Maximum low tide. Ebbs and flows, the essence of the phenomenon of ebbs and flows

The world's oceans live by their own rules, which are harmoniously combined with the laws of the universe. For a long time, people noticed that they were actively moving, but could not understand what was causing these fluctuations in sea level. Let's find out what the ebb and flow is?

Ebbs and flows: mysteries of the ocean

The sailors knew very well that the ebb and flow of tides is a daily phenomenon. But neither ordinary residents nor scientific minds could understand the nature of these changes. As early as the fifth century BC, philosophers tried to describe and characterize how the World Ocean moved. seemed something fantastic and extraordinary. Even reputable scientists considered the tides to be the breathing of the planet. This version has existed for several millennia. It was only at the end of the seventeenth century that the meaning of the word "tide" was associated with the movement of the Moon. But to explain this process with scientific point vision was never achieved. Hundreds of years later, scientists figured out this mystery and gave precise definition daily changes in water level. The science of oceanology, which emerged in the twentieth century, established that the tide is the rise and fall of the water level of the World Ocean due to the gravitational influence of the Moon.

Are the tides the same everywhere?

The influence of the Moon on the earth's crust is not the same, so it cannot be said that the tides are identical all over the world. In some parts of the planet, daily sea level changes reach sixteen meters. And residents of the Black Sea coast practically do not notice the ebbs and flows at all, since they are the most insignificant in the world.

Usually the change occurs twice a day - in the morning and in the evening. But in the South China Sea, the tide is a movement water masses, which occurs only once every twenty-four hours. Sea level changes are most noticeable in straits or other narrow places. If you observe, you will notice with the naked eye how quickly the water leaves or comes in. Sometimes it rises five meters in a few minutes.

As we have already found out, changes in sea level are caused by the impact on the earth’s crust of its constant satellite, the Moon. But how does this process happen? To understand what a tide is, it is necessary to imagine in detail the interaction of all the planets in the solar system.

The Moon and Earth are in constant dependence on each other. The Earth attracts its satellite, which, in turn, tends to attract our planet. This endless rivalry allows us to maintain between the two cosmic bodies required distance. The Moon and Earth move in their orbits, sometimes moving away and sometimes approaching each other.

At the moment when the Moon comes closer to our planet, the earth's crust bends towards it. This causes the water to ripple on the surface earth's crust, she seems to be trying to rise higher. Distance earth's satellite causes a decline in sea levels.

Tidal interval on Earth

Since the tide is a regular phenomenon, it must have its own specific interval of movement. Oceanologists were able to calculate exact time lunar days. This term is usually used to describe the Moon’s revolution around our planet; it is slightly longer than the twenty-four hours we are used to. Every day the tides shift by fifty minutes. This time period is necessary for the wave to “catch up” with the Moon, which moves thirteen degrees during the Earth’s day.

The influence of ocean tides on rivers

We have already found out what a tide is, but few people know about the influence of these ocean fluctuations on our planet. Surprisingly, even rivers are influenced by the ocean tides, and sometimes the results of this interference can be incredibly frightening.

During high tides, a wave entering the river mouth meets the flow fresh water. As a result of the mixing of water masses various densities a powerful shaft is formed, which enormous speed begins to move against the flow of the river. This flow is called boron, and it is capable of destroying almost all living things in its path. Similar phenomenon in a few minutes, it washes away coastal settlements and erodes the coastline. Bor stops as suddenly as it started.

Scientists have recorded cases when a powerful boron turned rivers back or stopped them completely. It is not difficult to imagine how catastrophic these phenomenal events of tidal action became for all the inhabitants of the river.

How do tides affect marine life?

No wonder the tides have an effect a huge impact for all organisms that live in the depths of the ocean. The hardest thing is for small animals living in coastal zones. They are forced to constantly adapt to changing water levels. For many of them, the tides are a way to change their habitat. During high tides, small crustaceans move closer to the shore and find food for themselves; the ebb wave pulls them deeper into the ocean.

Oceanologists have proven that many marine life are closely related to tidal waves. For example, some species of whales have a slower metabolism during low tides. In other deep-sea inhabitants, reproductive activity depends on wave height and amplitude.

Most scientists believe that the disappearance of phenomena such as fluctuations in the level of the World Ocean will lead to the extinction of many living beings. Indeed, in this case they will lose their power source and will not be able to adjust their The biological clock to a certain rhythm.

Earth's rotation speed: is the influence of tides significant?

For many decades, scientists have been studying everything related to the term “tide”. This is a process that brings more and more mysteries every year. Many experts associate the speed of the Earth's rotation with the action of tidal waves. According to this theory, under the influence of tides they are formed. On their way, they constantly overcome the resistance of the earth's crust. As a result, the planet’s rotation speed slows down, almost imperceptibly for humans.

By studying sea corals, oceanologists found that several billion years ago the earth's day was twenty-two hours. In the future, the rotation of the Earth will slow down even more, and at some point it will simply become equal to the amplitude of the lunar day. In this case, as scientists predict, the tides will simply disappear.

Human life activity and the amplitude of oscillations of the World Ocean

It is not surprising that humans are also susceptible to the effects of tides. After all, it consists of 80% liquid and cannot help but respond to the influence of the Moon. But man would not be the crown of nature’s creation if he had not learned to use almost everything to his advantage. natural phenomena.

The energy of a tidal wave is incredibly high, so for many years various projects have been created to build power plants in areas with a large amplitude of movement of water masses. There are already several such power plants in Russia. The first was built in the White Sea and was an experimental option. The power of this station did not exceed eight hundred kilowatts. Now this figure seems ridiculous, and new power plants using tidal waves are generating energy that powers many cities.

Scientists see the future in these projects Russian energy, because they allow you to treat nature more carefully and cooperate with it.

Ebbs and flows are natural phenomena that, not so long ago, were completely unexplored. Each new discovery by oceanographers leads to even greater questions in this area. But perhaps one day scientists will be able to unravel all the mysteries that the ocean tide presents to humanity every day.

The phenomenon of sea tides has been noticed since ancient times. Herodotus wrote about tides back in the 5th century BC. For a long time people could not understand the nature of tides. Various fantastic assumptions have been made, such as that the Earth breathes. Even the famous scientist (1571-1630), who discovered the laws of planetary motion, considered the ebb and flow of tides as a result... of the breathing of planet Earth.

The French mathematician and philosopher (1596-1650) was the first among European scientists to point out the connection between tides and tides, but did not understand what this connection was. Therefore, he gave such an explanation for the phenomenon of tide that is so far from the truth: the Moon, revolving around the Earth, puts pressure on the water, causing it to go down.

Gradually, scientists figured out this, it must be said, difficult problem, and it was found that tides are a consequence of the influence of the gravitational forces of the Moon and (to a lesser extent) the Sun on the surface of the ocean.

In oceanology the following definition is given: The rhythmic rise and fall of water, as well as the accompanying currents, are called tides.

Tides occur not only in the ocean, but also in the atmosphere and the earth's crust. The uplift of the earth's crust is very insignificant, so they can only be determined with special instruments. Another thing is the water surface. Particles of water move, and, receiving acceleration from the Moon, approach it incomparably more than the earth's firmament. Therefore, on the side facing the Moon, the water rises up, forming a bend, a kind of water mound on the surface of the ocean. As the Earth rotates on its axis, this mound of water moves along the surface of the ocean following.

Theoretically, even distant stars participate in the formation of tides. But this remains a purely theoretical proposition, since the influence of stars is negligible and can be neglected. More precisely, it is impossible to neglect it, since there is nothing to neglect. The impact of the Sun on the surface of the ocean due to the great distance of the star is 3-4 times weaker than the impact of the Moon. Powerful lunar tides mask the attraction of the Sun and therefore solar tides as such are not observed.

The extreme position of the water level at the end of the tide is called full of water, and at the end of low tide - low water.

Two photographs taken from the same point at moments of low and high water,
give an idea of tidal level fluctuations.

If we start observing the tide at the moment of high water, we will see that after 6 hours the lowest water level will occur. After this, the tide will begin again, which will also continue for 6 hours until it reaches its highest level. The next high tide will occur 24 hours after the start of our observation.

But this will only happen under ideal, theoretical conditions. In reality, during the day there is one high and one low tide - and then the tide is called diurnal. Or it may happen in two tidal cycles. In this case we are talking about a semidiurnal tide.

The period of daily tide does not last 24 hours, but 50 minutes longer. Accordingly, the semi-diurnal tide lasts 12 hours and 25 minutes.

The World Ocean experiences predominantly semidiurnal tides. This is declared by the rotation of the Earth around its axis. The tide, like a huge gentle wave whose length is many hundreds of kilometers, spreads across the entire surface of the World Ocean. The period of occurrence of such a wave varies in each place of the ocean from half a day to a day. Based on the frequency of the onset of tides, they are distinguished as diurnal and semidiurnal.

During full turn The Earth moves around its axis by about 13 degrees across the sky. It takes a tidal wave just 50 minutes to “catch up” with the Moon. This means that the time of arrival of full water in the same place in the ocean constantly shifts relative to the time of day. So, if today there was high water at noon, then tomorrow it will be at 12 hours 50 minutes, and the day after tomorrow at 13 hours 40 minutes.

IN open ocean, where the tidal wave does not meet resistance from continents, islands, bottom irregularities and coastlines, mostly regular semidiurnal tides occur. Tidal waves in the open ocean are invisible, where their height does not exceed one meter.

The tide manifests itself in full force on the open ocean coast, where for tens and hundreds of miles, neither islands nor sharp bends of the coastline are visible.

When the Sun and Moon are located on the same line on one side of the Earth, the gravitational force of both luminaries seems to add up. This happens twice during the lunar month - on the new moon or full moon. This position of the luminaries is called syzygy, and the tide occurring on these days is called. Spring tides are the highest and most powerful tides. In contrast, the lowest tides are called .

It should be noted that the level of spring tides in the same place is not always the same. The reason is still the same: the movement of the Moon around the Earth and the Earth around the Sun. Let's not forget that the Moon's orbit around the Earth is not a circle, but an ellipse, creating a fairly noticeable difference between the perigee and apogee of the Moon - 42 thousand km. If during syzygy the Moon is at perigee, that is, at the shortest distance from the Earth, this will cause a high tidal wave. Well, if during the same period the Earth, moving in its elliptical orbit around the Sun, finds itself at the smallest distance from it (and coincidences also occur occasionally), then the ebb and flow of the tides will reach their maximum magnitude.

Here are some examples showing the maximum height that ocean tides reach in specific locations globe(in meters):

Name	Location	Tide height (m)
Mezen Bay White Sea
Estuary of the Colorado River
Penzhinskaya Bay of the Sea of Okhotsk
Mouth of the Seoul River	South Korea
Fitzroy River Estuary	Australia
Grenville
Mouth of the Koksoak River
Port Gallegas	Argentina
Bay of Fundy

During high tide, water rises at different speeds. The nature of the tide largely depends on the angle of inclination of the seabed. On steep banks, the water rises slowly at first - 8-10 millimeters per minute. Then the speed of the tide increases, becoming greatest at the “half-water” position. Then it slows down to the position of the upper limit of the tide. The dynamics of low tide are similar to the dynamics of high tide. But the tide looks completely different on wide beaches. Here the water level rises very quickly and is sometimes accompanied by a high tidal wave rushing rapidly along the shallows. Swimming enthusiasts who have been gaping at such beaches cannot expect anything good in these cases. The sea element does not know how to joke.

In inland seas, fenced off from the rest of the ocean by narrow and shallow winding straits or clusters of small islands, the tides arrive with barely noticeable amplitudes. We see this in the example of the Baltic Sea, which is reliably closed from the tides by shallow waters. Danish Straits. Theoretically, the tide height in the Baltic Sea is 10 centimeters. But these tides are invisible to the eye; they are hidden by fluctuations in water level due to wind or changes atmospheric pressure.

It is known that in St. Petersburg there are often floods, sometimes very strong. Let us remember how vividly and truthfully he conveyed the drama of the severe flood of 1824 in the poem “ Bronze Horseman» the great Russian poet A.S. Pushkin. Fortunately, floods of such magnitude in St. Petersburg have nothing to do with tides. These floods are caused by cyclone winds, which significantly raise the water level by 4–5 meters in the eastern part of the Gulf of Finland and in the Neva.

Ocean tides have even less impact on the inland seas of the Black and Azov, as well as the Aegean and Mediterranean. In the Sea of Azov, connected to the Black Sea by a narrow Kerch Strait, the tidal amplitude is close to zero. In the Black Sea, fluctuations in water level under the influence of tides do not reach even 10 centimeters.

Conversely, in bays and narrow bays that have free communication with the ocean, the tides reach significant levels. Freely entering the bay, tidal masses rush forward, and, not finding a way out among the narrowing shores, rise up and flood the land over a large area.

During ocean tides, a dangerous phenomenon called boron. Flow sea water, entering the river bed and meeting the river flow, it forms a powerful foamy shaft, rising like a wall and rapidly moving against the flow of the river. On its way, the boron erodes the banks and can destroy and sink any ship if it ends up in the river channel.

On greatest river South America In the Amazon, a powerful tidal wave 5-6 meters high passes at a speed of 40–45 km/h at a distance of up to one and a half thousand kilometers from the mouth.

Sometimes tidal waves stop the flow of rivers and even turn them in the opposite direction.

On the territory of Russia, rivers flowing into the Mezen Bay of the White Sea experience a small boron.

In order to use tidal energy, tidal power stations have been built in some countries, including Russia. The first tidal power plant, built in the Kislogubskaya Bay of the White Sea, had a capacity of only 800 kilowatts. Subsequently, PES were designed with a capacity of tens and hundreds of thousands of kilowatts. This means that the tides begin to work to the benefit of a person.

And lastly, but globally important, about tides. Currents caused by tides encounter resistance from continents, islands and the seabed. Some scientists believe that as a result of friction of water masses against these obstacles, the rotation of the Earth around its axis slows down. At first glance, this slowdown is quite insignificant. Calculations have shown that over the entire period of our era, that is, over 2000 years, days on Earth have become longer by 0.035 seconds. But what was the calculation based on?

It turns out that there is evidence, albeit indirect, that the rotation of our planet is slowing down. While studying extinct corals of the Devonian period, the English scientist D. Wells discovered that the number of daily growth rings is 400 times greater than the annual ones. In astronomy, the theory of stability of planetary movements is recognized, according to which the length of the year remains practically unchanged.

It turns out that in the Devonian period, that is, 380 million years ago, the year consisted of 400 days. Consequently, the day then had a duration of 21 hours and 42 minutes.

If D. Wells was not mistaken when calculating the daily rings of ancient corals, and if the rest of the calculations are correct, then everything goes to the point that in less than 12–13 billion years the earth’s day will become equal in length to the lunar month. And then what? Then our Earth will constantly face one side towards the Moon, as is currently the case with the Moon in relation to the Earth. The rising waters will stabilize on one side of the Earth, the tides will cease to exist, and the solar tides are too weak to be felt.

We provide our readers with the opportunity to independently evaluate this rather exotic hypothesis.

Ebbs and flows are called periodic increases and decreases in water levels in the oceans and seas.

Twice during the day with an interval of about 12 hours 25 minutes water near the ocean shore or open sea rises and, if there are no obstacles, sometimes floods large spaces - this is a tide. Then the water drops and recedes, exposing the bottom - this is low tide. Why is this happening? Even ancient people thought about this, and they noticed that these phenomena are associated with the Moon. I. Newton was the first to point out the main reason for the ebb and flow of the tides - this is the attraction of the Earth by the Moon, or rather, the difference between the attraction of the Moon over the entire Earth as a whole and its water shell.

Explanation of the ebb and flow of tides by Newton's theory

The attraction of the Earth by the Moon consists of the attraction of individual particles of the Earth by the Moon. Particles in this moment those closer to the Moon are attracted by it more strongly, and those more distant - weaker. If the Earth were absolutely solid, then this difference in the force of gravity would not play any role. But the Earth is not absolutely solid body, therefore, the difference in the attractive forces of particles located near the surface of the Earth and near its center (this difference is called the tidal force) displaces the particles relative to each other, and the Earth, primarily its water shell, is deformed.

As a result, on the side facing the Moon and on its opposite side the water rises to form tidal ridges and excess water accumulates there. Due to this, the water level in other opposite points of the Earth decreases at this time - low tide occurs here.

If the Earth did not rotate, and the Moon remained motionless, then the Earth, along with its water shell would always maintain the same elongated shape. But the Earth rotates, and the Moon moves around the Earth in about 24 hours 50 minutes. With the same period, tidal peaks follow the Moon and move along the surface of the oceans and seas from east to west. Since there are two such projections, a tidal wave passes over each point in the ocean twice a day with an interval of about 12 hours and 25 minutes.

Why is the height of the tidal wave different?

In the open ocean, the water rises slightly when a tidal wave passes: about 1 m or less, which remains practically unnoticeable to sailors. But off the coast, even such a rise in water level is noticeable. In bays and narrow bays, the water level rises much higher during high tides, since the shore prevents the movement of the tidal wave and water accumulates here during the entire time between low tide and high tide.

The highest tide (about 18 m) is observed in one of the bays on the coast in Canada. In Russia, the highest tides (13 m) occur in the Gizhiginskaya and Penzhinskaya bays of the Sea of Okhotsk. In the inland seas (for example, in the Baltic or Black), the ebb and flow of the tides are almost imperceptible, because masses of water moving along with the ocean tidal wave do not have time to penetrate into such seas. But still, in every sea or even lake, independent tidal waves with a small mass of water arise. For example, the height of tides in the Black Sea reaches only 10 cm.

In the same area, the height of the tide varies, since the distance from the Moon to the Earth and highest height Moons above the horizon change over time, and this leads to changes in the magnitude of tidal forces.

Tides and Sun

The sun also affects the tides. But the tidal forces of the Sun are 2.2 times less than the tidal forces of the Moon.

During the new moon and full moon, the tidal forces of the Sun and Moon act in the same direction - then the highest tides are obtained. But during the first and third quarters of the Moon, the tidal forces of the Sun and Moon counteract, so the tides are smaller.

Tides in the air shell of the Earth and in its solid body

Tidal phenomena occur not only in water, but also in air envelope Earth. They are called atmospheric tides. Tides also occur in the solid body of the Earth, since the Earth is not absolutely solid. Vertical fluctuations of the Earth's surface due to tides reach several tens of centimeters.

Practical use of tides

A tidal power plant is a special type of hydroelectric power station that uses the energy of tides, and in fact kinetic energy rotation of the Earth. Tidal power plants are built on the shores of seas, where the gravitational forces of the Moon and the Sun change the water level twice a day. Fluctuations in water levels near the shore can reach 18 meters.

In 1967, a tidal power station was built in France at the mouth of the Rance River.

In Russia, since 1968, an experimental TPP has been operating in Kislaya Bay on the coast of the Barents Sea.

There are PES abroad - in France, Great Britain, Canada, China, India, the USA and other countries.

The ebb and flow of the tides is currently believed to be caused by the gravitational pull of the Moon. So, the Earth turns to the satellite in one direction or another, the Moon attracts this water to itself - these are the tides. In the area where the water leaves there are low tides. The earth rotates, ebbs and flows change each other. Like this lunar theory, in which everything is fine except for a number of unexplained facts.

For example, did you know that the Mediterranean Sea is considered tidal, but near Venice and on the Eurekos Strait in eastern Greece, the tides are up to one meter or more. This is considered one of the mysteries of nature. However, Italian physicists discovered in the east Mediterranean Sea, at a depth of more than three kilometers, a chain of underwater whirlpools, each ten kilometers in diameter. Interesting coincidence of abnormal tides and whirlpools, isn't it?

A pattern has been noticed: where there are whirlpools, in oceans, seas and lakes, there are ebbs and flows, and where there are no whirlpools, there are no ebbs and flows... The vastness of the world's oceans is completely covered with whirlpools, and whirlpools have the property of a gyroscope to maintain the position of the axis in space, regardless of the rotation of the earth.

If you look at the earth from the side of the Sun, the whirlpools, rotating with the Earth, overturn twice a day, as a result of which the axis of the whirlpools precesses (1-2 degrees) and creates a tidal wave, which is the cause of ebbs and flows, and vertical movement ocean waters.

Precession of a top

Giant ocean whirlpool

The Mediterranean Sea is considered tidal, but near Venice and on the Eurekos Strait in eastern Greece, the tides are up to one meter or more. And this is considered one of the mysteries of nature, but at the same time, Italian physicists discovered in the east of the Mediterranean Sea, at a depth of more than three kilometers, a chain of underwater whirlpools, each ten kilometers in diameter. From this we can conclude that along the coast of Venice, at a depth of several kilometers, there is a chain of underwater whirlpools.

If in the Black Sea the water rotated like in the White Sea, then the ebb and flow of the tides would be more significant. If a bay is flooded by a tidal wave and the wave swirls there, then the ebbs and flows in this case are higher... The place of whirlpools, and atmospheric cyclones and anticyclones in science, at the intersection of oceanology, meteorology, and celestial mechanics studying gyroscopes. The behavior of atmospheric cyclones and anticyclones, I believe, is similar to the behavior of whirlpools in the oceans.

To test this idea, I mounted a fan on the globe, where the whirlpool is located, and instead of blades I inserted metal balls on springs. I turned on the fan (whirlpool), simultaneously rotating the globe both around its axis and around the Sun, and got an imitation of the ebb and flow of the tides.

The attractiveness of this hypothesis is that it can be quite convincingly tested using a whirlpool fan attached to the globe. The sensitivity of the whirlpool gyroscope is so high that the globe has to be rotated extremely slowly (one revolution every 5 minutes). And if a whirlpool gyroscope is installed on a globe at the mouth of the Amazon River, then without a doubt, it will show the exact mechanics of the ebb and flow of the Amazon River. When only the globe rotates around its axis, the gyroscope-whirlpool tilts in one direction and stands motionless, and if the globe is moved in orbit, the whirlpool-horoscope begins to oscillate (precess) and gives two ebbs and flows per day.

Doubts about the presence of precession in whirlpools, as a result of slow rotation, are removed by the high speed of overturning of whirlpools, in 12 hours.. And we must not forget that the orbital speed of the earth is thirty times greater than the orbital speed of the moon.

The experience with the globe is more convincing than the theoretical description of the hypothesis. The drift of whirlpools is also associated with the effect of a gyroscope - a whirlpool, and depending on which hemisphere the whirlpool is located, and in which direction the whirlpool rotates around its axis, the direction of the whirlpool drift depends.

floppy disk

Tilting gyroscope

Experience with a gyroscope

Oceanographers in the middle of the ocean are not actually measuring the height of the tidal wave, but the wave created by the gyroscopic effect of the whirlpool created by precession, the axis of rotation of the whirlpool. And only whirlpools can explain the presence of a tidal hump on the opposite side of the earth. There is no fuss in nature, and if whirlpools exist, then they have a purpose in nature, and this purpose, I believe, is the vertical and horizontal mixing of ocean waters to equalize the temperature and oxygen content in the world's oceans.

And even if lunar tides existed, they would not mix ocean waters. Whirlpools, to some extent, prevent the oceans from silting up. If a couple of billion years ago, the earth actually rotated faster, then the whirlpools were more active. Mariana Trench and the Mariana Islands, I believe the result of the whirlpool.

The tide calendar existed long before the discovery of the tidal wave. Just as there was a regular calendar, before Ptolemy, and after Ptolemy, and before Copernicus, and after Copernicus. Today there are also unclear questions about the characteristics of the tides. Thus, in some places (the South China Sea, the Persian Gulf, the Gulf of Mexico and the Gulf of Thailand) there is only one tide per day. In a number of regions of the Earth (for example, in Indian Ocean) there are sometimes one or two hot tides per day.

500 years ago, when the idea of ebbs and flows was formed, thinkers did not have enough technical means to test this idea, and little was known about eddies in the oceans. And today, this idea, with its attractiveness and plausibility, is so rooted in the consciousness of the public and thinkers that it will not be easy to abandon it.

Why, every year and every decade, on the same calendar day (for example, the first of May) at the mouths of rivers and bays, there is not the same tidal wave? I believe the whirlpools that are located at the mouths of rivers and bays drift and change their size.

And if the cause of the tidal wave was the gravity of the moon, the height of the tides would not change for millennia. There is an opinion that a tidal wave moving from east to west is created by the gravity of the moon, and the wave floods bays and river mouths. But why, the mouth of the Amazon floods well, but the Bay of La Plata, which is located south of the Amazon, does not flood very well, although by all measures the Bay of La Plata should flood more than the Amazon.

I believe that a tidal wave at the mouth of the Amazon is created by one whirlpool, and for the La Plata neck of the river a tidal wave is created by another whirlpool, less powerful (diameter, height, revolutions).

Amazon Maelstrom

The tidal wave crashes into the Amazon at a speed of about 20 kilometers per hour, the height of the wave is about five meters, the width of the wave is ten kilometers. These parameters are more suitable for a tidal wave created by the precession of an eddy. And if it were a lunar tidal wave, it would hit at a speed of several hundred kilometers per hour, and the width of the wave would be about a thousand kilometers.

It is believed that if the depth of the ocean was 20 kilometers, then the lunar wave would move as expected at 1600 km.hour, they say that the shallow ocean interferes with it. And now it is crashing into the Amazon at a speed of 20 km.h., and into the Fuchunjiang River at a speed of 40 km.h. I think the math is dubious.

And if the Moon wave moves so slowly, then why in pictures and animations the tidal hump is always directed towards the Moon, the Moon rotates much faster. And it is not clear why, the water pressure does not change, under the tidal hump, at the bottom of the ocean... There are zones in the oceans where there are no ebbs and flows at all (amphidromic points).

Amphidromic point

M2 tide, tide height shown in color. White lines are cotidal lines with a phase interval of 30°. Amphidromic points are dark blue areas where white lines converge. Arrows around these points indicate the direction of the “run around”.An amphidromic point is a point in the ocean where the tidal wave amplitude is zero. The height of the tide increases with distance from the amphidromic point. Sometimes these points are called tide nodes: the tidal wave “runs around” this point clockwise or counterclockwise. The cotidal lines converge at these points. Amphidromic points arise due to the interference of the primary tidal wave and its reflections from the coastline and underwater obstacles. The Coriolis force also contributes.

Although for a tidal wave they are in a convenient zone, I believe in these zones the whirlpools rotate extremely slowly. It is believed that the maximum tides occur during the new moon, due to the fact that the Moon and the Sun exert gravity on the Earth in the same direction.

For reference: a gyroscope is a device that, due to rotation, reacts differently to external forces than a stationary object. The simplest gyroscope is a spinning top. By untwisting the spinning top on a horizontal surface and tilting the surface, you will notice that the spinning top maintains horizontal torsion.

But on the other hand, on a new moon the earth’s orbital speed is maximum, and on a full moon it is minimum, and the question arises which of the reasons is the key. The distance from the earth to the moon is 30 diameters of the earth, the approach and distance of the moon from the earth is 10 percent, this can be compared by holding a cobblestone and a pebble with outstretched arms, and bringing them closer and further away by 10 percent, are ebbs and flows possible with such mathematics. It is believed that at the new moon, the continents run into a tidal hump, at a speed of about 1600 kilometers per hour, is this possible?

It is believed that tidal forces have stopped the rotation of the moon, and now it rotates synchronously. But there are more than three hundred known satellites, and why did they all stop at the same time, and where did the force that rotated the satellites go... Gravitational force between the Sun and the Earth does not depend on the orbital speed of the Earth, and the centrifugal force depends on the orbital speed of the Earth, and this fact cannot be the cause of the lunar tides.

Calling ebbs and flows, the phenomenon of horizontal and vertical movement of ocean waters, is not entirely true, for the reason that most whirlpools are not in contact with coastline ocean... If you look at the Earth from the Sun, the whirlpools that are located on the midnight and noon side of the Earth are more active, since they are in the zone of relative motion.

And when the whirlpool enters the zone of sunset and dawn and becomes edge-on to the Sun, the whirlpool falls into the power of Coriolis forces and subsides. During the new moon, the tides increase and decrease due to the fact that the orbital speed of the earth is at its maximum...

Material sent by the author: Yusup Khizirov

British photographer Michael Marten created a series of original photographs capturing the British coastline from the same angles, but in different time. One shot at high tide and one at low tide.

It turned out quite unusual, but positive reviews about the project, literally forced the author to start publishing the book. The book, called "Sea Change", was published in August this year and was released in two languages. It took Michael Marten about eight years to create his impressive series of photographs. The time between high and low water averages just over six hours. Therefore, Michael has to linger in each place for longer than just the time of a few shutter clicks.

1. The author had been nurturing the idea of creating a series of such works for a long time. He was looking for how to realize changes in nature on film, without human influence. And I found it by chance, in one of the coastal Scottish villages, where I spent the whole day and caught the time of high and low tide.

3. Periodic oscillations water levels (rises and falls) in water areas on Earth are called ebbs and flows.

The highest water level observed in a day or half a day during high tide is called high water, the lowest level during low tide is called low water, and the moment of reaching these maximum level marks is called the standing (or stage) of high tide or low tide, respectively. Average level seas - conventional value, above which the level marks are located during high tides, and below which during low tides. This is the result of averaging large series of urgent observations.

Vertical fluctuations in water level during high and low tides are associated with horizontal movements of water masses in relation to the shore. These processes are complicated by wind surge, river flow and other factors. Horizontal movements of water masses in the coastal zone are called tidal (or tidal) currents, while vertical fluctuations in water levels are called ebbs and flows. All phenomena associated with ebbs and flows are characterized by periodicity. Tidal currents periodically change direction to the opposite direction, unlike ocean currents, moving continuously and unidirectionally, are caused by general circulation atmosphere and cover large areas of open ocean.

4. High and low tides alternate cyclically in accordance with changing astronomical, hydrological and meteorological conditions. The sequence of tidal phases is determined by two maxima and two minima in the daily cycle.

5. Although the Sun is playing significant role in tidal processes, decisive factor Their development is driven by the gravitational pull of the Moon. The degree of influence of tidal forces on each particle of water, regardless of its location on earth's surface, determined by law universal gravity Newton.
This law states that two material particles attract each other with a force directly proportional to the product of the masses of both particles and inversely proportional to the square of the distance between them. It is understood that the greater the mass of the bodies, the greater the force of mutual attraction that arises between them (with the same density, a smaller body will create less attraction than a larger one).

6. The law also means that the greater the distance between two bodies, the less attraction there is between them. Since this force is inversely proportional to the square of the distance between two bodies, the distance factor plays a much larger role in determining the magnitude of the tidal force than the masses of the bodies.

The gravitational attraction of the Earth, acting on the Moon and keeping it in near-Earth orbit, is opposite to the force of attraction of the Earth by the Moon, which tends to move the Earth towards the Moon and “lifts” all objects located on the Earth in the direction of the Moon.

The point on the earth's surface located directly below the Moon is only 6,400 km from the center of the Earth and on average 386,063 km from the center of the Moon. In addition, the mass of the Earth is 81.3 times the mass of the Moon. Thus, at this point on the earth’s surface, the Earth’s gravity acting on any object is approximately 300 thousand times greater than the Moon’s gravity.

7. It is a common idea that the water on Earth, directly below the Moon, rises in the direction of the Moon, which leads to the outflow of water from other places on the Earth's surface, however, since the attraction of the Moon is so small in comparison with the attraction of the Earth, it would not be enough to lift such a huge weight.
However, the oceans, seas and large lakes on Earth, being large liquid bodies, are free to move under the influence of lateral displacement forces, and any weak trend causes them to move horizontally. All waters that are not directly under the Moon are subject to the action of the component of the Moon's gravitational force directed tangentially (tangentially) to the earth's surface, as well as its component directed outward, and are subject to horizontal displacement relative to the solid earth's crust.

As a result, water flows from adjacent areas of the earth's surface towards a place located under the Moon. The resulting accumulation of water at a point under the Moon forms a tide there. The tidal wave itself in the open ocean has a height of only 30–60 cm, but it increases significantly when approaching the shores of continents or islands.
Due to the movement of water from neighboring areas towards a point under the Moon, corresponding ebbs of water occur at two other points located at a distance from it, equal to a quarter circumference of the Earth. It is interesting to note that the decrease in sea level at these two points is accompanied by a rise in sea level not only on the side of the Earth facing the Moon, but also on the opposite side.

8. This fact is also explained by Newton's law. Two or more objects located at different distances from the same source of gravity and, therefore, subjected to the acceleration of gravity of different magnitudes, move relative to each other, since the object closest to the center of gravity is most strongly attracted to it.

Water at the sublunar point experiences a stronger pull towards the Moon than the Earth below it, but the Earth in turn has a stronger pull towards the Moon than water on the opposite side of the planet. Thus, a tidal wave arises, which on the side of the Earth facing the Moon is called direct, and on the opposite side - reverse. The first of them is only 5% higher than the second.

9. Due to the rotation of the Moon in its orbit around the Earth, approximately 12 hours and 25 minutes pass between two successive high tides or two low tides in a given place. The interval between the climaxes of successive high and low tides is approx. 6 hours 12 minutes The period of 24 hours 50 minutes between two successive tides is called a tidal (or lunar) day.

10. Inequalities of tide values. Tidal processes are very complex and many factors must be taken into account to understand them. In any case, the main features will be determined:
1) the stage of development of the tide relative to the passage of the Moon;
2) tidal amplitude and
3) the type of tidal fluctuations, or the shape of the water level curve.
Numerous variations in the direction and magnitude of tidal forces give rise to differences in the magnitude of morning and evening tides in a given port, as well as between the same tides in different ports. These differences are called tide inequalities.

Semi-diurnal effect. Usually within a day, due to the main tidal force - the rotation of the Earth around its axis - two complete tidal cycles are formed.

11. Seen from the outside North Pole ecliptic, it is obvious that the Moon rotates around the Earth in the same direction in which the Earth rotates around its axis - counterclockwise. At each next revolution given point the earth's surface again takes a position directly under the Moon somewhat later than during the previous revolution. For this reason, both the ebb and flow of the tides are delayed by approximately 50 minutes every day. This value is called lunar delay.

12. Semi-monthly inequality. This main type of variation is characterized by a periodicity of approximately 143/4 days, which is associated with the rotation of the Moon around the Earth and its passage through successive phases, in particular syzygies (new moons and full moons), i.e. moments when the Sun, Earth and Moon are located on the same straight line.

So far we have touched only on the tidal influence of the Moon. The gravitational field of the Sun also affects the tides, however, although the mass of the Sun is much greater than the mass of the Moon, the distance from the Earth to the Sun is so greater than the distance to the Moon that the tidal force of the Sun is less than half that of the Moon.

13. However, when the Sun and Moon are on the same straight line, either on the same side of the Earth or on opposite sides (during the new moon or full moon), their gravitational forces add up, acting along the same axis, and the solar tide overlaps the lunar tide.

14. Likewise, the attraction of the Sun increases the ebb caused by the influence of the Moon. As a result, the tides become higher and the tides lower than if they were caused only by the Moon's gravity. Such tides are called spring tides.

15. When the gravitational force vectors of the Sun and the Moon are mutually perpendicular (during quadratures, i.e. when the Moon is in the first or last quarter), their tidal forces oppose, since the tide caused by the attraction of the Sun is superimposed on the ebb caused by the Moon.

16. Under such conditions, the tides are not as high and the tides are not as low as if they were caused only by the gravitational force of the Moon. Such intermediate ebbs and flows are called quadrature.

17. The range of high and low water marks in this case is reduced by approximately three times compared to the spring tide.

18. Lunar parallactic inequality. The period of fluctuations in tidal heights, which occurs due to lunar parallax, is 271/2 days. The reason for this inequality is the change in the distance of the Moon from the Earth during the latter’s rotation. Due to the elliptical shape lunar orbit The tidal force of the Moon at perigee is 40% higher than at apogee.

Daily inequality. The period of this inequality is 24 hours 50 minutes. The reasons for its occurrence are the rotation of the Earth around its axis and a change in the declination of the Moon. When the Moon is near the celestial equator, the two high tides on a given day (as well as the two low tides) differ slightly, and the heights of morning and evening high and low waters are very close. However, as the Moon's north or south declination increases, morning and evening tides of the same type differ in height, and when the Moon reaches its greatest north or south declination, this difference is greatest.

19. Tropical tides are also known, so called because the Moon is almost above the Northern or Southern tropics.

Diurnal inequality does not significantly affect the heights of two successive low tides in Atlantic Ocean, and even its effect on tidal heights is small compared to the overall amplitude of the fluctuations. However, in Pacific Ocean diurnal unevenness is three times greater in low tide levels than in high tide levels.

Semiannual inequality. Its cause is the revolution of the Earth around the Sun and the corresponding change in the declination of the Sun. Twice a year for several days during the equinoxes, the Sun is near the celestial equator, i.e. its declination is close to 0. The Moon is also located near the celestial equator for approximately one day every half month. Thus, during the equinoxes, there are periods when the declinations of both the Sun and the Moon are approximately equal to 0. The total tidal effect of the attraction of these two bodies at such moments is most noticeably manifested in areas located close to earth's equator. If at the same time the Moon is in the new moon or full moon phase, the so-called. equinoctial spring tides.

20. Solar parallactic inequality. The period of manifestation of this inequality is one year. Its cause is the change in the distance from the Earth to the Sun in the process orbital movement Earth. Once for each revolution around the Earth, the Moon is at its shortest distance from it at perigee. Once a year, around January 2, the Earth, moving in its orbit, also reaches the point of closest approach to the Sun (perihelion). When these two moments of closest approach coincide, causing the greatest total tidal force, we can expect more high levels tides and more low levels low tides Likewise, if the passage of aphelion coincides with apogee, lower tides and shallower tides occur.

21. Greatest tidal amplitudes. The world's highest tide is generated by strong currents in Minas Bay in the Bay of Fundy. Tidal fluctuations here are characterized by a normal course with a semi-diurnal period. The water level at high tide often rises by more than 12 m in six hours, and then drops by the same amount over the next six hours. When the effect of spring tide, the position of the Moon at perigee and the maximum declination of the Moon occur on the same day, the tide level can reach 15 m. This exceptionally large amplitude of tidal fluctuations is partly due to the funnel-shaped shape of the Bay of Fundy, where the depths decrease and the shores move closer together towards top of the bay. Causes of tides, which were the subject constant study for many centuries, are among those problems that have given rise to many controversial theories even in relatively recent times

22. Charles Darwin wrote in 1911: “There is no need to look ancient literature for the sake of grotesque theories of the tides.” However, sailors manage to measure their height and take advantage of the tides without having any idea of the actual causes of their occurrence.

I think that we don’t have to worry too much about the causes of the tides. Based on long-term observations, special tables are calculated for any point in the earth’s waters, which indicate the times of high and low water for each day. I’m planning my trip, for example, to Egypt, which is famous for its shallow lagoons, but try to plan in advance so that the full water occurs in the first half of the day, which will allow most daylight hours to fully ride.
Another question related to tides that is interesting for kiters is the relationship between wind and water level fluctuations.

23. Folk sign claims that at high tide the wind intensifies, but at low tide it turns sour.
The influence of wind on tidal phenomena is more understandable. The wind from the sea pushes the water towards the coast, the height of the tide increases above normal, and at low tide the water level also exceeds the average. On the contrary, when the wind blows from land, water is driven away from the coast, and sea level drops.

24. The second mechanism operates by increasing atmospheric pressure over a vast area of water, causing the water level to decrease as the superimposed weight of the atmosphere is added. When atmospheric pressure increases by 25 mmHg. Art., the water level drops by approximately 33 cm. Zone high pressure or anticyclone is usually called good weather, but not for kiters. There is calm in the center of the anticyclone. A decrease in atmospheric pressure causes a corresponding increase in water levels. Consequently, a sharp drop in atmospheric pressure combined with hurricane-force winds can cause a noticeable rise in water levels. Such waves, although called tidal, are in fact not associated with the influence of tidal forces and do not have the periodicity characteristic of tidal phenomena.

But it is quite possible that low tides can also influence the wind, for example, a decrease in the water level in coastal lagoons leads to greater warming of the water, and as a result to a decrease in the temperature difference between the cold sea and the heated land, which weakens the breeze effect.