➡ A logical proof of the impossibility of a tangible universe consisting only of three spatial dimensions, hence the necessity of motion, and thus time ⌛ rather than the reverse 😎. Followed by a proof of the possibility of reversing time in specific but very common universes, and the realization that these perspectives provide greater psychological flexibility to intuitively accept the relativity of time.

Warning : The following text was first written for the above linked video, so even with a quick adaptation the overall impression is probably better when listening to the video, plus you'll get context specific humor!

This text is also a response to the all too common assertions, whether provocative, ironic, or naive: "Time does not exist!"

We live in a 4-dimensional spacetime world, with three purely geometric dimensions, for example x,y,z in an orthogonal coordinate system, and one temporal dimension usually abbreviated as "t", a dimension that is considered, unlike the other dimensions, to only be traversable in one direction. In practical terms, in our complex world, we cannot go back in time! That being said, it is necessary to ask three fundamental questions about time: (1) Why does it exist? (2) Are there real universes in which we can go back in time? (3) Why can't we reverse time in everyday life?

Point number one : Why does time exist ? It's first necessary to understand that time, although regarded as the 4th dimension of our real world, is not as intuitive as one might think. We have the impression that it flows, and that it possesses a flow rate that varies depending on our subjective perception, etc. But these perceptions are deceiving and do not help in grasping the true nature of time, with its imperative existence and necessity in our physical world. The mistake we generally make is to focus on time as an intuitive basic dimension. Unlike distances, which are palpable, time is a psychologically abstract dimension in the sense of being intangible, fleeting, requiring complex mechanisms for precise measurement. Adding to the confusion, it's the official 4th basic dimension of the spatiotemporal Universe in which we live. Therefore, we have the false impression that it cannot be replaced, for example, to more easily justify why it exists through a more intuitive entity.

In fact we can replace it with something more intuitive, more imperative, and tangible: motion!

Motion defines time very effectively because it encompasses it. Indeed, there are no possible motions without their displacements occurring within a certain interval of time, meaning lengths per unit of time.

Since motion is more tangible and intuitive than time, we can easily demonstrate the reason for the existence of motion in our Universe, and in doing so, also demonstrate the reason for the existence of time.

In other words, a world made up of material entities in three dimensions, x, y, z, can only exists, and even more so, be observed, if these entities can move. It's from considering these motions in the form of accelerations and velocities that the concept of time emerges, but not the other way around! This means that motions in all their forms are fundamental expression of our world, from which arises the essential existence of time. Although it is more practical to use basic units of length and time like meters and seconds to describe and measure these motions, rather than using units that directly represent motions, such as velocity (v) and acceleration (a), and then extracting time, which is not very practical as a concept reversal.

Time is also relatively abstract and fleeting, whereas material entities in motion are very concrete.

This, for simple reasons of practical understanding, further emphasizes the conceptual primacy of motion over time. Although in a purely mathematical context, one could argue the opposite because the "t" axis is very practical for performing calculations, but these are generally not, and often by definition, the most concrete elements of our world.

One can also be convinced of the primacy of motion over time in another way, for example:

Motion is absolutely necessary for the measurement of time. From a sundial and the mechanical clock to the atomic clock, we always measure time through motions (*1), vibrations, and transitions, which are forms of repetitive motions that, for greater precision, must be increasingly rapid and regular.

(*1) of course we can do rough estimation of time just with our mind, but “motions” are present there too as some form of neuronal activities, electricity flows along some neuronal axons if we count silently with a regular tempo or if we do a more analogical estimation based on feelings or body sensations.

A global universe in which time, and therefore motion, does not exist is impossible, since we exist and are capable of motion. In other words, for such a universe to exist, there would either have to be absolutely nothing in the infinite x, y, z directions, thus no motion and no way to measure time, or the entire Universe would have to be completely static. Yet again, since we are part of the global universe and observe that it moves, a completely static or entirely empty global universe is both absurd and impossible.

Point number two : Are there real micro-universes in which one can go back in time? Yes, if the concerned micro-universes are sufficiently simple. Let's assume a universe composed solely of three mechanical switches: A, B, and C, capable of being in only two different states, namely 0 and 1. Initially, in the first state of our experiment, the switches display 0, 0, 0, then move to display 0, 1, 0, then move again to display 0, 0, 0. Well, a micro-universe composed solely of these three switches returning to their initial positions also undergoes a reversal in time if all its conditions are exactly as they were during the first state. In the context of this micro-universe, there is no means to differentiate these states (no wear and tear, no way to count anything independently of the three switches, etc.). It's an entirely theoretical scenario, but it makes more sense if a video is played in reverse: all the pixels on the screen replay their different states in reverse, literally rewinding time in the micro-universe of the screen by reversing their states until presenting us with impossible situations in the real world, like a broken egg from a fall reconstructing itself to return to the hand of the person who broke it.

Point number three : Why can't we move through time in reverse in most real-world situations? Because our reality is too complex. However, if in a space bubble large enough at a given moment, we could reverse the motions and states of all molecules to put them back in the state and position they were in a few seconds earlier, we would already have a sort of very convincing local time reversal. For example, the reconstitution of an egg from its broken and flattened state in a pan.

Relativistic Note: It is easier to have an intuitive understanding, albeit very partial, of the relativity of time if time is first perceived as motion. This is because we are accustomed to seeing motions change in magnitude due to the action of forces on objects involved, rather than being directly perceived through clocks, which, by definition, have been designed to be as stable as possible to provide maximum accuracy to measure time.

First Conclusion: Time exists because motion exists, and motion exists because a material universe in 3 dimensions without any motion is as absurd as a completely empty universe, both of which are even more absurd considering they contain observers.

Additional Observations: Motion always implies covering a certain distance over a certain period of time. It should be noted that in a certain conventional spatiotemporal reference frame, with distances and times situated between the ends of the scales, i.e., between 0 and infinity (excluding the limits), and for simplicity, we take the practical reference distance of 1 meter, with a reference time of one second.

By comparing these two unit figures with each other and with the ends of each scale, we obtain a single realistic motion of one meter in one second, five cases of immobility (no motion), two cases of impossible infinite speed, and one case of indeterminate speed due to an infinite distance covered in an infinite time.

Denying time is also denying motion, and good luck with that!

Second conclusion: One can simulate a return in time provided that the object in question is very simple. It is sufficient to reassemble the object as it was in its primordial state, and thanks to its digital nature, the computing world, particularly considering screens in a video context, allows the retrieval of initial screen states, passing through all intermediate stages, thus performing the equivalent of a time travel in the micro-universe constituted by the screen pixels. This enables us to visualize actions that are impossible in the real world.

Psychological Generalization Regarding Time:
Why do we so often find phrases like "Time does not exist" with 1,560,000 results mentioned on Google as of September the 16 of 2023? This is absurd given that motions exists, and multiple answers are possible as why it’s like that, and here we have a few of them:

Time is an abstraction relative to (derived from) motions, meanings that it's an attempt to break down motions into two parameters. The first, very concrete parameter is the distance traveled, and the second is time, which is an abstraction derived from motions and is measured by standardizing motions, for example, by making mechanical chronometers. So, we measure the non-spatial parameter of a previously unknown motion by comparing it with the non-spatial parameter of another known, standardized motion. The numbers we obtain, for example, are seconds, which are abstract units. We cannot touch, see, or sense them independently of an object or particles in motion (*1 written complement in the description section). As a result, time is more difficult to grasp than distances like meters, and when general relativity informs us that time is relative, we doubt even more. However, relative does not mean non-existent; actually quite the opposite, like existing and complex at the same time.

Time defined in our Western societies often oppresses us, especially in stressful contexts where many obligations are present: we must be on time, wake up in time, and so on, this leads to a quite understandable frustration, especially when the pragmatic concept of time is well understood, we never seem to have enough of it!

Time is often frustrating because we cannot objectively reverse it, stop it, or slow it down in our daily lives! And of course, when we think about trying to influence time, it's usually to gain some advantages, like the possibility of making up for lost time! But here's some good news: even though we can't change the overall flow of time, we can change the relationship we have with it. For example, by trying to speed up our actions and perceptions, we subjectively find ourselves in a world where time seems to pass more slowly, which is generally pleasant.

The illusion of an eternal present without memory of the past or vision of the future, an eternal present that wouldn't need time because it's always there, present and timeless! Yes, it's always there and doesn't need memory or anticipation to exist, yes! And yet, it moves! 🌎🌍🌏😎 And it changes everything!


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