The exact time in days. How many hours are there in a day. Day sunny and starry

How long is a day? It's a strange question: we know from childhood that a day is exactly 24 hours, or 1440 minutes, or 86400 seconds. So, but not so. A day is a period of time during which the Earth makes one complete turn around its axis, but it turns out to never take exactly 24 hours.

How long is a day?

If we take a distant star as a starting point, and count the interval for which it will return to the same point in days, it turns out that one revolution of our planet takes 23 hours 56 minutes and 4 seconds! That is, in a day, the astronomical midnight can crawl away by almost 4 minutes! Moreover, this period, called sidereal days, depending on the friction caused by synoptic situations, ebbs / flows and geological events, changes all the time in the range of up to 50 seconds. If we take our Sun as a starting point, as our ancestors did, then the number is already closer to 24 hours. This is called a solar day. On average per year, taking into account the planet's turnover around the sun sunny day is a fraction of a second shorter than twenty-four hours.

When these discrepancies were revealed with the help of the most accurate atomic clocks, it was decided to redefine the second as a fixed fraction of the "solar" day, more precisely, one million six hundred or forty thousandth.

The new second came into use in 1967 and is defined as "a time interval equal to 9 192 631 770 periods of radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom in the absence of disturbance by external fields." You can’t say more precisely - it’s just too dreary to say all this at the end of a long day.

The new definition of the second means that solar days are gradually shifting in relation to atomic ones. As a result, scientists had to introduce the so-called "leap second" (or "coordination second") into the atomic year in order to match the atomic year with the solar one.

Since 1972, the leap second has been added 23 times. Imagine, otherwise our day would have increased by almost half a minute. And the Earth continues to slow down its rotation. And, according to scientists, in the XXIII century there will be 25 current hours in our day.

"Leap second" was last added on December 31, 2005 at the direction of the International Earth Rotation and Coordinate Estimation Service, based at the Paris Observatory.

Good news for astronomers and those of us who love it when the clock keeps pace with the movement of the Earth around the Sun, but headache for computer programs and all the equipment that is on space satellites.

The idea of introducing a "leap second" was strongly opposed by the International Telecommunications Union, which even made a formal proposal to completely cancel it back in December 2007.

You can, of course, wait until the difference between Coordinated Universal Time (UTC) and Greenwich Mean Time (GMT) reaches exactly one hour (somewhere in 400 years) and then everything is put in order. In the meantime, the debate over what is considered "real" time continues.

How long is a day?

If we take a distant star as a starting point, and count the interval for which it will return to the same point in days, it turns out that one revolution of our planet takes 23 hours 56 minutes and 4 seconds! That is, in a day, the astronomical midnight can crawl away by almost 4 minutes! Moreover, this period, called sidereal days, depending on the friction caused by synoptic situations, ebbs / flows and geological events, changes all the time in the range of up to 50 seconds. If we take our Sun as a starting point, as our ancestors did, then the number is already closer to 24 hours. This is called a solar day. On average, for a year, taking into account the planet's revolution around the sun, a solar day is a fraction of a second shorter than twenty-four hours.

"Leap second" was last added on December 31, 2005 at the direction of the International Earth Rotation and Coordinate Estimation Service, based at the Paris Observatory.

Good news for astronomers and those of us who love it when clocks keep pace with the movement of the Earth around the Sun, but a headache for computer programs and all the hardware that is on space satellites.

The idea of introducing a "leap second" was strongly opposed by the International Telecommunications Union, which even made a formal proposal to completely cancel it back in December 2007.

August 10, 2016

How long is a day? You probably think that exactly 24 hours? Depends on the circumstances. A day is a period of time during which the Earth makes one turn around its axis.

So how long is a day?

In fact, one rotation of the Earth on its axis is never exactly twenty-four hours.

There are 23 hours 56 minutes and 4 seconds in a day. All my life I have lived in a lie!

Amazingly, this indicator can fluctuate in one direction or another for as much as fifty seconds! This is because the speed of the Earth's rotation changes all the time - due to friction caused by synoptic situations, ebb / flow and geological events.

On average, a day is a fraction of a second shorter per year than twenty-four hours.

When these discrepancies were revealed with the help of atomic clocks, it was decided to redefine the second as a fixed fraction of the "solar" day, more precisely, one million six hundred or forty thousandth.

"Leap second" was last added on December 31, 2005 at the direction of the International Earth Rotation and Coordinate Estimation Service, based at the Paris Observatory.

The idea of introducing a "leap second" was strongly opposed by the International Telecommunications Union, which even made a formal proposal to completely cancel it back in December 2007.

Earth day- this is the time during which the Earth rotates around its axis, and the cycle "day-night" changes. Our life is subject to this cycle. In the morning we go to work, in the evening we go to bed. The corresponding cyclic physiological processes in living organisms are called biological rhythms (biorhythms)... For example, the minimum body temperature in humans occurs early in the morning, and the maximum - in the evening. With severe purulent infections, the temperature difference in the morning and evening reaches 3-4 degrees Celsius.

It seems to me that for most city people 24-hour biorhythm is forced and violent as evidenced by the regular use of the alarm clock. However, you can train yourself to go to bed and get up at the same time of day. If our day is lengthened (for example, the autumn shift of the clock hands), it is easier to endure than when it is shortened in the spring, when you have to get up an hour earlier.

How many hours will a day last for a person who lives "out of time", that is, having no opportunity to determine the time of day by outward signs? These months-long experiments, including on himself, are described by French caver(from the Greek spelaion - cave) in his book “ IN THE ABOUT LAND"Published in Moscow in 1982... Of course, the material given below cannot be considered an exhaustive overview of the accumulated world experience in biorhythmology, this is just curious information for thought.

The experiments described in the book were carried out from 1964 to 1972 in deep caves on the border of Italy and France, as well as in the United States. The caves are comfortable with their constant climatic conditions: silence, complete absence of wind and sunlight, constant temperature and humidity. Experienced volunteer speleologists took part in the experiments. A cave is more natural natural environment full of dangers (abysses, cold, dampness, darkness, rare insects and even mice) compared to a specially built bunker.

Why was it necessary? Not only for the sake of "naked" science. In the 1960s, space was actively explored, long-term expeditions to other planets were planned, and NASA was interested in long-term experiments on the effect of isolation of people on their livelihoods. The French military department even became interested in the results of the experiments. Why you are interested - you will find out below.

Is it easy to live in a cave for months? No. If you are able not to communicate with anyone for 2-3 days without suffering from a communication deficit, then you might have succeeded. In their free time, cavers read books (they all had artificial lighting), took up hobbies (drawing, photography), explored their cave. But every day they had a whole list of boring, obligatory tasks: calls "upstairs" about each event (awakening, eating, physiological departures, going to bed), a number of annoying psychophysiological tests for composure, work ability, reaction speed, etc. In addition, in a number of experiments I had to constantly wear sensors, which in those days were not always portable, so the volunteers were in the cave like dogs on a leash several meters away. And the sensor electrodes irritated the skin. Every day I had to collect and send up urine and feces tests... Even the composition of the bristles shaved off the face was analyzed. Cavers led in caves diary, where they wrote down the subjective date and their feelings. The real date was known only to the top in the escort team. There was not always enough money for these lengthy experiments, but all the participants held on very steadfastly, despite the difficulties. Due to the lack of money for food during the experiment in the United States, the escort group even caught and ate rattlesnakes.

Brief Results of Timeless Experiments

1) in 1964-1965 parallel individual experiments took place Antoine Senny(4 months, male 35 years old) and (3 months, female 25 years old). In those days, such a length of solitary stay in a cave was an unattainable record, especially among women.

Antoine Senny (Tony):

when Tony counted aloud to 120 in order to subjectively measure the interval of 2 minutes, it really took from 3 to 4 minutes.

From the first month of the experiment, a violation of the rhythm of wakefulness and sleep was found in Antoine Senny. His day sometimes lasted 30 hours in a row, and the duration of sleep several times exceeded 20 hours. This gave cause for concern.

He especially impressed us when, for 22 days the length of his day ranged from 42 to 50 hours (average 48 hours), with fantastically long periods of continuous activity ranging from 25 to 45 hours (average 34 hours) and with sleep durations ranging from 7 to 20 hours. We discovered a phenomenon that we named in 1966 two-day rhythm, that is, a duration of about 48 hours.

On the 61st day of this exceptional experiment, Tony made us seriously worried: he slept for 33 hours. I was already afraid for his life and was preparing to go down to him, when suddenly I heard phone call: Tony informed me that he had a good night!

So the average duration Tony's sleep at a 48-hour rhythm was 12 hours... His daily cycle consisted of 36 hours of wakefulness and 12 hours of sleep, but this pattern was violated several times: Senny could sleep for 30 hours, and then only 18 hours remained for the active period. Therefore, in 1965 Ministry of War of France decided to study in more detail the nature of this sleep, which so significantly increases a person's working capacity and gives the body tremendous opportunities for recuperation. Such experiments were carried out in 1968-1969 (further on this page see experiment No. 3).

2) in 1966 passed a record experiment Jean-Pierre Merete- "human laboratory" (6 months).
This volunteer had perhaps the hardest time. He lived almost all the time with sensors that recorded the electrical activity of his brain, eye movements, muscle tone, heart and breathing rhythms, body and skin temperature. The electrodes irritated the skin to the point of bleeding, but every time Mereta was persuaded to “be patient a little longer” for the sake of science, and each time he agreed.

Merete woke up and went to bed every day two to three hours later than the previous day... In this study, using electroencephalograms recorded during sleep, the presence of the subject has a 48-hour biorhythm.

During the first 10 days of life in a cave, Merete's daily rhythm was approximately 25 hours(15 hours of wakefulness + 10 hours of sleep), which almost corresponded to the normal rhythm. Then during next month his body followed a rhythm for about 48 hours(34 hours of waking and 14 hours of sleep).

The following months surprised again: Merete's rhythm became inconsistent and ranged from 18 to 35 hours, with periods of activity from 12 to 20 hours and sleep from 7 to 15 hours. Sometimes he even slept 17 hours!

This irregularity of the rhythm (cycles were recorded without any rest lasting about 50 hours with an average duration of 25 hours) continues to attract the interest of specialists. This is undoubtedly one of the most important results of Jean-Pierre Merete's experiment.

3) in 1968-1969- voluntary confinement Philip Englander and Jacques Chabert(4.5 months each).

The first volunteer (Philip Englender, 30) had to live for 2 months with 48 hour days, and the second (Chabert, 28 years old) had to live 3 months with a constant bright electric light(500 W).

Philip Englender:

Philip Englander's usual 24-hour rhythm, 2 weeks after the start of the experiment, was independently replaced by a 48-hour rhythm, which lasted 12 days. Then, according to a plan drawn up in conjunction with French military experts, an attempt was made to consolidate this spontaneously arising 48-hour cycle for another 2 months and to achieve this with the help of a bright 500 W lamp, which should burn over his transparent tent for 34 hours all days. Of course, Phillippe did not know how long this lamp would burn each time.

The attempt was a success. First a person lived in a world where the day was doubled: 36 hours of wakefulness and only 12 hours of sleep, without any disturbance. Philip, as shown by numerous electroencephalograms of his sleep, perfectly adapted to this regime.

In the end, Philip was given the opportunity to live at his own discretion, as in the initial period of the experiment. Something amazing happened to the researchers. Philip, instead of going back to the 24 hour rhythm, continued without the slightest effort keep a 48 hour rhythm wakefulness and sleep. So when it was announced to him that it was already January 4, he exclaimed:

Wow! I missed New Year! I thought it was just the beginning of November!

Jacques Chabert:

Jacques, in contrast to Phillippe, kept a biological time count close to real days: the intervals between his awakenings averaged 28 hours... Jacques liked the bright lights; his sleep was not disturbed in the least. Only on the third month of complete loneliness did his day become equal to 48 hours, which was accompanied by increased physical activity (in particular, during this period he conducted intensive exploration in the cave).

Subjectively, for Jacques, 105 days passed between his descent and emergence to the surface instead of the real 130 days. Before the experiment, Jacques had read something on the topic of determining the true length of time, so he was better guided by the number of days passed than his neighbor Phillippe.

Eventually, Jacques and Philippe's organisms gave way and obeyed the 48-hour rhythm. He gave a great advantage: 2 hours won every day... If a common person sleeps 8 hours out of 24, then with a 48-hour rhythm, only 12 hours out of 48 are enough for sleep.

Philip was a keen speleologist. He explored his cave and left these lines in his diary: “Digging, clearing, carving steps, I often depleted myself, working 4-5 hours without interruption". But, as was then calculated on the surface, he worked for more than 20 hours!

The experiments of Chabert and Englander have undergone a lengthy analysis. They allowed select people who can live the 48-hour rhythm... Michel Sifre writes that the criteria for this selection have already been developed.

4) in 1972- (6 months).

During the entire 2-month experiment in 1962, Sifra's subjective days were close to normal and equaled on average 24 hours 31 minutes, differing from the real ones by half an hour.

In 1972, in contrast, the subjective days increased significantly more: during the first 1.5 months, each day was 2 real hours longer (26 hours).

Then, for 2 weeks, the rhythm of wakefulness and sleep was unstable: 48-hour days alternated with 28-hour days (their average duration was 37 hours).

Thus, in 1962, Sifru needed 9.5 hours sleep to be awake for 15 hours; and in 1972 he had enough 7.5 hours of sleep at 28 hours of wakefulness.

Then, for several months, the cycle was close to 28 hours, after which this rhythm again became 2-day, but without regularity: 48-hour days for 2 weeks alternated with 28-hours. Finally, until the very end of the experiment, it stabilized at 28 hours.

Michel Sifre was also hung with sensors, including measuring rectal body temperature(in the rectum). Analysis showed that before descending into the cave, it was minimum at 2 am(1.5 hours after falling asleep). In the cave, the minimum temperature each time came about 1 hour later - at 3, 4 and 5 o'clock in the morning, etc., so that after 2 weeks "out of time" the minimum value appeared on the curve at 3 o'clock in the afternoon. And so it was repeated several times during the experiment.

These are the results over 10 years received by a group of researchers led by Michel Sifre. None of the cavers days were not shortened... For all, they only lengthened. Perhaps, this is precisely the desire of students to go to bed in the morning and stay awake at night?

Speaking about optimal daily biorhythms, one cannot but recall Leonardo da Vinci... They say that he slept only 1.5 hours a day. The secret of his enormous capacity for work is that he fell asleep for 15 minutes every 4 hours.

Melatonin

A special hormone is produced in the human body melatonin, which is responsible for adapting to biorhythms and falling asleep... Melatonin is produced pineal gland (pineal gland) and improves the quality of sleep, reduces the frequency of attacks of headaches, dizziness, improves mood. It speeds up falling asleep, reduces the number of nighttime awakenings, improves well-being after waking up in the morning, does not cause a feeling of lethargy, weakness and fatigue upon awakening. Makes dreams more vivid and emotionally rich. The body adapts to the rapid change of time zones, reduces stress reactions, and regulates neuroendocrine functions. Shows immunostimulating and antioxidant properties.

Most of all melatonin is formed in the dark, an excess of light is destructive for him. At night, 70% of the daily melatonin is formed.

Exists melatonin preparations for oral administration. Sold in Belarus MELAXEN and VITA-MELATONIN... They are assigned when desynchronosis(violation of the normal circadian rhythm, for example, when flying between different time zones), sleep disorders, depression. The drugs are not the cheapest, but, in principle, affordable.

(The last part of the article about the influence of lunar cycles on miners and the Montauk experiment was eventually deleted on 01/30/2016 at the request of readers as pseudoscientific)