As of October 13, , a second is the duration of about 9 billion periods of the electromagnetic wave emitted by a Cesium atom, when it changes from one level of energy to another. Astronomic clocks were the first to be used by man. Before clepsydra and hourglasses egg timers , we counted the days, taking advantage of the colossal clock that is the sun. There have been methodological difficulties in calculating the mean solar day, because one has to assume that the sun moves at a constant speed, or to calculate the mean sidereal day, because one has to assume that stars keep the same relative position with respect to each other.
In precision clocks, the regularity of movement comes from a pendulum that oscillates under the influence of gravity: the duration of a half-cycle depends on two elements, the length of the pendulum and the intensity of gravity which is not uniform at different earth locations.
The unit of time is thus defined using a measure of length. There are ties between time and movement, but time is not movement: movement varies, and is polymorphous, while time does not change. But time, which is a number, does not exist without the soul nowadays we would say the mind , outside of the soul.
It is a boundary conceived to delimitate, not a part of time. The measure, of time determines what separates the beginning and the end of a movement. Plotinus , a neo-platonician philosopher, raised the issue of self-reference in a definition of time based on time, and said that this was a confusion between what is numbered measured and what numbers measures. In contrast to Aristotle, he argued that time existed before number was applied to it.
One should remember that, at the time of Plotinus, Christianity strongly influenced philosophy and science: Adam had committed a sin, and since then the soul of man was separated from God and thrown out of eternity into temporality. Saint Augustine says that there is no time outside of the soul.
Here is the quotation that follows the epigraph:. But, then, how is it that there are the two times, past and future, when even the past is now no longer and the future is now not yet? But if the present were always present, and did not pass into past time, it obviously would not be time but eternity. If, then, time present—if it be time—comes into existence only because it passes into time past, how can we say that even this is, since the cause of its being is that it will cease to be? Thus, can we not truly say that, time is only as it tends toward nonbeing?
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As another illustration, Plato wrote that time is a moving image of eternity. If time only exists by and for the soul, then what does one measure when speaking of time? The opposition between the phenomenological description of time using memory by Saint Augustine and the mechanistic explanation of Aristotle of time being the number of movement has never fully been solved in Western philosophy.
The materialist tradition also favors eternity in relation to time: atoms and the emptiness of the universe are infinite, uncreated, and imperishable. Galileo , the founder of modern physics, considered the universe to be written in the language of mathematics—an idealistic idea opposite to Aristotle's empirism—and saw the world as expressing an eternal order of things, that we can conceive, although we cannot feel them. Galileo's idea of an eternal and undifferentiated time replaced the concept of a time consecutive to movement.
From Galileo to Einstein, separating rest from uniform movement became a matter of frame of reference, or, put differently, a matter of position of the observer. A popular example of the role of the observer's position is when we are seated in an immobile train, and the departure of another train gives us the impression that our train is moving.
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Galileo also invented thought experiments: if one makes the hypothesis that a theory is true and one demonstrates that reasoning based on this hypothesis leads to dead ends, then the theory is false. Performing such a thought experiment, he concluded that the speed of fall of an object is proportional to the duration of the fall and independent of the mass of the object.
This was the first historical occurrence of a physical law being expressed using the parameter of time. Thus, with respect to his own definition, using the name of duration is inadequate. Time according to Newton is a mathematical variable having one dimension, continuous. Only two topological objects have this characteristic, a line and a circle. It thus follows that time is either infinite or cyclic. Conversely, wrote Kant , one can neglect all information coming from our senses sensitive data , but never can one leave out time and space, which are indispensable for any representation.
The representation of space cannot, therefore, be empirically obtained from the relations of outer appearance. On the contrary, this outer experience is itself possible at all only through that representation. In it alone is actuality of appearances possible at all. Appearances may, one and all, vanish; but, time as the universal condition of their possibility cannot itself be removed.
Physicists chose the linear version of time on the basis of the principle of causality, which was first introduced by Leibniz. There are several descriptions of this principle, 21 ie, the relationships between causes and effects. First, a cause necessarily precedes its effects this precludes a cyclical time. Second, the same causes induce the same effects and the repetition of a cause leads to the repetition of the effects, sometimes leading to cycles. I emphasize that cyclical time is not synonymous with repetition of cycles. Third, there is a mandatory chronology between the effect and the cause, and the effect of a cause cannot act retrospectively on the cause.
In cyclical time, a cause A leads to an effect B, and in the future of B one could come back to the past of A: while growing older, one could enter one's parents' past and prevent them from meeting one another! Cyclical time is not time, since there are then no distinctions between past and future. And fourth, the past cannot be modified it will always be that what occurred in the past did occur.
As of the 19th century, the definition of what is a cause became more complex as the science of thermodynamics developed: mathematical distribution functions were used to describe gas molecules in terms of probabilities, a rather new concept. More recently, at the beginning of the 20th century, a form of causality principle without cause arose from quantum physics: with certain types of phenomena, which are causally related, a chronology is mandatory, but one cannot establish that the first phenomenon causes the second.
Despite these new ideas about the nature of causes, physicists kept the principle of causality as a valid axiom for their work. In conclusion, in the terms of physics, the principle of causality makes it such that time cannot be cyclical repeating itself indefinitely , but that cycles in time can exist phenomena can repeat themselves. The other time, Tempus, is time as we experience it subjectively. It does not flow uniformly, it depends on our emotional status, in the broad sense of activation, vigilance, and mood: time is elastic , and the phenomenology of this characteristic has been the theme of many studies.
Tempus, the subjective or psychological time can not be measured with Chronos, but nevertheless can be compared with it. Tempus rarely flows as we would wish it to: a minute, being bored or an hour of passion cannot be measured using the tools of physics. This is why we carry watches, so that we do not lose track of time.
Temps de crise et temps ordinaire. Un itinéraire de recherche à côté de l'institution
In myths, time is considered as what will occur, the future. Many myths speak of a world before time, a world in which time had yet to come into existence. Amusingly, astrophysicists have a similar argument when they describe the origin of the universe.
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Etienne Klein 24 reinterpreted a Greek myth about the birth of time as follows: At the beginning of all things, Gaia arose from Chaos and gave birth to her son Ouranos while she was sleeping—out of time. Gaia was in the center, Ouranos all around, and there was no space between them. Gaia became pregnant and the Titans, children of Ouranos, could not be born because of the lack of space. One of the Titans, Kronos, made it possible to chase away Ouranos, and this enabled space to be created. Gaia was able to give birth to the Titans. They later procreated, and this succession of births created time, Chronos.
According to Klein, a confusion we make between time and future dates back to that myth. A major contribution from this author is the notion that time has never been thought of as what produces duration. Biological clocks such as the suprachiasmatic nucleus deal with the generation of circadian rhythms. They are the temporal coordination of spatially distributed neuronal networks, as well as brain structures that relate to Tempus, ie, the prediction and evaluation of durations.
Many observations and experiments have confirmed that living species are able to measure durations. The measurement of short durations, of less than a second, are probably less dependent on attention or emotion, although these can modulate even the measurement of short durations. The evaluation of longer durations, from seconds to hours or weeks, involves cognitive functions such as attention, emotion, and memory. More than years ago, the Swiss psychiatrist Auguste Forel , known for his work in psychiatry, neurohistology and for his extensive studies on ants, noticed that bees came to his breakfast table regularly at the same time, even when no breakfast was being served.
Indeed, bees can be conditioned to go at a given moment of the day to a given location where food was previously provided. A theoretical model on how biological systems could measure duration, ie, how a brain system might generate a continuous metric, was proposed by Treisman in This has been criticized on the following basis: it could be that each biological function has an inbuilt duration measuring system, for example, a different one for motor action, for vision or for audition. Moreover, there might even be independent duration measuring systems for subfunctions in each motor or perceptive system.
David M. Eagleman summarized issues raised by the handling of time by the brain:. A challenge for the brain is that afferent signals from the different, sensory modalities are processed at different, speeds. When receiving signals from several modalities, how does the brain determine the timing correspondence? The answer seems to be that the brain dynamically recalibrates its expectations. The requirements of such coordination leave room for illusions to occur.
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For example, with short durations, when the event occurs in the immediate proximity or during an eye saccade, there is compression of time. An experiment by Stetson 31 illustrates this recalibration of duration, in the case of the visual modality. When a delay of ms is artificially introduced between the moment of pressing a button and the occurrence of a flash of light, the subject rapidly adapts to this delay, which seems progressively shorter.
When the presence of this delay is abruptly interrupted, the subject can have the impression that the flash occurred before he or she pressed the button. These adaptations of duration judgments are independent of one another, in the sense that if duration compression or dilation occurs in one perceptive aspect or system, eg, vision, it generally does not occur in other modalities, eg, audition.
These observations speak in favor of more than one neuronal networks that judges duration, since the temporal outputs of these networks can become desynchronized. When thinking and speaking about time, we confuse a series of terms. Imprecision, ambivalence, and contradiction are often how we speak of time, and this influences how we think about it.
A major imprecision is that we do not set apart time and temporal phenomena: without noticing it, we attribute to time properties that are those of the temporal phenomena that we observe. For example, succession of days and nights, or the repetitive obligation to fill out tax declarations, will lead us to say that time repeats itself, and thus that is is cyclical. Defining time is a challenge. Indeed, defining a concept is feasible when the concept is referred to something more fundamental. And nothing has been found that could be considered to be more fundamental than time.
Thus, definitions of time are circular; they are tautological, as found by Aristotle, who saw time as the amount of movement with respect to before and after. When thinking about time, we remain under the influence of old analogies and metaphors. We hesitate between two pillars of Greek philosophy, Parmenides and the concept of immobility, and Heracleitus and the concept of a future.
Heracleitus has shaped our discourse about time for the last two millennia, and still today, we cannot consider other metaphors than that of time analogous to a river and the flow of water.
Space remains, while time passes: could this be a manner to differentiate them? But if we define time as a machine that produces instants, then we have to conclude that it is not time that passes, but that all these instants are fabricated by time. We should learn not to confuse time with duration, time with future, or time with temporal phenomena. And I confess to thee, O Lord, that I am still ignorant as to what time is.
How, then, do I know this, when I do not know what time is? Or, is it possible that I do not know how I can express what I do know? Alas for me! I do not even know the extent of my own ignorance. Saint Augustine National Center for Biotechnology Information , U. Journal List Dialogues Clin Neurosci v. Dialogues Clin Neurosci.
Temps de crise et temps ordinaire. Un itinéraire de recherche à côté de l'institution - Persée
Author information Copyright and License information Disclaimer. Abstract We are unable, using our five senses, to feel time, nor, using our intelligence, to define it, because we stand inexorably within time. Keywords: time , duration , temporal phenomenon , philosophy , psychology , physics. Si personne ne me pose la question, je sais ; Si quelqu'un pose la question et que je veuille l'expliquer, je ne sais plus.
Introduction What, then, is time? If no one asks me, I know what it is. If I wish to explain it to him who asks me, I do not know. Saint Augustine 1 An initial issue regarding time is that, in our Western mode of thinking, we have retained Heracleitus' metaphor of time being a river which we never can enter twice, because it never remains the same. Philosophical distinctions are defined in Box 1. Box 1 Guide to philosophical concepts cited in this review Materialism: matter constructs reality; all things are composed of material and all phenomena including consciousness are the result of material interactions; opposed to any kind of transcendence superstition, mythology, supernatural, spiritualism, theology, religion, deism, idealism.
Temps de crise et temps ordinaire. In: Communications , 94, Through the account of a research trajectory, this text offers a personal reading of institutions and reality. The division of the latter in two opposite categories, ordinary and exceptional, rules our representation of the world, and also our practical, political and social organisations. Starting from the key-event of the genocide and Nazi concentration camps system, this interpretation can be applied to different topics such as collective risks prevention, natural or industrial disasters readiness, and victimization studies.
Dedans, dehors l''institution. Les dispositifs meurtriers. Le temps des horloges ne vaut pas, il fait le lit de l''insignifiance. Tout en nous refuse cet accouplement du mal radical et de la routine bureaucratique. Ainsi, l''arme du crime fut l''organisation, et non les instruments militaires. La notion de dispositif a une origine militaire, et en effet les petits soldats des dispositifs meurtriers n''ont pas besoin d''y voir plus clair que Fabrice del Dongo sur son champ de bataille.
Le champ des risques et des crises : l'ordinaire et la catastrophe. Mais ce sont aussi de bons lieux d''observation du politique en train de se faire. Point de vue des victimes et sciences sociales.