currently unfalsifiable, so putting on blinkers about one when all we are sure about Relativity is that it's incomplete, is jumping the gun.
    – CriglCragl
    May 2, 2022 at 22:40
  • Well the paper you linked says this only concerns SR and that the task of GR is for another day, as I suspected. And the SEP doesn’t mention GR either. But there is no privileged space-like hyper surface (I think the term is close enough ) in GR, and that is typically taken as necessary for presentism. There’s no privileged reference frame. It’s a different argument than relativity of simultaneity which has proposal to work with presentism by your links. I agree these are currently unfalsifiable and may be forever.
    – J Kusin
    May 2, 2022 at 23:37
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Logically Sound Option 1 - the common experience: A ball is a three-dimensional object that exists now. The above is a trace of its past path through time and one spatial dimension, which creates a two-dimensional projection of four-dimensional object. That four-dimensional object we can call a segment of the history of a ball. As it goes along in the present, the three-dimensional ball interacts with other three-dimensional objects, including us, which have four-dimensional histories of their own.

Logically Sound Option 2 - the block universe: A ball is a four-dimensional object, composed of the entire past and future of the ball-process. The above graph is a diagram of a segment of the ball projected onto two dimensions (height and time). The spherical object that exists right now is a snapshot of the ball. The past of the ball existed in the past, the present of the ball exists in the present, and the future of the ball will exist in the future. The four-dimensional object doesn't do anything, we just look at sequential snapshots of it in its relation to countless other four-dimensional objects, including ourselves. Any interactions and events are just parts of the four-dimensional ball.

A close examination of 1 and 2 will reveal that they don't actually say anything different about the nature of reality and they don't make any empirical claims. They're just different definitions for a ball. Neither are right or wrong; definitions don't have truth-value.


Some ways to get it wrong:

It is popular to extend 2 by making a claim like, "the past, present, and future of the ball all exist simultaneously," which can sound very dramatic, but is reducible to the statement {t : t<B} = {t : t=B} = {t : t>B}, which is a contradiction. Nor is there a clever way around it with relativistic physics. There exist many reference frames in which events distant from the ball that are separated in time in the ball's frame are simultaneous. But there exists no reference frame in all spacetime for which any event in the causal past of the ball is simultaneous with any event in the causal future of the ball. See wiki: light cone.

It's popular (at least historically) to extend 2 to insist on strict determinism: that is, in every moment, the entirety of history before that moment and the entirety of the future of that moment are in-principle knowable. Such a claim contradicts observations of the expanding universe (things that aren't in your past now can get into your past in the future), and experiments in quantum mechanics (empirical evidence proves that the statistical model of quantum mechanics comports with reality, while a model that assumes that the statistics present in QM merely represent the experimenter's imperfect knowledge does not comport with reality).

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  • "is actually hot garbage if you think about it for a second" is not an argument. The Block Universe model is widely popular among professional physicists, & you didn't reference it directly, or account for that.
    – CriglCragl
    May 2, 2022 at 15:31
  • @CriglCragl The block universe is the description in my second paragraph, which is why, in the first sentence of my second paragraph, I described it as the block universe.
    – g s
    May 2, 2022 at 16:39
  • Re: hot garbage, I will edit the relevant paragraph, although it's depressing to consider that there might be anything to be gained by doing so.
    – g s
    May 2, 2022 at 17:21
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    I don't care about your language, though the site has guidelines. Serious & intelligent people hold the block-universe stance, I think a majority of physicists when polled. It just reflects on you to dismiss that without consideration.
    – CriglCragl
    May 2, 2022 at 17:28

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