Time is an abstract concept that we experience. what we measure with clocks may not be the same as what we experience. There are many kinds of Time. Newton was the first physicist who used the symbol "t" for time in his equations to describe the physical phenomenon. This Newtonian Time was Absolute and was shown by Einstein that it is not measurable with our clocks. Our clocks measure Einsteinian Time. This time depends on the Frame of Reference as shown in the Special Theory on Relativity. The time measured by Galileo depended on Gravity and it is not the same as the Absolute Newtonian Time, since the pendulum moves at different speed depending on it's position. It moves slower on top of mount Everest than at the bottom. With General Theory on Relativity Einstein introduced another kind of time. This time is slower at the base of mount Everest than at the top. Neurologically there is the temporal lobe time. this is based on the way the temporal lobe arranges our experiences to form a narrative. there are disorders where this narrative is not exact and gives rise to phenomenon called de ja vu and jamais vu and amnesias. Genetically, there is another time which is based on the length of the telomeres on the chromosomes. they relate to the biological age of a cell or body which has limited correlation to the chronological age. this is seen in people whose physical health is much younger or much older than their chronological age. An example is progeria where the physical age of the person is highly accelerated. Therefore we cannot talk about a single entity called Time as it does not physically exist. thanks.

In general relativity it is possible to define mathematically space, time, matter, and energy by means of a metric tensor, so that these quantities are different faces of a larger concept that we are unable to comprehend.

From General Relativity we have to think of time together with space, matter and energy. For example, mass changes the speed with which humans "travel" through time. We can throw things or humans through time (as we throw things or humans through three-dimensional space), and the speed of passage of time is driven by gravity. The question arises: Is it the time that passes for humans or is it humans that go through time? I think that the answer is that it is humans who travel through time, and can even choose the rhythm of it.

The great merit of General Relativity Theory was to show that these four concepts, apparently distinct and without some correlation, are actually faces of a larger concept that we are unable to comprehend. Notice that by increasing the speed of a body by supplying it with energy, we are increasing its amount of movement, in other words its inertial mass, so that the space-time around it will be affected, deforming. Let us observe that there is no space without time, or matter without space, etc.

On the other hand, for quantum (microscopic) systems the energy is not conserved (uncertainty principle), ie: (delta E) X (delta t) < h. Therefore, the energy of a particle can spontaneously oscillate (without any mechanism). The question arises: Is it possible to measure quantum time? First, there is no quantum clock to measure microscopic events, such as tunneling time, because the clock would be microscopic and subject to the uncertainty principle, or uncertainty over time. The time becomes unpredictable in quantum clocks, and may even go back. Therefore, it is not possible to measure quantum time.

Quantum time probably can not be defined and may not even exist. There are several arguments in this regard. The importance of concepts such as time, location, and causality decrease or disappear.

Time is empty of meaning. Le temps est vide de sens.

instead of moments you'd rather speak of events. Au lieu de moments, vous devriez plutôt parler d'événements.

I like to speak of time in terms of eaten pies. J'aime parler du temps en termes de tartes mangées.

But this involves much more difficult problem of what is a number. Mais cela implique un problème beaucoup plus difficile de savoir ce qu'est un nombre.

Merci Igor Goliney . Et si pour les tartes le temps se définissait comme l'écart entre deux états successifs de la tarte dans l'espace ? ça pourrait resoudre le probleme des nombres.

La je considere le temps de la tarte, puisque ce temps est relatif à la tarte en sa qualité de matiere.

Thank you Paulo Laerte Natti

Time is empty of meaning. Le temps est vide de sens.

Je voudrais discuter un peu plus sur la phrase ci-dessus.

Je pense que l'espace, le temps, la matière et l'énergie sont différentes parties d'un concept plus large que nous ne pouvons pas comprendre, comme des parties d'un éléphant. Nous pouvons voir les parties, mais nous ne voyons pas le tout.

Je suis d'accord que quantiquement le concept de temps, ainsi que les concepts d'espace, d'énergie, ... deviennent diffus (on ne peut pas voir l'éléphant). Par contre, je crois que ce que nous appelons le temps (la patte de l'éléphant) n'est pas totalement dénué de sens.

J'aime l'idée qu'à un moment donné, après le Big Bang, il y a eu une transition de phase qui a généré de telles manifestations (espace, temps, énergie et masse), similaire à la transition supraconductrice (électrons - paires Cooper).

The notion of time is a successful illusion. La notion de temps est une illusion réussie.

Successful for us, hunter-gatherers. Réussie pour nous, chasseurs-cueilleurs.

We know that there are events that happened in the past. On sait qu'il y a eu des événements qui c'etait produits dans le passé.

We predict, extrapolate into the future. Nous prédisons, extrapolons dans le futur.

We developed a measure of time. Nous avons développé une mesure du temps.

Usually by some recurring process. Habituellement par un processus récurrent.

But not always. Sometimes we use decay instead of oscillation. Mais pas toujours. Parfois, nous utilisons la désintégration au lieu de l'oscillation.

In theory we built a model of continuous time. That model is quite successful in ordinary life. In physics it is not sufficient sometimes. En théorie, nous avons construit un modèle de temps continu. Ce modèle a beaucoup de succès dans la vie ordinaire. En physique, cela ne suffit pas parfois.

C'est l'une des raisons pour lesquelles j'ai voulu trouver une définition qui puisse servir à la physique et aux autres disciplines. Le ''temps'' traditionnel que nous utilisons à mon sens est un temps ''chasseurs-cueilleurs'' comme vous le dites Igor Goliney . Mais ce temps ne peut pas servir à la science.

Mais, pour donner un sens au temps, et là je rejoins Paulo Laerte Natti , c'est intéressant de se concentrer sur l’évolution de la matière dans l'espace. Et là, le temps naît et prend un sens du simple fait que la matière ou tout autre élément change d'état.

On a donc un concept de temps qui n'est pas absolu. Un temps relatif à la matière, peut-être l’énergie ou la pensée. On peut donc avoir plusieurs temps. Ce qui explique aussi que le temps peut avoir un début (avec le big-bang) et une fin.

This is one of the reasons I wanted to find a definition that could be used for physics and other disciplines. The traditional '' time '' we use in my opinion is a hunter-gatherer time, as you said Igor Goliney . But this time can not be usefull for science.

But, to give meaningful sense to time, and here I join Paulo Laerte Natti point of view, it is interesting to focus on the evolution of matter in space. And there, time is born and takes a sense of the simple fact that matter or any other element changes state.

So we have a concept of time that is not absolute. A time that is relative to matter, perhaps energy or thought. We can therefore have several times. Which also explains that, time can have a beginning (with the big-bang) and an end.

There was this long discussion about time 2 years ago:

https://www.researchgate.net/post/Can_time_be_factored_out_of_Newtonian_laws

When a pie is eaten, it is eaten. This is an invariant event. The number of eaten pies does not depend on the observer, This is a measure of proper time.

This does not work in quantum mechanics. Quantum mechanics calculates probabilities of the number of eaten pies between the start and the end. It uses the variable denoted t, but is interested in t -> \infty.

Time and space are percepted as whole by person. We live in and feel chronoto, we remember chronotops in connection with one or other event

From a physical point of view time is a parameter that enters in the fundamental laws of physics. This parameter has no meaning by itself, i.e., separated from the laws of physics. Of course, this implies a certain circularity which is unavoidable. For instance, we believe in the law of inertia : a free particle moves uniformly in straight line. But how do we know it moves with constant velocity? because it is not interacting with any other body. And how do we know it is not interacting with any other body? because it moves uniformly(this example is from Einstein and he knew what he was talking about). Another Guy who knew what he was talking about is J. Wheeler and he said(In his book Gravitation with Misner and Thorne ): Time is defined so that motion looks simple. I think this more or less explains what time is for a physicist(at least two(or four as you please) eminent of them).

Time is an abstract concept that we experience. what we measure with clocks may not be the same as what we experience. There are many kinds of Time. Newton was the first physicist who used the symbol "t" for time in his equations to describe the physical phenomenon. This Newtonian Time was Absolute and was shown by Einstein that it is not measurable with our clocks. Our clocks measure Einsteinian Time. This time depends on the Frame of Reference as shown in the Special Theory on Relativity. The time measured by Galileo depended on Gravity and it is not the same as the Absolute Newtonian Time, since the pendulum moves at different speed depending on it's position. It moves slower on top of mount Everest than at the bottom. With General Theory on Relativity Einstein introduced another kind of time. This time is slower at the base of mount Everest than at the top. Neurologically there is the temporal lobe time. this is based on the way the temporal lobe arranges our experiences to form a narrative. there are disorders where this narrative is not exact and gives rise to phenomenon called de ja vu and jamais vu and amnesias. Genetically, there is another time which is based on the length of the telomeres on the chromosomes. they relate to the biological age of a cell or body which has limited correlation to the chronological age. this is seen in people whose physical health is much younger or much older than their chronological age. An example is progeria where the physical age of the person is highly accelerated. Therefore we cannot talk about a single entity called Time as it does not physically exist. thanks.

the time is the length traveled by a photon in the empty space divided by the velocity of this photon.

Zareski, that's probably the best definion of the physical meaning of time. Though it is somewhat circular in the sense that you must first define "distance", it is in agreement with one of fundamental laws of physcis, i.e., the light principle.

As per definition of Arkady Raikin " Time is the distance between two paychecks"

The concept of time arises from our inability to include entropy in physical phenomena.

the distance needed can be measured