By |

mind-544404_1920.png

Ingfei Chen reports the impression of neuroscientist György Buzsáki that what the neurons in our brain measure is not a tempo that is constructed by clocks. Rather, such neurons measure change or acceleration that occurs to us outside cultural constructions of that change.

To most of us, it seems self-evident that our brains must have something like a “sense” of time—a system for tracking the passage of time, analogous to the visual system, which detects changes in the visible world. Yet our heads contain no temporal “sensors”—and “neurons in the brain have no access to human-constructed instruments, so they have no clue about time,” Buzsáki noted when we spoke last month. Whatever our neurons are measuring, it’s not the tick of an actual clock. Moreover, he argued, both time and clocks are cultural constructions—inventions that modern societies have inherited from their predecessors. Some indigenous tribes experience “time” very differently. The Amondawa people of the Amazon, Buzsáki said, think in terms of “change”—when tribe members cross life thresholds, such as menstruation or marriage, they are given different names—but have no words for months or years and don’t know how old they are.

Speaking with Buzsáki, I found myself wondering what my brain was actually sensing when I seem to feel time flowing, second by second, minute by minute. “It has to be measuring something else, such as change or speed or acceleration, for which we do have sensors,” Buzsáki told me. If that’s the case, then “time” isn’t an absolute thing that our brains can “track” or “measure”; it’s more like an organizational system for making sense of change in the world around us and coördinating our lives.

“Of course time is change,” Edvard Moser agreed. Another way to describe his lab’s analyses of the L.E.C. would be to say that it uncovered changing sequences of activity during episodes of experience. “We call it ‘episodic time’ to emphasize that this is not ‘clock time,’ ” he said. “I still do think we have to call it something. It doesn’t really help us a lot to call it ‘rates of change’ ” (Chen 2019).

Chen, Ingfei. 2018. ‘The Neurons that Tell Time.’ The New Yorker. December 3, 2018. https://www.newyorker.com/science/elements/the-neurons-that-tell-time.

By |

neuron-3567980_1920.jpg

William Meissner notes that when the diurnal rhythm of the nervous system is examined, experiments can be used which deprive us of external prompts regarding time. Such prompts are categorised into time-sources which are artificial (such as clocks), versus those which are natural (such as sunlight).

It should be noted that all biological systems evidence biological rhythms, most of which are patterned on a diurnal basis (Moore-Ede et al. 1982). The human organism is no exception to this principle (Wever 1979). Even in man there exist a variety of diurnal rhythms. The more obvious rhythmic systems include the cardiovascular system, the cardiorespiratory system, renal system, gastrointestinal system, endocrine systems, changes in blood constituents, patterns of activity in the autonomic nervous system, and variations in mood and performance. Also rhythmic patterns in the neuromotor system are significant for regulation of walking, running, etc. Rhythmic activity has also been identified in the nervous system as a whole. As Gooddy (1969) commented, “If we accept the notion of the nervous system as a clock form, we note immediately the complex nature of its structure. The final clock, by which perhaps we say ‘we know what time it is,’ or ‘we know about time and its passing,’ is the last abstraction from the innumerable subsidiary clock forms. Even at a level of single brain cells, rhythms have been demonstrated by Phillips (1956). And the common clinical tool of the electroencephalogram (EEG) provides us with objective evidence of summated and abstracted rhythmic nervous activity” (248-49). The inherent diurnal rhythmicity of the nervous system was established in a series of experiments depriving subjects of all environmental time cues-without the aid of any artificial time aids (e.g., wristwatches) or natural time-related phenomena (e.g., light-dark sequences), diurnal rhythms were found to persist throughout lengthy periods lasting as long as several months (Gifford 1981; van Cauter and Turek 1986).

Investigators found that these free-running rhythms did not coincide exactly with a twenty-four-hour cycle, but varied among individuals, approximating a circadian pattern but tending in humans to extend the cycle slightly beyond the twenty-four-hour measure. When exposed to environmental cues, however, these rhythms tend to resynchronize, more or less, with the normal twenty-four-hour cycle. This pattern of temporal organization undoubtedly has adaptive evolutionary advantages and serves the interests of internal organization and synchronization of functions, both physiologically and psychologically. We can conclude that such synchronizations are an aspect of normal and healthy functioning, and that pathological dysfunctions can reflect disruption in these systems. Experiments in sleep deprivation and common phenomena such as jet lag seem to reflect this understanding. The incidence of health complaints is higher among night-shift workers than day workers, presumably because of the desynchronization between normal restactivity cycles and environmental time cues (Moore-Ede et al. 1982) (Meissner 2007, 225-26).

Meissner, William. 2007. Time, Self, and Psychoanalysis. Lanham: Jason Aronson.

By |

atom-1472657_1920.png

Alex Pasternack describes how timekeeping is the measurement of the passage of a second, which equates to how long it takes for a certain amount of radiation to be given off by a cesium atom in the universe.

The primary aim of timekeeping is to measure the passage of a second. To be precise, that is equivalent to the amount of time it takes for the hyperfine radiation given off by a cesium-133 atom at its ground state as it transitions between energy levels, and its electrons oscillate exactly 9,192,631,770 times.

These days, counting a second depends upon firing a microwave beam at one of these cesium atoms and counting the effect on its electrons. At that scale, the slightest aberration can knock a clock off its count. And then there are the effects of gravity, which Einstein’s theory of special relativity showed can shift the pace of time.

“At the nanosecond level—a billionth of a second—every clock has its own personality,” Matsakis wrote in an email. Each clock will tick faster or slower at certain times, and generally, scientists can correct for this using software. The trickier part is understanding the rate–sometimes sudden, sometimes slow—at which a clock’s ticking may be changing. “We must be on the lookout for deviations from the predicted behavior, and be sure to predict well.”…

“Once I had this definition of time, that it’s a coordinate that you can measure the evolution of in a closed system,” Matsakis said. “Now, I think of time as something that, stripped down to its essence, is a measure of interactions,” an idea based on Einstein’s theory of relativity, which pins time and space to the relative motion of objects. “It’s an intriguing thought: if you don’t have interactions, time is irrelevant.”

He offers an example that begins at the end of time. “One way that time could stop is if the universe could reach a cold death. If our universe expands forever, and the suns die out, and they become black holes which evaporate over eons, what’s left is a rarefied gas, a cold gas that’s uniform across the universe. With everything the same, how can you have time? There’d be nothing to measure time. Time would stop, and not with a bang. It would just peter out.”

The relative interactions that govern the movement of time explain why events in the universe don’t easily fit along a timeline. “Imagine that people witness Al Capone robbing a bank in 1930,” he said. “Then, a supernova a thousand light-years away is observed somewhere on Earth in 1987. Did the star explode first, or was the bank robbery first? It depends on the observer.”

In an email later, I mentioned Nieztsche’s proposal of eternal return. Matsakis shot back: “It is very hard to define fundamental things. I haven’t tried to define ‘place.’ Socrates spent years trying to define justice. Maybe they were right about him corrupting the youth.”

It was Aristotle’s contemporaries who first mastered the calculation of the passage of time, or chronos, and it was they who also recognized another kind of time, kairos—the moments that define our pleasures and our pains and our deepest feelings and thoughts.In other words, the kind of time that can’t be metered by any clock.

Tensions linger between this sense of “time,” which Henri Bergson would later describe as “duration,” and the tick-tocks of “the time” overseen by the timekeepers. Now more than ever before, argues Douglas Rushkoff in Present Shock, distractions keep the latter version of time in a kind of tug of war with the former.

“We spent centuries thinking of hours and seconds as portions of the day,” Rushkoff told David Pescovitz last year, “But a digital second is less a part of a greater minute, and more an absolute duration, hanging there like the number flap on an old digital clock.” The rush of the present and its seemingly infinite, hyperlinked possibilities means “a diminishment of everything that isn’t happening right now—and the onslaught of everything that supposedly is.”

But according to time, not everything is happening at once, as Wheeler joked. Could the Master Clock, I wondered, with its steady, orderly pace, remind us that the world isn’t moving any faster?

But not even this ticking will be the same in the future. With new clocks, the way that time is counted will change. And in time, the definitions of time will change too, if not the questions that endlessly circle it.

“What I tell people is, I can’t tell you what time is,” Matsakis said, “but I can tell you what a second is” (Pasternack 2014).

Pasternack, Alex. 2014. “How the master clock sets the time for the world.” Motherboard, November 7, 2014. https://motherboard.vice.com/en_us/article/ 3dkd5b/demetrios-matsakis-and-the-master-clock

By |

january-2290045_1920.jpg

Peter Coveney and Roger Highfield contest the characterisation of the week as being linked to celestial movements. Instead they note that the week is contingent upon social norms and contexts, which are distinct from the rhythms and revolutions of the planets.

The week does not have a basis in the motions of the heavens. As Michael Yong, Director of the Institute of Community Studies in London, put it: ‘The Sun has not been the only master. Humans can create their own cycles without having to rely on the ready-made ones. No other creature has demonstrated so much independence from astronomy. No other creatures has the week.’ The week probably arose from the practical need for societies to have a time unit smaller than a month but longer than a day. Communities run more smoothly when there are regular opportunities for laundry, worship and holidays. Ancient Colombia used to have a three-day week. The ancient Greeks favoured ten-day weeks while some primitive tribes today prefer a week of only four days. The seven-day week derived from the Babylonians who in turn influenced the Jews (though the former ended it with an ‘evil day’ rather than a Sabbath, when taboos were enforced to appease the gods – perhaps the origin of the restrictions on Sunday activities). Its popularity has defeated a number of attempts at change. The French tried to decimalise it after the Revolution but their ten-day week was scrapped by Napoleon. In 1929 the Soviets attempted to introduce a few-day week and in 1932 extended it to six, but by 1940 the seven-day week had returned. Just as the week ignores astronomy, so does the modern technology of timekeeping (Coveney and Highfield 1990, 43).

Coveney, Peter, and Highfield, Roger. 1990. The arrow of time: A voyage through science to solve time’s greatest mystery. London: Flamingo.

By |

mathematics-1509559_1920

Mario Castagnino and Rafael Ferraro explain the differentiation between curved space-time, and the measurement of it by a clock. Whilst the physical parameters recorded by the clock are recorded as natural time, there is said to exist an infinite number of such parameters, all of which are defined as observer-dependent.

It is well known that there is a small confusion between a physical observer’s system and a geometrical coordinate system (or chart) in several papers. Of course they are two different concepts, e.g., in classical physics, an observer’s system is a rigid frame and a clock, where we can use all kinds of charts, for instance, Cartesian or polar coordinates. In curved space-time we cannot use a rigid frame and the natural generalization of the observer’s system will be a timelike fluid of observers, each one endowed with a clock, i.e., a set of timelike paths, each one with a different parameter, the “time” measured by the clock. This time is not necessarily the proper time; it is only an arbitrary continuous function of space-time. Of course we can describe this fluid of observers with any chart we like. We will find that physics is, in fact, observer dependent, but it is of course, chart independent. We shall restrict ourselves to irrotational fluid; thus we can define a set of orthogonal timelike hypersurfaces to the fluid paths, and we can define a parameter T, on each surface, such that the equations T = const would define the orthogonal hypersurfaces. We shall call this parameter a “natural time.” Of course, there exists an infinite set of natural times. We can pass from one to another via a continuous function T -> T’ = T'( T). We shall see that physics is independent of the natural time we use; it is only dependent on the chosen observer’s fluid. Of course, in general, natural time is different from proper time. We can label each fluid world line by three real parameters x1, x2 , x3 ,* and we can call x0 to the natural time T induced by the fluid of observers. Then x0, x1, x2, x3 is a chart and every event of space-time has its coordinates x0, x1, x2, x3 – namely, the space coordinates of the fluid world line, where the event happens, plus the natural time measured by the clock of this world line when the event happens. We shall call this chart an adapted chart (Castagnino and Ferraro 1988, 52-53).

Castagnino, Mario, and Ferraro, Rafael. 1988. “Toward a complete theory for unconventional vacua,” In Claudio Teitelboim (ed.) Quantum mechanics of fundamental systems 1, 51-62. New York: Springer Science+Business Media.

By |

wallpaper-1492818_1920.jpg

Friedel Weinert instructs that in order to comprehend why physical, natural time, is different from human, social time, it must be appreciated that natural units of time pre-exist conventional units of time. Furthermore, Weinert notes how socially convened units of time are based on natural temporalities.

In order to grasp the distinction between physical and human time, it is important to distinguish natural and conventional units of time. Natural units of time are based on periodic processes in nature, which recur after a certain interval. They may be quite imprecise, like the periodic flooding of the Nile, on which the ancient Egyptians based their calendar year; or more regular, like celestial phenomena. Some basic units of time, like the day and the year, are based on natural units of time. For instance, the equatorial rotational period of the Earth is 23 h 56 min and 4.1 s; that of Uranus is 17 h (Zeilik 1988, 508). The tropical year—the time that the Earth needs for one revolution around the sun—has a length of 365, 242,199… days or 365 days, 5 h, 48 min and 46 s (see Moyer 1982; Clemence 1966). But the calendar year has 365 days and 366 in leap years, which gives the calendar year an average length of 365.2425 days. As calendar years cannot have fractional lengths, there will always be a discrepancy between the tropical and the calendar year. This difference led to the replacement of the Julian calendar by the Gregorian calendar (1582). The Gregorian calendar will remain accurate to within one solar day for some 2,417 years. One difficulty with the day and the year, as just defined, is that these units of time are not constant, due to slight irregularities in the motion of the Earth. Historically, this discrepancy has led to calendar reforms and redefinitions of the ‘second’ from a fraction of the rotational period of the Earth around the sun to atomic oscillations.

Whilst physical time is based on such natural units, human time is based on conventional units of time. The 7-day week, introduced by the Romans, the subdivision of the day into 24 h, of the hour into 60 min and of minutes into 60 s, the division of the year into 12 months and the lengths of the months into 30 or 31 days (except February), again introduced by the Romans, are all conventional units of time. They are conventional because they respond to human social needs about time reckoning although there may be no physical processes, to which they correspond. To give an example, the beginning of the year (1st January) is purely conventional, since there is no natural event, which would single out this particular date. Equally the beginning of the day at midnight is a convention. Note, however, that not all such conventions are arbitrary. The equinoxes, the summer and winter solstices correspond to particular positions of the Earth with respect to the sun. Already the Babylonians introduced the 7-day week and named the days of the week, like the Egyptians, according to the sun and the known planets: moon, Mars, Mercury, Jupiter, Venus and Saturn (Wendorff 1985, 118). The division of the year into 12 months (4000 B.C.) was inspired by the 12 orbits of the moon around the Earth in one tropical year. But this creates a problem of time reckoning because the time between lunar phases is only 29.5 Earth days (Zeilik 1988, 152; Wendorff 1985, 14), but the solar year has 12.368 lunar months. As a consequence, the length of the month is now purely conventional and no longer related to the lunar month. The division of the day into 2 9 12 h is explained by geometrical considerations. During the summer only 12 constellations can be seen in the night sky, which led to the 12 h division of day and night. According to the sexagesimal system, there are 10 h between sunrise and sunset, as indicated by a sundial, to which 2 h are added for morning and evening twilight (see Whitrow 1989, 28–29; Wendorff 1985, 14, 49). When the year and the day are set to start also depends on conventions and social needs. In ancient Egypt, for instance, the year began on July 19 (according to the Gregorian calendar), since this date marked the beginning of the flooding of the Nile (Wendorff 1985, 46). In the late Middle Ages there existed a wide variety of New Year’s days: Central Europe (December 25); France (March 21; changed to 1st January in 1567); British Isles, certain parts of Germany and France (March 25) (Wendorff 1985, 185; Elias 1988, 21f).

Despite these aspects of conventionality, it must be emphasized that the conventional units of time must keep track of natural units of time. For otherwise, conventional units of time will fall out of step with the periodicity of the natural units. The measurement of time is inseparably connected with the choice of certain inertial reference frames, like the ‘fixed’ stars, the solar system, and the expansion of galaxies or atomic vibrations (Clemence 1966, 406–409). It was one of the great discoveries of Greek philosophy to have realized that there exists a link between time and cosmology. The existence of conventional units of time thus presupposes the existence of natural units of time (Weinert 2013, 16-17).

Weinert, Friedel. 2013. The march of time: Evolving conceptions of time in the light of scientific discoveries. Berlin and Heidelberg: Springer-Verlag.