British photographer Michael Martin (Michael Marten) created a series of original shots that capture the coast of Britain in the same angle, but at different times. One shot at high tide and one at low tide.
It turned out very unusual, and the positive feedback about the project literally forced the author to start releasing 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 shots. The time between high and low water averages a little over six hours. Therefore, Michael has to linger in each place longer than just a few clicks of the shutter.
1. The idea of creating a series of such works was nurtured by the author for a long time. He was looking for how to realize the changes of nature on film, without human influence. And I found it by chance, in one of the seaside Scottish villages, where I spent the whole day and found the time of high and low tide.
3. Periodic fluctuations in the water level (ups and downs) in the waters on Earth are called high and low tides.
The highest water level observed in a day or half a day at high tide is called high tide, the lowest level at low tide is called low tide, and the moment these limit marks are reached is called standing (or stage), respectively, high tide or low tide. Middle level seas - a conditional value, above which the level marks are located during high tides, and below - during low tides. This is the result of averaging large series of urgent observations.
Vertical fluctuations in the water level during high and low tides are associated with horizontal movements water masses in relation to the coast. These processes are complicated by wind surge, river runoff and other factors. Horizontal movements of water masses in the coastal zone are called tidal (or tidal) currents, while vertical fluctuations in the water level are called ebbs and flows. All phenomena associated with ebbs and flows are characterized by periodicity. Tidal currents periodically reverse direction, in contrast to them, ocean currents, moving continuously and unidirectionally, are due to general circulation atmosphere and cover large expanses of the open ocean.
4. High and low tides alternate cyclically in accordance with the changing astronomical, hydrological and meteorological conditions. The sequence of tidal phases is determined by two maxima and two minima in the daily course.
5. Although the Sun plays an essential role in tidal processes, the decisive factor in their development is the force of the gravitational attraction of the Moon. The degree of influence of tidal forces on each particle of water, regardless of its location on the earth's surface, is determined by the law gravity Newton.
This law states that two material particles are attracted to each other with a force that is directly proportional to the product of the masses of both particles and inversely proportional to the square of the distance between them. This implies that the greater the mass of bodies, the greater the force of mutual attraction 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 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 on the Earth in the direction of the Moon.
The point on the earth's surface, located directly under the Moon, is only 6,400 km away 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 attraction of the Earth, acting on any object, is approximately 300 thousand times greater than the attraction of the Moon.
7. It is a common notion that the water on Earth, directly under the Moon, rises in the direction of the Moon, causing water to flow away from other places on the Earth's surface, however, since the Moon's pull is so small compared to the Earth's, it would not be enough to lift such a huge weight.
However, the oceans, seas, and large lakes on Earth, being large fluid bodies, are free to move under the force of lateral displacement, and any slight horizontal shear tendency sets them in motion. 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 surface. earth's crust.
As a result, there is a flow of water from the adjacent regions of the earth's surface towards a place under the moon. The resulting accumulation of water at a point under the Moon forms a tide there. The actual tidal wave 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 regions towards a point under the Moon, corresponding outflows of water occur at two other points remote from it at a distance equal to a quarter of the circumference of the Earth. It is interesting to note that the lowering of the ocean 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 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 a sublunar point experiences a stronger attraction to the Moon than the Earth below it, but the Earth, in turn, is more strongly attracted to 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 it is called 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 h 12 min. The period of 24 hours and 50 minutes between two successive high tides is called a tidal (or lunar) day.
10. Inequalities of tide values. Tidal processes are very complex, so many factors must be taken into account in order to understand them. In any case, the main features will be determined by:
1) the stage of tide development relative to the passage of the Moon;
2) the amplitude of the tide 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 magnitudes 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-permanent effect. Usually during the 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 side North Pole of the ecliptic, it is obvious that the Moon revolves around the Earth in the same direction in which the Earth revolves around its axis - counterclockwise. With each next turn given point the earth's surface again takes a position directly under the moon a little later than during the previous revolution. For this reason, both high and low tides are late every day by about 50 minutes. This value is called the 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 the passage of successive phases, in particular syzygies (new moons and full moons), i.e. moments when the sun, earth and moon are in a straight line.
So far, we have dealt only with the tidal action of the Moon. The Sun's gravitational field also acts on the tides, but although the Sun's mass is much larger than the Moon's, the distance from the Earth to the Sun is so much greater than the distance to the Moon that the Sun's tidal force is less than half that of the Moon.
13. However, when the Sun and the Moon are on the same straight line, both on the same side of the Earth, and on different ones (on a new moon or a full moon), their attractive forces add up, acting along one axis, and the solar tide is superimposed on the lunar tide.
14. Similarly, the attraction of the Sun increases the ebb caused by the influence of the Moon. As a result, the tides are higher and the tides are lower than if they were caused only by the pull of the moon. Such tides are called spring tides.
15. When the vectors of the attraction 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 counteract, 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 so high, and the tides are not so low, as if they were due only to the gravitational force of the Moon. Such intermediate tides 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 parallax inequality. The period of fluctuations in the heights of the tides, 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 rotation of the latter. Due to the elliptical shape of the lunar orbit, the Moon's tidal force is 40% higher at perigee 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 the 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 two low tides) differ little, and the heights of the 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 over 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 the heights of the tides is small compared to the total amplitude of the oscillations. However, in pacific ocean daily unevenness is manifested in the levels of low tides three times stronger than in the levels of tides.
Semi-annual 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 approximately during the day every fortnight. 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 noticeable in areas located near the earth's equator. If at the same time the Moon is in the phase of a new moon or a full moon, so-called. equinoctial spring tides.
20. Solar parallax inequality. The period of manifestation of this inequality is one year. Its cause is a change in the distance from the Earth to the Sun in the process of the Earth's orbital motion. Once for each revolution around the Earth, the Moon is at the 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 net tidal force, higher tide levels and lower tidal levels can be expected. Similarly, if the passage of aphelion coincides with the apogee, less high tides and shallower low tides occur.
21. The greatest amplitudes of the tides. The world's highest tide is formed by strong currents in Minas Bay in the Bay of Fundy. Tidal fluctuations here are characterized by a normal course with a semidiurnal 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 action of the spring tide, the position of the Moon at perigee, and the maximum declination of the Moon occur in one day, the tide level can reach 15 m. the top of the bay. The causes of tides, which have been the subject of constant study for many centuries, are among the problems that have given rise to many conflicting theories even in relatively recent times.
22. C. Darwin wrote in 1911: "There is no need to search for ancient literature for the sake of grotesque theories of tides." However, sailors manage to measure their height and use the possibilities of tides without having an idea of the real causes of their occurrence.
I think that we can especially not bother about the causes of the origin of the tides. Based on long-term observations, special tables are calculated for any point in the water area of the earth, which indicate the time of high and low water for each day. I am planning my trip, for example, to Egypt, which is just famous for its shallow lagoons, but try to guess in advance so that full water falls in the first half of the day, which will allow you to fully ride most of the daylight hours.
Another issue related to tides of interest to the kiter is the relationship between wind and water level fluctuations.
23. A folk sign claims that the wind increases at high tide and, on the contrary, turns sour at low tide.
The influence of wind on tidal phenomena is more clearly understood. The wind from the sea drives the water towards the shore, the height of the tide rises above normal, and at low tide the water level also exceeds the average. On the contrary, when the wind blows from the land, the water is driven away from the coast, and the sea level drops.
24. The second mechanism operates by increasing atmospheric pressure over a vast area of water, lowering the water level, as the superimposed weight of the atmosphere is added. When atmospheric pressure increases by 25 mm Hg. Art., the water level drops by about 33 cm. A high pressure zone or anticyclone is usually called good weather, but not for a kiter. Calm in the center of the anticyclone. A decrease in atmospheric pressure causes a corresponding rise in the water level. Therefore, a sharp drop in atmospheric pressure, combined with hurricane-force winds, can cause a noticeable rise in the water level. Such waves, although they are called tidal waves, 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 affect 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.
Ebb and flow
high tide and low tide- periodic vertical fluctuations in the level of the ocean or sea, which are the result of changes in the positions of the Moon and the Sun relative to the Earth, coupled with the effects of the Earth's rotation and the features of this relief, and manifested in a periodic horizontal displacement of water masses. Tides cause changes in sea level and periodic currents, known as tidal currents, making tide prediction important for coastal navigation.
The intensity of these phenomena depends on many factors, but the most important of them is the degree of connection of water bodies with the oceans. The more closed the reservoir, the less the degree of manifestation of tidal phenomena.
The yearly recurring tidal cycle remains unchanged due to the exact compensation of the forces of attraction between the Sun and the center of mass of the planetary pair and the forces of inertia applied to this center.
Since the position of the Moon and the Sun in relation to the Earth periodically changes, the intensity of the resulting tidal phenomena also changes.
Low tide at Saint Malo
Story
Ebb tides played a significant role in supplying the coastal population with seafood, allowing them to collect on the exposed seabed food suitable for eating.
Terminology
Low water (Brittany, France)
The maximum level of the water surface at high tide is called full water, and the minimum at low tide - low water. In the ocean, where the bottom is even, and the land is far away, high water manifests itself as two “bulges” of the water surface: one of them is from the side of the moon, and the other is at the opposite end the globe. There may also be two more smaller swellings on the side directed towards the Sun and opposite to it. An explanation of this effect can be found below, in the section tide physics.
Since the Moon and the Sun move relative to the Earth, water humps move with them, forming tidal waves and tidal currents. In the open sea, tidal currents are rotational in nature, and near the coast and in narrow bays and straits, they are reciprocating.
If the whole Earth were covered with water, we would observe two regular high and low tides daily. But since the unimpeded propagation of tidal waves is prevented by land areas: islands and continents, and also due to the action of the Coriolis force on moving water, instead of two tidal waves, there are many small waves that slowly (in most cases with a period of 12 h 25.2 min ) run around a point called amphidromic, where the tide amplitude is zero. The dominant component of the tide (the lunar tide M2) forms about a dozen amphidromic points on the surface of the World Ocean with wave motion clockwise and about the same counterclockwise (see map). All this makes it impossible to predict the time of the tide only on the basis of the positions of the Moon and the Sun relative to the Earth. Instead, they use the "yearbook of tides" - a reference tool for calculating the time of the onset of tides and their height at various points on the globe. Tide tables are also used, with data on the moments and heights of low and high waters, calculated a year ahead for major tidal ports.
Tide component M2
If we connect points on the map with the same tide phases, we get the so-called cotidal lines radiating from the amphidromic point. Typically, cotidal lines characterize the position of the crest of the tidal wave for each hour. In fact, the cotidal lines reflect the speed of propagation of the tidal wave in 1 hour. Maps that show lines of equal amplitudes and phases of tidal waves are called cotidal cards.
high tide- difference between highest level water at high tide (high tide) and its lowest level at low tide (low tide). The height of the tide is a variable value, however, its average indicator is given when characterizing each section of the coast.
Depending on the relative position of the Moon and the Sun, small and large tidal waves can reinforce each other. For such tides, special names have historically developed:
- Quadrature tide- the smallest tide, when the tide-forming forces of the Moon and the Sun act at right angles to each other (this position of the luminaries is called quadrature).
- spring tide- the greatest tide, when the tide-forming forces of the Moon and the Sun act along the same direction (this position of the luminaries is called syzygy).
The smaller or larger the tide, the smaller or, respectively, the greater the ebb.
The highest tides in the world
It can be observed in the Bay of Fundy (15.6-18 m), which is located on the east coast of Canada between New Brunswick and Nova Scotia.
On the European continent, the highest tides (up to 13.5 m) are observed in Brittany near the city of Saint Malo. Here the tidal wave is focused by the coastline of the Cornwall (England) and Cotentin (France) peninsulas.
Tide physics
Modern wording
In relation to the planet Earth, the cause of tides is the presence of the planet in the gravitational field created by the Sun and the Moon. Since the effects they create are independent, the impact of these celestial bodies to Earth can be considered separately. In this case, for each pair of bodies, we can assume that each of them revolves around a common center of gravity. For the Earth-Sun pair, this center is located in the depths of the Sun at a distance of 451 km from its center. For the Earth-Moon pair, it is located deep in the Earth at a distance of 2/3 of its radius.
Each of these bodies experiences the action of tidal forces, the source of which is the gravitational force and internal forces that ensure the integrity of the celestial body, in the role of which is the force of its own attraction, hereinafter referred to as self-gravity. The emergence of tidal forces is most clearly seen in the example of the Earth-Sun system.
The tidal force is the result of the competing interaction of the gravitational force directed towards the center of gravity and decreasing inversely with the square of the distance from it, and the fictitious centrifugal force of inertia due to the rotation of a celestial body around this center. These forces, being opposite in direction, coincide in magnitude only at the center of mass of each of the celestial bodies. Through action internal forces The Earth revolves around the center of the Sun as a whole with a constant angular velocity for each element of its constituent mass. Therefore, as this element of mass moves away from the center of gravity, the centrifugal force acting on it grows in proportion to the square of the distance. A more detailed distribution of tidal forces in their projection onto a plane, perpendicular to the plane ecliptic are shown in Fig.1.
Fig.1 Scheme of the distribution of tidal forces in the projection onto a plane perpendicular to the Ecliptic. A gravitating body is either on the right or on the left.
According to the Newtonian paradigm, the reproduction of changes in the shape of the bodies subjected to their action, achieved as a result of the action of tidal forces, can be achieved only if these forces are fully compensated by other forces, which may include the force of universal gravitation.
Fig.2 Deformation of the Earth's water shell as a result of the balance of tidal force, self-gravity force and the force of water reaction to the compressive force
As a result of the addition of these forces, tidal forces arise symmetrically on both sides of the globe, directed in different directions from it. The tidal force directed towards the Sun is of a gravitational nature, while that directed away from the Sun is a consequence of a fictitious inertial force.
These forces are extremely weak and cannot be compared with the forces of self-gravity (the acceleration they create is 10 million times less than the acceleration free fall). However, they cause a shift in the particles of water in the oceans (resistance to shear in water at low speeds is practically zero, while compression is extremely high), until the tangent to the surface of the water becomes perpendicular to the resulting force.
As a result, a wave arises on the surface of the oceans, occupying a constant position in systems of mutually gravitating bodies, but running along the surface of the ocean together with the daily movement of its bottom and coasts. Thus (in disregard ocean currents) each particle of water makes twice during the day oscillating motion up down.
The horizontal movement of water is observed only near the coast as a result of the rise in its level. The speed of movement is greater, the more gently the seabed is located.
Tidal potential
(the concept of acad. Shuleikin)
Neglecting the size, structure and shape of the Moon, we write down the specific force of attraction of a test body located on the Earth. Let be the radius vector directed from the test body towards the Moon, be the length of this vector. In this case, the force of attraction of this body by the Moon will be equal to
where is the selenometric gravitational constant. We place the test body at the point . The force of attraction of a test body placed at the center of mass of the Earth will be equal to
Here, and are understood as the radius vector connecting the centers of mass of the Earth and the Moon, and their absolute values. We will call the tidal force the difference between these two gravitational forces
In formulas (1) and (2), the Moon is considered to be a ball with a spherically symmetric mass distribution. The force function of attraction of the test body by the Moon does not differ in any way from the force function of attraction of the ball and is equal to The second force is applied to the center of mass of the Earth and is strictly constant value. To obtain the force function for this force, we introduce a time coordinate system. We draw the axis from the center of the Earth and direct it towards the Moon. We leave the directions of the other two axes arbitrary. Then the force function of the force will be equal to . Tidal potential will be equal to the difference of these two force functions. Let's designate it , we will get the Constant we will determine from the normalization condition, according to which the tide-forming potential in the center of the Earth zero. At the center of the Earth , It follows that . Therefore, we obtain the final formula for the tidal potential in the form (4)
Insofar as
For small values of , , the last expression can be represented in the following form
Substituting (5) into (4), we obtain
Deformation of the surface of the planet under the influence of ebbs and flows
The perturbing effect of the tidal potential deforms the level surface of the planet. Let us evaluate this effect, assuming that the Earth is a sphere with a spherically symmetric mass distribution. The unperturbed gravitational potential of the Earth on the surface will be equal to . For a dot. , located at a distance from the center of the sphere, the gravitational potential of the Earth is . Reducing by the gravitational constant, we get . Here the variables are and . Let us denote the ratio of the masses of the gravitating body to the mass of the planet by a Greek letter and solve the resulting expression for :
Since with the same degree of accuracy we get
Given the smallness of the ratio, the last expressions can be written as
Thus, we have obtained the equation of a biaxial ellipsoid, in which the axis of rotation coincides with the axis, i.e. with a straight line connecting the gravitating body with the center of the Earth. The semiaxes of this ellipsoid are obviously equal
At the end we give a small numerical illustration of this effect. Let's calculate the tidal "hump" on the Earth, caused by the attraction of the Moon. The radius of the Earth is km, the distance between the centers of the Earth and the Moon, taking into account the instability of the lunar orbit, is km, the ratio of the mass of the Earth to the mass of the Moon is 81:1. Obviously, when substituting into the formula, we get a value approximately equal to 36 cm.
see also
Notes
Literature
- Frish S. A. and Timoreva A. V. Course of General Physics, Textbook for the Physics and Mathematics and Physics and Technology Departments of State Universities, Volume I. M .: GITTL, 1957
- Shchuleykin V.V. Physics of the sea. M.: Publishing House "Nauka", Department of Earth Sciences of the Academy of Sciences of the USSR 1967
- Voight S.S. What are tides. Editorial Board of Popular Science Literature of the Academy of Sciences of the USSR
Links
- WXTide32 is a free tide charting program.
The level of the water surface in the seas and oceans of our planet periodically changes, fluctuates in certain intervals. These periodic oscillations are sea tides and ebbs.
The pattern of sea tides
To visualize tide pattern, imagine that you are standing on a sloping ocean coast, in some bay, 200-300 meters from the water. There are many different objects on the sand - an old anchor, a little closer a large pile of white stone. The iron hull of a small ship, which has fallen on its side, lies quite close by. The bottom of his hull in the bow is heavily torn. Obviously, once this ship, being close to the coast, ran into anchor. This accident occurred, in all likelihood, at low tide, and, apparently, the ship has been lying in this place for more than one year, since almost its entire hull has managed to become covered with brown rust. You are inclined to consider the careless captain to be the culprit of the ship's accident. Apparently, the anchor was the sharp tool that the ship that fell on its side ran into. You are looking for this anchor and cannot find it. Where could he go? Then you notice that the water is already approaching a pile of white stones, and then you guess that the anchor you saw has long been flooded by a tidal wave. Water "steps" on the shore, it continues to rise further and further up. Now a bunch of white stones turned out to be almost all hidden under water.The phenomena of sea tides
The phenomena of sea tides people have long associated with the movement of the moon, but this connection remained a mystery until the brilliant mathematician Isaac Newton did not explain on the basis of the law of gravitation discovered by him. The reason for these phenomena is the effect of the attraction of the Moon, exerted on the water shell of the Earth. Still famous Galileo Galilei connected the ebb and flow with the rotation of the Earth and saw in this one of the most reasonable and true evidence of the validity of the teachings of Nicolaus Copernicus, (more:). The Paris Academy of Sciences in 1738 announced a prize to the one who would give the most reasonable exposition of the theory of tides. Then received the award Euler, Maclaurin, D. Bernoulli and Cavalieri. The first three took Newton's law of gravity as the basis of their work, and the Jesuit Cavalieri explained the tides on the basis of Descartes' vortex hypothesis. However, the most outstanding work in this area belongs to Newton and Laplace, and all subsequent research is based on the findings of these great scientists.How to explain the phenomenon of ebb and flow
As the most obvious explain the phenomenon of ebb and flow. If, for simplicity, we assume that the earth's surface is entirely covered with a water shell, and look at the globe from one of its poles, then the picture of sea tides can be represented as follows.moon attraction
That part of the surface of our planet, which faces the moon, is closest to it; as a result, it is subjected to more force lunar attraction than, for example, the central part of our planet and, therefore, is pulled towards the Moon more than the rest of the Earth. Because of this, on the side facing the moon, a tidal hump is formed. At the same time, on the opposite side of the Earth, the least subjected to the attraction of the Moon, the same tidal hump appears. The earth therefore takes the form of a figure somewhat elongated along the straight line connecting the centers of our planet and the moon. Thus, on two opposite sides of the Earth, located on the same straight line, which passes through the centers of the Earth and the Moon, two large humps are formed, two huge water bulges. At the same time, on the other two sides of our planet, located at an angle of ninety degrees from the points of maximum tide indicated above, the greatest ebb occurs. Here the water falls more than anywhere else on the surface of the globe. The line connecting these points at the time of low tide is somewhat reduced, and thus the impression is created of an increase in the elongation of the Earth in the direction of the maximum points of the tide. These points of maximum tide, due to lunar attraction, constantly maintain their position relative to the Moon, but since the Earth rotates around its axis, during the day they seem to move over the entire surface of the globe. So in each area during the day there are two high and two low tides.Solar ebb and flow
The sun, like the moon, produces ebbs and flows by the force of its attraction. But it is located at a much greater distance from our planet compared to the Moon, and the solar tides that occur on Earth are almost two and a half times less than the lunar ones. So solar tides, are not observed separately, and only their influence on the magnitude of lunar tides is considered. For example, The highest sea tides occur during full moons and new moons., since at this time the Earth, the Moon and the Sun are on the same straight line, and our daylight increases the attraction of the Moon with its attraction. On the contrary, when we observe the Moon in the first or last quarter (phase), there are the smallest sea tides. This is explained by the fact that in this case lunar tide coincides with solar tide. The effect of the lunar attraction is reduced by the magnitude of the attraction of the Sun.Tidal friction
« Tidal friction", existing in our planet, in turn affects the lunar orbit, since the tidal wave caused by the lunar attraction has a reverse effect on the Moon, creating a tendency to accelerate its movement. As a result, the Moon gradually moves away from the Earth, its period of revolution increases, and it, in all probability, lags a little behind in its movement.The magnitude of the sea tides
In addition to the relative position in space of the Sun, Earth and Moon, on sea tides in each individual locality, the shape of the seabed and the nature of the contours of the coasts influence. It is also known that in closed seas, such as, for example, in the Aral, Caspian, Azov and Black, ebbs and flows are almost not observed. With difficulty, they can be found in the open oceans; here the tides barely reach one meter, the water level rises very slightly. But on the other hand, in some bays there are tides of such colossal magnitude that water rises to a height of more than ten meters and in some places floods colossal spaces.
Ebb and flow in the air and solid shells of the Earth
Ebb and flow also occur in the air and solid shells of the Earth. We hardly notice these phenomena in the lower layers of the atmosphere. For comparison, we point out that tides are not observed at the bottom of the oceans either. This circumstance is explained by the fact that the upper layers of the water shell are mainly involved in tidal processes. Ebb and flow in the air shell can be detected only with a very long observation of changes in atmospheric pressure. As for the earth's crust, each part of it, due to the tidal and ebb action of the moon, rises twice during the day and falls twice by about a few decimeters. In other words, the fluctuations of the solid shell of our planet are approximately three times smaller in magnitude than the fluctuations in the level of the surface of the oceans. Thus, our planet is breathing all the time, taking deep breaths and exhalations, and its outer shell, like the chest of a great miracle hero, it rises a little, then falls. These processes occurring in the solid shell of the Earth can only be detected with the help of instruments used to register earthquakes. It should be noted that ebbs and flows occur on other world bodies and have a huge impact on their development. If the Moon were stationary with respect to the Earth, then in the absence of other factors affecting the delays of the tidal wave, in any place on the globe every 6 hours there would be two high and two low tides per day. But since the Moon continuously revolves around the Earth and, moreover, in the same direction in which our planet also rotates around its axis, a certain delay is obtained: the Earth manages to turn to the Moon with each of its parts not during the day, but approximately in 24 hours and 50 minutes. Therefore, in each locality, the tide does not last exactly 6 hours, but about 6 hours and 12.5 minutes.Ebb and flow alternating
Moreover, it should be noted that the correct ebbs and flows is violated depending on the nature of the location of the continents on our planet and the continuous friction of water on the surface of the Earth. These irregularities in alternation sometimes reach several hours. Thus, the most "high" water does not occur at the moment of the culmination of the Moon, as follows from the theory, but several hours later than the passage of the Moon through the meridian; this delay is called the application hour of the port and sometimes reaches 12 hours. It used to be widely believed that the tides of the sea are associated with sea currents. Now everyone knows that these are phenomena of a different order. A tide is a kind of wave motion, similar to that which occurs due to wind. A floating object, when a tidal wave comes on, oscillates, as with a wave arising from the wind - forward and backward, down and up, but is not carried away by it like a current. The period of the tidal wave is about 12 hours and 25 minutes, and after this period of time the object usually returns to its original position. Force, flushing, many times less than the force of attraction. While the force of attraction is inversely proportional to the square of the distance between the attracting bodies, the force that causes tides is approximately is inversely proportional to the cube of this distance, rather than square it.Ebb and flow, as it is believed today, are caused by the attraction of the moon. So, the Earth turns to the satellite one way or another, the Moon attracts this water to itself - that's the tides. In the area where the water leaves - low tides. The earth rotates, ebbs and flows follow each other. Here is such 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 Evrykos Strait in eastern Greece, the tides are up to one meter or more. It 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, ten kilometers in diameter each. An interesting coincidence of anomalous tides and whirlpools, isn't it?
A regularity has been noticed, where there are whirlpools, in the oceans, seas and lakes, there are ebbs and flows, and where there are no whirlpools, there are no tides ... space, regardless of the rotation of the earth.
If you look at the earth from the side of the Sun, 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 the tides, and the vertical movement of ocean waters .
Top precession
Giant ocean whirlpool
The Mediterranean Sea is considered tidal, but near Venice and on the Evrykos 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, ten kilometers in diameter each. 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 as in the White Sea, then the ebbs and flows would be more significant. If the bay is flooded by a tidal wave and the wave twists there, then the tides in this case are higher ... The place of whirlpools, and atmospheric cyclones and anticyclones in science, at the junction 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, on the globe, where the whirlpool is located, I fixed the fan, instead of the blades, I inserted metal balls on springs. I turned on the fan (whirlpool) simultaneously rotating the globe both around the axis and around the Sun, and got an imitation of the ebb and flow.
The attractiveness of this hypothesis is that it is quite convincingly tested by 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 in 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 still, and if the globe is moved in orbit, the whirlpool-horoscope begins to oscillate (precess) and gives two high and low tides per day.
Doubts about the presence of precession in whirlpools, as a result of slow rotation, are removed by the high speed of overturning whirlpools, in 12 hours .. And do 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 the gyroscope-whirlpool, and depending on which hemisphere the whirlpool is located in, and in which direction the whirlpool rotates around its axis, the direction of whirlpool drift depends.
floppy disk
Tipping gyroscope
Experience with a gyroscope
Oceanologists 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 whirlpool's axis of rotation. 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 lunar tides, if they existed, would not mix the ocean waters. Whirlpools, to some extent, keep the oceans from silting up. If a couple of billion years ago, the earth really 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. As existed, and the usual calendar, before Ptolemy, and after Ptolemy, and before Copernicus, and after Copernicus. Today there are incomprehensible questions about the characteristics of the tides. So, in some places (the South China Sea, the Persian Gulf, the Gulf of Mexico and the Gulf of Thailand) there is only one high tide per day. In a number of regions of the Earth (for example, in the Indian Ocean), there is either one or two high tides a day.
500 years ago, when the idea of ebb and flow was being formed, thinkers did not have enough technical means to test this idea, and little was known about the whirlpools in the oceans. And today, this idea, with its attractiveness and plausibility, is so ingrained in the minds 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) in the mouths of rivers and bays, there is no identical tidal wave? I believe the whirlpools that are in 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 thousands of years. There is an opinion that a tidal wave moving from east to west is created by the attraction of the moon, and the wave floods the bays and estuaries. But why, the mouth of the Amazon floods well, and La Plata Bay, which is located south of the Amazon, does not flood very well, although La Plata Bay should flood more than the Amazon in all respects.
I suppose a tidal wave at the mouth of the Amazon is created by one whirlpool, and for the neck of La Plata a tidal wave is created by another whirlpool, less powerful (diameter, height, revolutions).
Maelstrom of the Amazon
A tidal wave crashes into the Amazon at a speed of about 20 kilometers per hour, the wave height is about five meters, the wave width is ten kilometers. These settings are more suitable for the tidal wave created by the precession of a whirlpool. And if it were a lunar tidal wave, then it would crash 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 it should be 1600 km / h, they say that the shallow ocean interferes with it. And now it crashes into the Amazon at a speed of 20 km/h, and into the Fuchunjiang River at a speed of 40 km/h. I guess the math is questionable.
And if the Moon wave moves so slowly, then why in the 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 show the direction of "running around".An amphidromic point is a point in the ocean where the amplitude of the tidal wave is zero. The height of the tide increases with distance from the amphidromic point. Sometimes these points are called tidal 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 in the new moon, for the reason 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 the top. By spinning the top on a horizontal surface and tilting the surface, you will notice that the top retains horizontal torsion.
But on the other hand, in the new moon, the orbital speed of the earth is maximum, and in the 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 removal of the moon from the earth is 10 percent, this can be compared by taking a cobblestone and a pebble on outstretched hands, and bringing them closer and further away by 10 percent, are tides possible with such mathematics. It is believed that in the new moon, the continents run into a tidal hump, at a speed of about 1600 kilometers an hour, is this possible.
There is an opinion 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 they all stopped at the same time, and where did the force that rotated the satellites go ... The 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 ebb and flow.
Calling tides, the phenomenon of horizontal and vertical movement of ocean waters, is not entirely true, for the reason that most whirlpools do not contact with coastline ocean... If you look at the Earth from the side of the Sun, whirlpools that are in the midnight and noon side of the earth are more active, since they are in the zone relative motion.
And when the whirlpool enters the zone of sunset and dawn and becomes an edge to the Sun, then the whirlpool falls into the power of the Coriolis forces and subsides. In the new moon, the tides increase and ebb for the reason that the orbital speed of the earth is maximum ...
Material sent by the author: Yusup Khizirov
In order to exhaust the main questions related to the existence of its satellite near the Earth - the Moon, we need to say a few words about the phenomenon of tides. It is also necessary to answer the last question raised in this book: where did the moon come from and what is its future? What is a tide?
During high tides on the shores of the open seas and oceans, water advances onto the shores. The low banks are literally overwhelmed by huge masses of water. Huge spaces are covered with water. The sea, as it were, protrudes from the shores and presses onto the land. The sea water is clearly rising.
At high tides (64) ocean-going deep-water vessels are free to enter relatively shallow harbors and estuaries flowing into the oceans.
The tidal wave is very high in some places, reaching a dozen or more meters.
Approximately six hours pass from the beginning of the rise of the water, and the tide is replaced by an ebb (65), the water begins to gradually
subside, the sea near the coast becomes shallow, and significant areas of the coastal strip are freed from water. Not long ago, steamboats sailed in these places, and now the inhabitants roam the wet sand and gravel and collect shells, algae and other "gifts" of the sea.
What explains these constant ebb and flow? They occur due to the attraction that the Moon exerts on the Earth.
Not only does the Earth pull the Moon towards itself, but the Moon also pulls the Earth. The gravity of the Earth affects the motion of the Moon, causing the Moon to move along a curved path. But at the same time, the attraction of the Earth somewhat changes the shape of the Moon. The parts facing the Earth are attracted by the Earth more strongly than other parts. Thus, the Moon should have a somewhat elongated shape towards the Earth.
The attraction of the moon also affects the shape of the earth. On the side facing this moment to the Moon, there is some swelling, stretching of the earth's surface (66).
The particles of water, being more mobile and having little cohesion, are more amenable to this attraction of the moon than particles of solid land. In this regard, a very noticeable rise in water in the oceans is created.
If the Earth, like the Moon, were always facing the Moon with the same side, its shape would be somewhat elongated towards the Moon, and there would be no alternating tides. But the Earth turns in different directions to all heavenly bodies, including the Moon (daily rotation). In this regard, a tidal wave, as it were, runs along the Earth, runs after the Moon, which raises the water of the oceans higher in the parts of the earth's surface facing it at the moment. High tides should alternate with low tides.
In a day, the Earth will make one rotation around its axis. Consequently, exactly one day later, the same parts of the earth's surface should face the Moon. But we know that the Moon manages to cover some part of its path around the Earth in a day, moving in the same direction as the Earth rotates. Therefore, the period is lengthened, after which the same parts of the Earth will be turned to the Moon. Thereby The cycle of ebb and flow does not occur in a day, but in 24 hours and 51 minutes. During this period of time, two high tides and two low tides alternate on Earth.
But why two and not one? We find an explanation for this by recalling once again the law of universal gravitation. According to this law, the force of attraction decreases with increasing distance, and, moreover, inversely proportional to its square: the distance doubles - the attraction decreases four times.
On the side of the Earth, directly opposite that which faces the Moon, the following occurs. Particles close to Earth's surface, are attracted by the Moon weaker than the inner parts of the Earth. They tend less towards the Moon than particles closer to it. Therefore, the surface of the seas here, as it were, lags somewhat behind the solid inner parts of the globe, and here, too, there is a rise of water, a water hump, a tidal height, approximately the same as on the opposite side. Here, too, the tidal wave runs into the low shores. Consequently, there will be a tide along the coasts of the oceans both when these coasts are turned towards the Moon, and when the Moon is in the opposite direction. Thus, there must be two high tides and two low tides on the Earth during the period of a complete rotation of the Earth around its axis.
Of course, the magnitude of the tide is also influenced by the attraction of the Sun. But although the Sun is colossal in size, it is, however, much further from the Earth than the Moon. Its tidal influence is less than the influence of the Moon by half (only 5/11 or 0.45 of the tidal influence of the Moon).
The magnitude of each tide also depends on the height at which the Moon is at a given time. At the same time, it is completely indifferent what phase the Moon has at this time and whether it is visible in the sky. The moon may not be visible at this moment, that is, it may be in the same direction as the sun, and vice versa. Only in the first case, the tide will generally be stronger than usual, since the attraction of the Sun is added to the attraction of the Moon.
The calculation shows that the tidal force of the Moon is only one nine-millionth of the force of gravity on Earth, that is, the force with which the Earth itself attracts. Of course, this attractive action of the Moon is negligible. The rise of water by several meters is also negligible in comparison with the equatorial diameter of the globe, equal to 12,756,776 m. But a tidal wave, even so small, is, as we know, very noticeable for the inhabitants of the Earth located near the coast of the oceans.