tide

periodic rise and fall of the ocean: High tide is at 6:03 p.m.; a current, tendency, or drift, as of events: A tide of fear could lead to war.
Not to be confused with:tied – bound, fastened, or attached with a rope or string drawn together and knotted: He tied the package securely.

tide¹

T0206500 (tīd)n.1. a. The periodic variation in the surface level of the oceans and of bays, gulfs, inlets, and estuaries, caused by gravitational attraction of the moon and sun.b. A specific occurrence of such a variation: awaiting the next high tide.c. Flood tide.2. Tidal force.3. a. Something that increases, decreases, or fluctuates like the waters of the tide: a rising tide of skepticism; the shifting tide of the battle.b. A large amount or number moving or occurring in a mass: an incoming tide of immigrants; a tide of angry letters.c. A surge of emotion: felt an irresistible tide of sympathy for the defendant. See Synonyms at flow.4. A time or season. Often used in combination: eventide; Christmastide; Shrovetide.5. A favorable occasion; an opportunity.v. tid·ed, tid·ing, tides v.intr.1. To rise and fall like the tide.2. Nautical To drift or ride with the tide: tided off the reef; tiding up the Hudson.v.tr. To carry along with the tide.Phrasal Verb: tide over To support through a difficult period: I asked for $100 to tide me over till payday.

[Middle English, from Old English tīd, division of time; see dā- in Indo-European roots.]

tide²

T0206500 (tīd)intr.v. tid·ed, tid·ing, tides Archaic To betide; befall.

[Middle English tiden, from Old English tīdan; see dā- in Indo-European roots.]

tide

(taɪd) n1. (Physical Geography) the cyclic rise and fall of sea level caused by the gravitational pull of the sun and moon. There are usually two high tides and two low tides in each lunar day. See also tide-generating force, neap tide, spring tide2. (Physical Geography) the current, ebb, or flow of water at a specified place resulting from these changes in level: the tide is coming in. 3. (Physical Geography) See ebb³, flood³4. a widespread tendency or movement: the tide of resentment against the government. 5. a critical point in time; turning point: the tide of his fortunes. 6. dialect Northern English a fair or holiday7. (in combination) a season or time: Christmastide. 8. rare any body of mobile water, such as a stream9. archaic a favourable opportunityvb10. to carry or be carried with or as if with the tide11. (intr) to ebb and flow like the tide[Old English tīd time; related to Old High German zīt, Old Norse tīthr time] ˈtideless adj ˈtideˌlike adj

tide

(taɪd) vb (intr) archaic to happen[Old English tīdan; related to Old Frisian tīdia to proceed to, Middle Low German tīden to hurry, Old Norse tītha to desire]

tide¹

(taɪd)

n., v. tid•ed, tid•ing. n. 1. the periodic rise and fall of the waters of the ocean and its inlets, produced by the attraction of the moon and sun, and occurring about every 12 hours. 2. the inflow, outflow, or current of water at any given place resulting from the waves of tides. 3. flood tide. 4. a stream or current. 5. anything that alternately rises and falls, increases and decreases, etc. 6. tendency or drift, as of events. 7. a season or period (usu. used in combination): Eastertide; eventide. 8. Archaic. a suitable time or occasion. v.i. 9. to flow as the tide. 10. to float or drift with the tide. v.t. 11. to carry, as the tide does. 12. tide over, to assist in getting over a period of difficulty or distress. [before 900; Middle English; Old English tīd time, hour, c. Old Saxon tīd, Old High German zīt, Old Norse tīth; akin to time]

tide²

(taɪd)

v.i. tid•ed, tid•ing. Archaic. to happen or befall. [before 1000; Middle English; Old English tīdan, akin to tīd time; see tide¹]

tide

(tīd) The regular rise and fall in the surface level of the Earth's oceans, seas, and bays caused by the gravitational attraction of the moon and to a lesser extent the sun. See also ebb tide, flood tide, neap tide, spring tide.

tide

billow - The swell on the ocean produced by the wind, or on a river or estuary by the tide or wind.
slack water, slack tide - Before any turn of the tide, there is a time of slack water or slack tide.
happy as a clam - Originally happy-as-a-clam-at-full-tide; it may refer to the fact that when the tide is full, nobody is digging clams.
tidy - Comes from tide, which in Old English meant "time period"; its original meaning was "timely, opportune."

Tide

a stream; a current of things or emotions.Examples: tide of blood; of emigration, 1830; of emotions; of events; of feelings; of upright freedom, 1519; of popular prejudice, 1777; of sorrows, 1738.

tide

Past participle: tided
Gerund: tiding

Imperative
tide
tide

Present
I tide
you tide
he/she/it tides
we tide
you tide
they tide

Preterite
I tided
you tided
he/she/it tided
we tided
you tided
they tided

Present Continuous
I am tiding
you are tiding
he/she/it is tiding
we are tiding
you are tiding
they are tiding

Present Perfect
I have tided
you have tided
he/she/it has tided
we have tided
you have tided
they have tided

Past Continuous
I was tiding
you were tiding
he/she/it was tiding
we were tiding
you were tiding
they were tiding

Past Perfect
I had tided
you had tided
he/she/it had tided
we had tided
you had tided
they had tided

Future
I will tide
you will tide
he/she/it will tide
we will tide
you will tide
they will tide

Future Perfect
I will have tided
you will have tided
he/she/it will have tided
we will have tided
you will have tided
they will have tided

Future Continuous
I will be tiding
you will be tiding
he/she/it will be tiding
we will be tiding
you will be tiding
they will be tiding

Present Perfect Continuous
I have been tiding
you have been tiding
he/she/it has been tiding
we have been tiding
you have been tiding
they have been tiding

Future Perfect Continuous
I will have been tiding
you will have been tiding
he/she/it will have been tiding
we will have been tiding
you will have been tiding
they will have been tiding

Past Perfect Continuous
I had been tiding
you had been tiding
he/she/it had been tiding
we had been tiding
you had been tiding
they had been tiding

Conditional
I would tide
you would tide
he/she/it would tide
we would tide
you would tide
they would tide

Past Conditional
I would have tided
you would have tided
he/she/it would have tided
we would have tided
you would have tided
they would have tided

Thesaurus

Noun	1.	tide - the periodic rise and fall of the sea level under the gravitational pull of the moonperiodic event, recurrent event - an event that recurs at intervalshigh tide, high water, highwater - the tide when the water is highestlow tide, low water - the lowest (farthest) ebb of the tideebbtide - the tide while water is flowing outrising tide, flood tide, flood - the occurrence of incoming water (between a low tide and the following high tide); "a tide in the affairs of men which, taken at the flood, leads on to fortune" -Shakespearelee tide, leeward tide - a tide that runs in the same direction as the wind is blowing; "a leeward tide is dangerous for small boats"slack tide, slack water - the occurrence of relatively still water at the turn of the (low) tidetidal current, tidal flow - the water current caused by the tidesrip current, riptide - a strong surface current flowing outwards from a shoreundertide, undercurrent - a current below the surface of a fluid
	2.	tide - something that may increase or decrease (like the tides of the sea); "a rising tide of popular interest"variation, fluctuation - an instance of change; the rate or magnitude of change
	3.	tide - there are usually two high and two low tides each daylunar time periodperiod, period of time, time period - an amount of time; "a time period of 30 years"; "hastened the period of time of his recovery"; "Picasso's blue period"
Verb	1.	tide - rise or move forward; "surging waves"surgecourse, flow, run, feed - move along, of liquids; "Water flowed into the cave"; "the Missouri feeds into the Mississippi"ebb, ebb away, ebb down, ebb off, ebb out - flow back or recede; "the tides ebbed at noon"
	2.	tide - cause to float with the tidefloat - set afloat; "He floated the logs down the river"; "The boy floated his toy boat on the pond"bridge over, tide over, keep going - suffice for a period between two points; "This money will keep us going for another year"
	3.	tide - be carried with the tidebe adrift, drift, float, blow - be in motion due to some air or water current; "The leaves were blowing in the wind"; "the boat drifted on the lake"; "The sailboat was adrift on the open sea"; "the shipwrecked boat drifted away from the shore"

tide

noun1. current, flow, stream, course, ebb, undertow, tideway They used to sail with the tide.2. course, direction, trend, current, movement, tendency, drift They talked of reversing the tide of events.tide someone over keep you going, see you through, keep the wolf from the door, keep your head above water, bridge the gap for He wanted to borrow some money to tide him over.

tide

nounSomething suggestive of running water:current, drift, flood, flow, flux, rush, spate, stream, surge.

Translations

潮水潮汐

tide

(taid) noun the regular, twice-a-day ebbing and flowing movement of the sea. It's high/low tide; The tide is coming in / going out.潮汐ˈtidal adjective of or affected by tides. tidal currents; a tidal river. 潮汐的，受潮汐影响的 tidal wave an enormous wave in the sea, caused by an earthquake etc. 海啸

tide

→ 潮水zhCN

When is high tide? → 会涨潮吗？

tide

tide,

alternate and regular rise and fall of sea levelsea level,
the level of the sea, which serves as the datum used for measurement of land elevations and ocean depths. Theoretically, one would expect sea level to be a fixed and permanent horizontal surface on the face of the earth, and as a starting approximation, this is true.
..... Click the link for more information. in oceans and other large bodies of water. These changes are caused by the gravitational attraction of the moon and, to a lesser extent, of the sun on the earth. More generally, tides are the deformations of celestial bodies from a perfectly spherical shape that result from stresses created by their mutual gravitational attraction (see gravitationgravitation,
the attractive force existing between any two particles of matter. The Law of Universal Gravitation

Since the gravitational force is experienced by all matter in the universe, from the largest galaxies down to the smallest particles, it is often called
..... Click the link for more information. ). Another way of viewing the tide is as the longest possible ocean wave, one which stretches all the way around the earth. The tide regarded as a wave is sometimes referred to as a tidal wavetidal wave,
term properly applied to the crest of a tide as it moves around the earth. The wavelike upstream rush of water caused by the incoming tide in some locations is known as a tidal bore.
..... Click the link for more information. , although this term has been commonly applied to the shock wave propagated by an underwater earthquake. (To avoid confusion, such shock waves are now called tsunamistsunami
, series of catastrophic ocean waves generated by submarine movements, which may be caused by earthquakes, volcanic eruptions, landslides beneath the ocean, or an asteroid striking the earth. Tsunamis are also called seismic sea waves or, popularly, tidal waves.
..... Click the link for more information. , their Japanese name, or seismic sea waves.) Numerous schemes have been proposed to harness the earth's tides, especially in various estuaries, as a practical source of power, but none as yet have proved economically or technologically feasible.

Tidal Effect on the Earth

Tides are raised in the earth's solid crust and atmosphere as well as in the oceans. Every body in the universe has some tidal effect, however small, on every other body. This effect is directly proportional to the mass of the body causing the tide but inversely proportional to the cube of the distance between the bodies. The earth's nearby moon is about 2.17 times as effective as the more massive sun in raising tides on the earth, even though the sun exerts a much greater total force on the earth than does the moon. Thus, the moon's proximity explains its dominant role in creating tides.

Direct and Indirect Tides

At any given time, there are two high tides on the earth, the direct tide on the side facing the moon and the indirect tide on the opposite side. As the earth rotates on its axis, the location of the two diametrically opposed tidal bulges varies on the earth's surface. The earth's rotation and the moon's revolution, which have the same direction, bring each point on the earth opposite the moon once every 24 hr and 50 min. Therefore, the average interval between direct and indirect high tides is about 12 hr and 25 min. In many places along the Atlantic coasts of N America and Europe, the two daily low tides are of nearly equal duration and magnitude, called semidiurnal tides.

In certain shallow seas and narrow estuaries, the tides differ from this simple pattern. For example, in certain regions such as the Pacific coast of N America, one of the two daily tides is appreciably higher than the other or the interval between successive tides is unequal; these are called mixed tides. In other regions, such as the Gulf of Mexico, there is only one high tide per day called a diurnal tide, with a period of 24 hr and 50 min.

The Magnitude and Effects of Tidal Ranges

The range of the tides is the difference in sea level between high and low tides. Spring tide, having the maximum range, occurs during the full moon when the earth is between the moon and the sun, and new moon when the moon is between the earth and the sun. At these times in the lunar cycle when the moon, earth, and sun are aligned the condition is known as syzygy. The term king tide is used in some regions to describe the highest tides of the year. Neap tide, having the minimum range, occurs during the moon's first and last quarters, when the moon, earth, and sun form a right angle. The typical tidal range in the open ocean is 2 ft (0.61 m) but is much greater near the coast. Tidal ranges vary around the world and average about 6 to 10 ft (2 to 3 m). The world's widest tidal range occurs in the Bay of Fundy, in E Canada, where the sea level changes by 40 ft (12 m) during the day, while the Mediterranean, Baltic, and Caribbean Seas are relatively tideless.

As the tides change, currents must flow to redistribute the ocean's water. Near the coast, the direction of the current changes every 6 1-4 hr from toward the shore (flood current) to away from the shore (ebb current). In the open ocean, the tidal currents are rotary, shifting through all directions of the compass in a period matching that of the local tide. When tidal currents flow into the mouth of a river, they speed up. In extreme cases, the tidal rise advances up the river as a solid wall of water often several feet high, a rare phenomenon called a tidal borebore,
inrush of water that advances upstream with a wavelike front, caused by the progress of incoming tide from a wide-mouthed bay into its narrower portion. The tidal movement tends to be retarded by friction as it reaches the shallower water and meets the river current; it
..... Click the link for more information. . During times of high tide accompanied by high wind and low pressure, as during a hurricanehurricane,
tropical cyclone in which winds attain speeds greater than 74 mi (119 km) per hr. Wind speeds gust over 200 mi (320 km) per hr in some hurricanes. The term is often restricted to those storms occurring over the N Atlantic Ocean; the identical phenomenon occurring over
..... Click the link for more information. , a tidal surge can occur, causing coastal erosion, flooding, and damage to coastal cities.

The Prediction of Tides

Detailed prediction of ocean tides from theories of classical mechanics and hydrodynamics has not been entirely successful, largely because of complications introduced by the irregular shape of the ocean basins and coastlines. Useful results are obtained empirically by analyzing records of previous tides at a particular location to predict future tides. The importance of tides for maritime activities has prompted the compilation of tide tables for harbors, which give the time and height of high water and low water based on past observations and corrected for the varying positions of celestial bodies.

Bibliography

See A. C. Redfield, Introduction to Tides (1982); D. Arnold, Tides and Currents (1987); G. Marchuk and B. A. Kagan, Dynamics of Ocean Tides (1989).

Tide

a periodic fluctuation of sea level (ocean tides) caused by the gravitational attraction of the moon and sun. Deformation of the solid body of the earth (bodily tides) and fluctuations of atmospheric pressure (atmospheric tides) are caused by the same gravitational attraction.

The gravitational action of the moon or sun produces tide-generating forces that represent the difference between the moon’s gravitational force acting on a particle—an element of the mass of water, earth, or air— located at any point on earth, such as on the surface, and the moon’s gravitational pull on a particle of the same mass at the earth’s center (see Figure 1). These forces are proportional to the mass of the moon (m) and the distance from the center of the earth (r), and inversely proportional to the cube of the distance from the earth to the moon (R); they also depend on the zenith distance of the moon (z).

Figure 1. Distribution of tide-generating forces at various points (A, B, C, and so on) on the earth’s surface caused by the moon’s gravitational pull; thin arrows indicate gravitational forces, broken arrows the subtracted force of gravity at the earth’s center (H), and thick arrows tidal forces

The vertical component of the tidal force (F_v) per unit of mass changes the force of gravity by

where G is the gravitational constant. The force of gravity on the earth’s surface diminishes by 0.1 milligal, or by 1 X 10^–7 of its own magnitude, when the moon is at its zenith or nadir, and increases by half this magnitude at the places on the earth where the moon is rising or setting at the moment under consideration.

The horizontal component of tide-generating forces is equal to 0 when the moon is at its zenith, nadir, or on the horizon and is maximal when the zenith distance of the moon is equal to 45°and reaches 0.08 milligal:

The tide-generating force produced by the sun is determined analogously, but because of the great distance (despite the significantly greater mass of the sun), this force is 2.16 times smaller on the average.

Because of the earth’s diurnal rotation and the movement of the earth, moon, and sun along their orbits, the tide-generating force at each point on the earth’s surface changes continuously in time and is never repeated exactly. Tidal forces may, however, be represented as the sum of a large number of strictly periodic components determined from the theory of movement of the moon around the earth and the earth around the sun. The tables compiled by the British scientist D. Cartwright (1973) contain about 500 items. These periodic tidal forces are divided into four types. Long-period tides produce the greatest fluctuations of level surface at the poles, half this value at the equator, and no fluctuation at latitudes of ± 35.3°.

Long-period tides include tides with intervals of 18.6 years, one year, six months, one month, and two weeks (Mf). These tides periodically change the oblateness of the earth and the earth’s polar moment of inertia and angular velocity of rotation. Diurnal tides arise as the result of nonconformity of the equator’s plane with the plane of the lunar orbit and the ecliptic plane. They produce the greatest rises and falls of bodily tides at latitudes of ± 45°and no changes at the poles and the equator. The chief diurnal tides are the lunar tidal constituent O₁ with an interval of 25.8hours and the lunisolar constituent K₁ with an interval of 23.9 hours. Semidiurnal tides produce maximum rises and falls for static tides at the equator and no changes at the poles. The chief semidiurnal tidal constituents are the lunar constituent M₂ with an interval of 12.4 hours and the solar constituent S₂ with an amplitude approximately half as great and an interval of 12 hours. Short-period constituents have intervals of eight hours and less.

N. N. PARIISKII

Ocean tides. Changes in the tide-generating force cause changes in the gravitational force and in the magnitude and direction of the horizontal components of tidal forces and, consequently, in the direction of the plumb line as well. Influenced by these forces, the surface of oceans is impelled toward a position perpendicular to the plumb line, that is, varying in time at each point on earth. If the entire earth were covered by oceans and the water masses were able to achieve a state of equilibrium, as was initially assumed in Newton’s static theory of the tides, the moon’s influence would cause the spherical surface of the ocean to shift and assume the form of an elongated ellipsoid with the major axis directed toward the moon. Added to these shifts would be shifts corresponding to analogous ellipsoid deformations with the major axis directed toward the sun. The maximal rises and falls in sea level would then be only 0.5 m.

In actuality, the ocean does not cover the entire earth, and as the tidal wave moves it encounters obstacles in the form of continents and undergoes friction at the ocean bottom. Thus, reverse currents arise. As a result, the distributions of the amplitudes and phases of different tidal waves differ radically from the corresponding values presented in the static theory. Hence, the magnitude and nature of tides depend not only on the mutual position of the earth, moon, and sun but also on geographic latitude, the sea’s depth, and the configuration of the shoreline. In 1775, P. Laplace developed a dynamic theory of the tides based on the general equations of hydrodynamics. This theory made it possible to calculate the movement of tidal waves in the seas and oceans.

The greatest elevation of the water is called high water and the low stage is called low water. When the height of ocean tides far from the continents is of the order of 1 m, the difference between successive high and low waters along the coast may be very great. In the Bay of Fundy off the Atlantic coast of Canada, for example, the height of tides reaches 18 m, and in Frobisher Bay off Baffin Island and at certain points along the English Channel it reaches 15 m. Tides reach 13 m in Penzhina Bay off the northeastern coast of the Sea of Okhotsk and 10 m in Mezen’ Inlet of the White Sea. A tidal wave entering the mouth of a river may cause the formation of a steep wave.

Tide tables are published in the USA, USSR, Great Britain, Japan, and other countries to assist navigation, These tables contain figures on the height of tides in relevant ports for every hour of the year.

The movement of tidal waves on the high seas is determined by solving Laplace’s hydrodynamic differential equations on a computer with due regard for the configuration of the shoreline, the distribution of ocean depth, and the laws of friction against the ocean bottom. The solving of these equations makes it possible to prepare cotidal maps of the world’s oceans. Curves called cotidal lines are drawn on these maps to connect the points of a wave with identical phase, for example, the position of the crest of the given tidal wave for each hour. Another system of curves connects points with identical amplitude for the given wave. The most detailed cotidal maps for the four basic tidal waves M₂, S₂, K₁, and O₁ were compiled by K. T. Bogdanov and V. A. Magarik in the USSR. Ocean tides deflect the elastic body of the earth with their pressure, and therefore a familiarity with cotidal maps is essential when interpreting observations of bodily tides.

B. L. LAGUTIN

Bodily tides. The earth too is deformed through the action of tidal forces; these deformations are called bodily or elastic tides. The movement of elastic tidal waves causes vertical displacements of the earth’s surface reaching 50 cm when the moon and sun are positioned at the zenith or nadir and horizontal displacements reaching 5 cm. Tidal changes in the force of gravity at the equator reach 0.25 milligal, changes in the plumb line reach 0.01”, changes in the slopes of the earth’s surface— that is, in the angle between the earth’s surface and the plumb line— reach 0.02”, and tidal extensions and compressions of the earth’s surface layers are of the order of 10^–8. Volumetric deformations during bodily tides are manifested by periodic changes in the water level of pits and wells and in the level of lava in volcanoes, as well as by changes in the flow of some springs. Long-period tides deform the earth and change its rotational velocity. This is revealed by comparing astronomical time, determined on the basis of the earth’s rotation, with atomic time. The magnitude of all these tidal effects depends on the internal structure of the earth, that is, on the distribution of densities and of the elastic properties of different layers of the earth at all depths, from the surface to the center. Thus, observations of bodily tides make it possible to study the internal structure of the earth.

The theory relating the observed phenomena of bodily tides to the internal structure of the earth was developed by G. Takeuchi (Japan), H. Jeffreys (Great Britain), and R. Vicente (Portugal) and most extensively by M. S. Molodenskii. Specifically, the phenomenon of resonance between certain diurnal bodily tidal waves (K₁ and others) and the diurnal nutation of the earth was theoretically predicted as a result of the liquid state of the earth’s core. This theory was confirmed by observations of tidal changes in the force of gravity and in tilts.

Measurements of tidal changes in the force of gravity as well as the study of the global characteristics of the earth’s structure make it possible to study deep-seated regional irregularities in the earth’s mantle. These data are essential for gravimetric surveying for geodetic purposes, in geophysical exploration of useful minerals, and in the study of temporary changes in the force of gravity. Measurements of tidal tilts indicate that these tilts depend on local characteristics of the structure of the earth’s crust; such measurements can be utilized in the study of the block structure of the crust and of deep-seated fractures.

N. N. PARIISKII

Atmospheric tides. Together with diurnal fluctuations in air temperature, the atmosphere experiences very minor diurnal and relatively intensive semidiurnal changes in surface atmospheric pressure. It is difficult to identify such changes when there are intensive and irregular changes in weather. These variations are greatest in the tropical zone (about 1 millibar for the semidiurnal component) and decrease sharply in the temperate and high latitudes. Although the tidal forces of the moon are more than twice as great as those of the sun, solar tides predominate over lunar tides in the atmosphere, unlike tides in the sea and earth. Recent investigations of the upper atmosphere have explained this. The atmospheric tides, with an interval equal to half of the solar day, are caused primarily by the thermal, not gravitational, effect of the sun on the atmosphere. Ultraviolet solar radiation absorbed by the ozone in the stratosphere causes these layers of the atmosphere to become warm. This in turn stimulates fluctuations of such meteorological elements as pressure, temperature, density, and wind velocity; the fluctuations have such intervals as 24 and 12 hours. Most of the energy of the diurnal component is exerted on waves that are not transmitted from the upper atmosphere to the earth. This explains the very minor diurnal fluctuation of atmospheric pressure at the earth’s surface. By contrast, the semidiurnal fluctuations are transmitted to the earth and therefore their amplitude at the earth’s surface is much greater.

Atmospheric tides play an important part in the dynamics of the upper atmosphere. Diurnal and semidiurnal changes in parameters at great altitudes are so large that without a knowledge of them it is impossible to calculate the movement of man-made objects in the upper atmosphere.

E. P. CHUNCHUZOV

Cosmogonic role of tides. The existence of friction or viscosity in the case of bodily tides and the presence of complex continental boundaries in the case of sea tides cause the tidal crest to be borne forward in the direction of the earth’s rotation with the crest’s axis not oriented exactly toward the tide-generating body. If this occurs when the planet revolves more rapidly than its satellite, as with the earth and the moon, the forces operating from the moon (the satellite) on the tidal deformation of the earth (the planet) produce a force couple that retards the earth’s rotation. On the other hand, the action of tidal deformation on the moon causes the moon (the satellite) to move away from the earth. This secular retardation of the earth’s rotation was predicted long ago by G. Darwin.

Modern calculations of tidal retardation of the earth’s rotation indicate that most of the retardation is caused by ocean tides.

Bodily tides also retard the earth’s rotation, but much less than ocean tides. The total tidal retardation of the earth’s rotation should be approximately 3.5 msec per century, although astronomical observations indicate that during the last 2,000 years the day has grown longer by an average of 2.0 msec per century. Therefore, there are factors, as yet unexplained, that are accelerating the earth’s rotation by approximately 1.5 msec per century. Under the influence of tides, the moon is moving away from the earth at a rate of 3 cm a year. The influence of tides causes the moon to face the earth with one side and also causes the slowness of Mercury’s rotation. Cosmogony studies the effect of tides on changes in the moon’s orbit— its positions and dimensions— relative to the earth.

The relation between fluctuations in sea level and phases of the moon was observed in ancient times. The first static theory was devised by Newton (1688) and developed by his followers D. Bernoulli, C. Maclaurin, and L. Euler. Laplace’s dynamic theory of the tides (1775) was refined by the British scientists G. Airy (1848), W. Thomson (Lord Kelvin, 1895), and G. Darwin. Numerical methods of predicting sea tides were refined by the British scientists A. Doodson (1928) and D. Cartwright (1973). Methods of analyzing bodily tides were developed by Doodson, R. Lecolase (France), B. P. Pertsev and P. S. Matveev (USSR), and A. P. Venedikov (Bulgaria). The evolutionary and cosmogonic importance of tides was first studied by G. Darwin (1911).

The first observations of tides in Russia date from the early 18th century. In 1848, F. P. Litke published a cotidal map of the Barents Sea. A. M. Bukhteev and V. S. Stakhevich worked on observations of tides that were made until 1907. The works of the Soviet scientists Iu. M. Shokal’skii, V. V. Shuleikin, L. N. Sretenskii, N. E. Kochin, N. P. Vladimirskii, A. I. Duvanin, B. A. Kochan, K. R. Bogdanov, and V. A. Magarik are devoted to the study of sea tides. A. Ia. Orlov initiated the systematic study of bodily tides in the USSR, using tiltmeters at first and later gravimeters; Orlov established the Poltava Gravimetric Observatory for this purpose. The works of such Soviet scientists as M. S. Molodenskii and N. N. Pariiskii have contributed substantially to the study of bodily tides.

The cosmogonic significance of tides and their effect on the moon’s orbit have been studied by the American scientists G. J. F. MacDonald, P. Goldreich, and W. Cowell and by the Soviet scientists A. S. Monin and E. L. Ruskol.

N. N. PARIISKII

REFERENCE

Shokal’skii, Iu. M. Okeanografiia. Leningrad, 1959.
Duvanin, A. I. Prilivy v more. Leningrad, 1960.
Darwin, G. H. Prilivy i rodstvennye im iavleniia v solnechnoi sisteme. Moscow-Petrograd, 1923. (Translated from English.)
Lamb, H. Gidrodinamika. Moscow-Leningrad, 1947. (Translated from English.) Chapter 8.
Molodenskii, M. S. “Uprugie prilivy, svobodnaia nutatsiia i nekotorye voprosy stroeniia Zemli.” Tr. Geofizicheskogo in-ta AN SSSR, 1953, no. 19.
Melchior, P. Zemnye prilivy. Moscow, 1968. (Translated from English.)
Pariiskii, N. N., M. V. Kuznetsov, and L. V. Kuznetsova. “O vliianii okeanicheskikh prilivov na vekovoe zamedlenie vrashcheniia Zemli.” Fizika zemli, 1972, no. 2, page 12.
Siebert, M. “Atmospheric Tides.” In Advances in Geophysics, vol. 7. New York-London, 1961.

tide

[tīd] (oceanography) The periodic rising and falling of the oceans resulting from lunar and solar tide-producing forces acting upon the rotating earth.

tide

1. the cyclic rise and fall of sea level caused by the gravitational pull of the sun and moon. There are usually two high tides and two low tides in each lunar day 2. the current, ebb, or flow of water at a specified place resulting from these changes in level 3. See ebb (sense 3) and flood (sense 3)

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Tidal Effect on the Earth

Direct and Indirect Tides

The Magnitude and Effects of Tidal Ranges

The Prediction of Tides

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Synonyms for tide

noun current

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noun course

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phrase tide someone over

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noun something suggestive of running water

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noun the periodic rise and fall of the sea level under the gravitational pull of the moon

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noun something that may increase or decrease (like the tides of the sea)

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noun there are usually two high and two low tides each day

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verb rise or move forward

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verb cause to float with the tide

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verb be carried with the tide

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