«The time is the fabric of the life. » Benjamin Franklin The notion of existence and of time are intimately linked. Man exists in time, his life flowing with him.
But for some, the time is a simple variable and for others an illusion.
Leibniz was right and Newton wrong, time is not absolute but relative as Einstein has shown it.
It flows more slowly at high speeds or in the vicinity of supermassive celestial objects.
But is it one-way or is it reversible? Can it be abolished under certain circumstances?
9. Flow
We regularly observe the effect of time on ourselves, on other living beings and on the inert world.
On our scale, death illustrates the irreversibility of time, yet our perception of time is subjective.
Time measurement
By observing the course of the sun, moon, and seasons, the humans learned early on how to cut time, first by day, then by month, and finally by year.
To measure durations is to determine rhythms, to count
oscillations, to subdivide time.
Circadian rhythm
All living beings follow a circadian rhythm of 24 hours.
It is an internal clock that gives the tempo, regulating our physiology throughout the body at all levels.
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Located at the base of the brain, the hypothalamus* regulates major biological functions and coordinates peripheral clocks.
It controls digestion, vascularization, sweating, heartbeat, body temperature and sleep.
Sensitive to light, the hypothalamus connects the autonomic nervous system and the endocrine system indirectly controlling the production of melatonin and cortisol.
Sleep-wake cycle.
During sleep, the melatonin is secreted by the pineal gland; conversely, the cortisol is produced during the awakening phase by the adrenal glands.
The melatonin retroactiving on the hypothalamus and the
cortisol on secondary brain clocks.
A protein encoded by the Period gene has its rate following a 24-hour cycle thus participating in the regulation of waking and sleeping periods.
Dopamine
The impression of time flow varies with the rhythm of life, it depends on the dopamine level, high: the time slows down.
By the age of 20 years, the production of the neurotransmitter decreases, so time seems to go faster for the elderly.
Period
Many behavioural and physiological processes are cyclical and last 3 seconds or 90 minutes.
3 seconds
The human mind divides the perception of time, images,
sounds in intervals of 3 seconds, which corresponds to the duration of a breath or short-term memory.
90 min
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Periods of activity, sleep cycles or the functioning of certain organs last 90 minutes.
As well as some of our scheduled activities: courses,
conferences, football match or film.
Summary
Humans learned very early to cut time, first in day, then in month and finally in year.
All living beings follow a rhythm of 24 hours, an internal clock giving the tempo.
The impression of the time flow varies with age and the life rhythm, it depends mainly on the dopamine level.
9.2 Reversibility
At the macroscopic level, the time seems to flow in only one direction. yesterday is gone and tomorrow to come: we live only in the present moment.
Yet the time arrow can be reversed: the second principle of thermodynamics does not speak of the impossibility of the time turn but rather of improbability.
The equations describing the movement of molecules are also reversible, provided that the number of atoms involved is limited.
Principles of Thermodynamics
The concept of energy is universal. In Greek energy means force in action, i.e., the ability to produce a movement.
First principle
The first principle of thermodynamics establishes that the total energy of a system is conserved and defines the relationship between the different forms it can take.
However, it does not set any limits for the direction in which these transformations take place.
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According to the first principle of thermodynamics, during any transformation, the internal energy variation of a system is equal to the sum of the heat transfer and work exchanged.
Second principle
On our scale, thermodynamic processes take place in only one direction: heat is transmitted from the hottest objects to the colder ones or else human beings do not rejuvenate…
The second principle of thermodynamics allows to define an arrow of the time distinguishing past and future, the entropy*
allowing to quantify it.
The entropy of an isolated system tends to increase and can never decrease, the systems spontaneously moving towards thermal equilibrium.
The second principle of thermodynamics therefore describes the direction in which natural processes take place.
Boltzmann paradox
In 1877, Boltzmann gives a probabilistic evolution to the transition from microscopic to macroscopic, the entropy
becoming a probability measure of the system stability.
In the current situation, an irreversible process takes place where the low entropy of microscopic states tends towards complex systems at higher entropy.
The reversal of equilibrium speeds, ensuring the return to a state of non-equilibrium, is however possible.
But only for microscopic situations resulting in an initial unbalanced state. According to Boltzmann these particular situations are on the whole extremely rare.
Summary
The reverse evolution of time is possible but is all the more unlikely as the systems are complex.
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There is a type of particle correlation defying the general definitions of the distance and the time.
In the quantum entanglement the concept of space-time being no longer necessary can be abolished.
Quantum entanglement
The quantum entanglement is one of the most troubling
phenomena of the quantum mechanics, if not in the universe.
Two particles - or two quantum systems – separate remain entangled forming an indivisible whole, regardless of the distance between them.
The observation of a particle property will instantly cause a correlated modification of the other, even if they are several million light-years apart.
Summary
Once two particles are entangled their destinies are linked irremediably.
They form an inseparable whole regardless of the distance and the time scale.
9.4 Conclusion
All living beings follow a rhythm of 24 hours, an internal clock giving tempo to the whole organism.
The impression of the time flow varies with age and depends mainly on the dopamine level.
The reverse evolution of time is possible but is all the more unlikely as the systems are complex.
Two quantum particles separate remain entangled and their destinies irreparably linked regardless of distance and time, they form an inseparable whole.
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