Tides explained Yet More... Tides Most people grow up thinking that the tides are caused by the moon, and indeed that gravitational 'pull' of the moon is a major factor, as is the gravitational effect of the sun but there is another major factor, which is less often mentioned, and that is the force created by the rotation of the earth itself. So the diagram on the left shows how the water on the earth gets pulled into a bulge one way by the moon's gravity and into a bulge on the opposite side by the rotational force of the earth. As the earth rotates on its axis once every 24 hours, if the moon stood still then the moon will be overhead and 'underfoot' once in every 24 hours giving (in most places) 2 high and 2 low tides a day, but as the moon is also orbiting in the same direction as the earth revolves it actually takes about 24 hours and 50 minutes for the moon to be in the same place overhead. So the period from one high tide to the next is about 12 hours 25 minutes.

Spring Tides When the sun, moon and earth all line up at new (as in the picture) or full moon then we get the highest (and indeed lowest) tides which are called 'spring' tides (nothing to do with the time of year!). In fact it takes a bit of time for the enormous mass of water to move, so the spring tide will actually occur a couple of days after the new (or full) moon, so the picture on the left is a simplification. You can find more on ( moon phases here ) Because of the tilt of the earth on its axis, at the equinox the sun appears to be over the equator and if there is a new or full moon at about the same time then all the forces contrive to create the highest of high tides and if the moon is also at perigee (closest to the earth in its orbit) then that will produce the biggest tides of all.

Neap Tides When the moon is at first or third quarter (you can find more on moon phases here ) then the moon and sun are exerting forces from two different directions and the overall effect on the water is less, so the high tides are lower than average and the low tides are higher than the average and we call these low tides 'neap' tides. The word 'neap' is thought to have originated from the Middle English Word 'neep' meaning small. Other Factors and Facts Although the sun, the moon and the rotation of the earth are the major forces involved in creating the tides the local conditions such as the shoreline and the contour of the ocean floor also have an effect. Because of this not everywhere has 2 tides a day - there are some places that experience what is known as a double-high water (e.g. Southampton) or double-low water (e.g. Portland). The highest tides of all (17m) occur in Canada and after a long running dispute between the famous tides of the Bay of Fundy and those of Ungava Bay on the northern coast of Quebec, the Canadian Hydrographic Service has declared a draw.

Most people think of the Mediterranean area as being without tides and it is true that the tides there are very small, and can often go unnoticed as atmospheric conditions and headwinds can attenuate the effect of these tides making them difficult to see. The very smallest tidal ranges (actually 0) are found in the Adriatic and South of Sicily. "Everything has a natural explanation. The moon is not a god, but a great rock, and the sun a hot rock. " Anaxagoras "I think that when NASA works on a moon shot, they know too well that all of the people working on it must do their job at 110 percent. Sometimes they probably put in 18 hour days, but they're aiming for the moon, and that's what counts. " Marvin Hamlisch Tides, and the pull of the moon and sun | Earth | EarthSky Tides, and the pull of the moon and sun By Deborah Byrd in Earth | April 7, 2016 The sun, the moon, the shape of a beach and larger coastline, the angle of a seabed leading up to land, and the prevailing ocean currents and winds all affect the height of the tides.

This beautiful image is from EarthSky Facebook friend John Lloyd Griffith We all know the moon is primarily responsible for the rising and falling of ocean tides. In most places, but not everywhere, there are two high tides and two low tides a day. For any particular spot on Earth’s surface, the height of the tides and their fluctuation in time depends not only on the moon, but also on the sun – and also on the shape of the specific beach, the larger coastline, the angle of the seabed leading up to land, and the prevailing ocean currents and winds. The difference in height between high and low waters varies as the moon waxes and wanes from new to full and back to new again. The larger tides are called spring tides (nothing to do with season of spring). The smaller tides are called neap tides. Click the links below to learn more about the tides. Why are there two high tides and two low tides each day? Around each new moon and full moon – when the sun, Earth, and moon are located more or less on a line in space – the range between high and low tides is greatest. These are called spring tides.

Image via physicalgeography.net What are spring tides? Around each new moon and full moon, the sun, Earth, and moon arrange themselves more or less along a line in space. Then the pull on the tides increases, because the gravity of the sun reinforces the moon’s gravity. In fact, the height of the average solar tide is about 50% the average lunar tide. Thus, at new moon or full moon, the tide’s range is at its maximum. This is the spring tide: the highest (and lowest) tide. Spring tides are not named for the season. This is spring in the sense of jump, burst forth, rise. So spring tides bring the most extreme high and low tides every month, and they happen around full and new moon. What are perigean spring tides? When the new moon or full moon closely aligns with perigee – closest point to Earth in the moon’s orbit – then we have an extra-large perigean spring tides .

For example, in the year 2016, the April 7 new moon will closely align with perigee and the November 14 full moon will closely coincide with perigee, to bring forth perigean spring tides. When is the next supermoon? It’s when a spring tide coincides with a time of heavy winds and rain – flooding due to a weather extreme – that the most extreme flooding occurs. Around each first quarter moon and last quarter moon – when the sun and moon are at a right angle to Earth – the range between high and low tides is least. These are called neap tides. Image via physicalgeography.net What are neap tides? These sorts of tides occur halfway between each new and full moon – at the first quarter and last quarter moon phase – when the sun and moon are at right angles as seen from Earth. Then the sun’s gravity is working against the gravity of the moon, as the moon pulls on the sea. This is the neap tide: the tide’s range is at its minimum. Neap tides happen approximately twice a month, once around first quarter moon and once around last quarter moon.

There’s about a seven-day interval between spring tides and neap tides. Earth has two tidal bulges, one of the side of Earth nearest the moon (where the moon’s gravity pulls hardest), and the other on the side of Earth farthest from the moon (where the moon’s gravity pulls least). Why are there two high tides and two low tides each day? If the moon is primarily responsible for the tides, why are there two high tides and two low tides each day in most places, for example, the U.S. eastern seaboard? It seems as if there should just be one. If you picture the part of Earth closest to the moon, it’s easy to see that the ocean is drawn toward the moon. That’s because gravity depends in part on how close two objects are. But then why – on the opposite side of Earth – is there another tidal bulge, in the direction opposite the moon? It seems counterintuitive, until you realize that this second bulge happens at the part of Earth where the moon’s gravity is pulling the least. Looking for a tide almanac? EarthSky recommends … Earth spins once every 24 hours.

So a given location on Earth will pass “through” both bulges of water each day. Of course, the bulges don’t stay fixed in time. They move at the slow rate of about 13.1 degrees per day – the same rate as the monthly motion of the moon relative to the stars. Other factors, including the shape of coastlines, etc., also influence the time of the tides, which is why people who live near coastlines like to have a good tide almanac . Our Restless Tides - NOAA Tides & Currents Our Restless Tides Info and how to reach us Info and how to reach us × Chapter 6 - Prediction of Tides Chapter 4 - Variations in the Range of the Tides: Tidal Inequalities As will be shown in Fig. 6, the difference in the height, in feet, between consecutive high and low tides occurring at a given place is known as the range. The range of the tides at any location is subject to many variable factors. Those influences of astronomical origin will first be described. 1. Lunar Phase Effect: Spring and Neap Tides.

It has been noted above that the gravitational forces of both the moon and sun act upon the waters of the earth. It is obvious that, because of the moon's changing position with respect to the earth and sun (Fig. 3) during the monthly cycle of phases (29.53 days) the gravitational attraction of moon and sun may variously act along a common line or at changing angles relative to each other. When the moon is at new phase and full phase (both positions being called syzygy) the gravitational attractions of the moon and sun act to reinforce each other. Since the resultant or combined tidal force is also increased, the observed high tides are higher and low tides are lower than average. This means that the tidal range is greater at all locations which display a consecutive high and low water. Such greater-than-average tides resulting at the syzygy positions of the moon are know as spring tides - a term which merely implies a "welling up" of the water and bears no relationship to the season of the year. At first- and third-quarter phases (quadrature) of the moon, the gravitational attractions of the moon and sun upon the waters of the earth are exerted at right angles to each other.

Each force tends in part to counteract the other. In the tidal force envelope representing these combined forces, both maximum and minimum forces are reduced. High tides are lower and low tides are higher than average. Such tides of diminished range are called neap tides, from a Greek word meaning "scanty". 2. Parallax Effects (Moon and Sun). Since the moon follows an elliptical path (Fig. 4), the distance between the earth and moon will vary throughout the month by about 31,000 miles. The moon's tide-producing force acting on the earth's waters will change in inverse proportion to the third power of the distance between the earth and moon, in accordance with the previously mentioned variation of Newton's Law of Gravitation. Once each month, when the moon is closest to the earth (perigee), the tide-generating forces will be higher than usual, thus producing above-average ranges in the tides. Approximately two weeks later, when the moon (at apogee) is farthest from the earth, the lunar tide-raising force will be smaller, and the tidal ranges will be less than average.

Similarly, in the earth-sun system, when the earth is closest to the sun (perihelion), about January 2 of each year, the tidal ranges will be enhanced, and when the earth is farthest from the sun (aphelion), around July 2, the tidal ranges will be reduced. The Lunar Parallax and Solar Parallax Inequalities FIGURE 4 Both the Moon and the Earth revolve in elliptical orbits and the distances from their centers of attraction vary. Increased gravitational influences and tide-raising forces are produced when the Moon is at position of perigee, its closest approach to the Earth (once each month) or the Earth is at perihelion, its closest approach to the Sun (once each year). This diagram also shows the possible coincidence of perigee with perihelion to produce tides of augmented range. When perigee, perihelion, and either the new or full moon occur at approximately the same time, considerably increased tidal ranges result. When apogee, aphelion, and the first- or third-quarter moon coincide at approximately the same time, considerably reduced tidal ranges will normally occur. 3. Lunar Declination Effects: The Diurnal Inequality.

The plane of the moon's orbit is inclined only about 5o to the plane of the earth's orbit (the ecliptic) and thus the moon monthly revolution around the earth remains very close to the ecliptic. The ecliptic is inclined 23.5o to the earth's equator, north and south of which the sun moves once each half year to produce the seasons. In similar fashion, the moon, in making a revolution around the earth once each month, passes from a position of maximum angular distance north of the equator to a position of maximum angular distance south of the equator during each half month. (Angular distance perpendicularly north and south of the celestial equator is termed declination.) twice each month, the moon crosses the equator. In Fig. 5, this condition is shown by the dashed position of the moon. The corresponding tidal force envelope due to the moon is depicted, in profile, by the dashed ellipse.

The Moon's Declination Effect (Change in Angle With Respect to the Equator) and the Diurnal Inequality; Semidiurnal, Mixed, and Diurnal Tides FIGURE 5 A north-south cross-section through the Earth's center; the ellipse represents a meridian section through the tidal force envelope produced by the Moon. Since the points A and A' lie along the major axis of this ellipse, the height of the high tide represented at A is the same as that which occurs as this point rotates to position A' some 12 hours later. When the moon is over the equator - or at certain other force-equalizing declinations - the two high tides and two low tides on a give day are at similar height at any location. Successive high and low tides are then also nearly equally spaced in time, and occur twice daily. (See top diagram in Fig. 6.) This is known as semidiurnal type of tides. However, with he changing angular distance of the moon above or below the equator (represented by the position of the small solid circle in Fig.

5) the tidal force envelope produced by the moon is canted, and difference between the heights of two daily tides of the same phase begin to occur. variations in the heights of the tides resulting from the changes in the declination angle of the moon an in the corresponding lines of gravitational force action give rise to a phenomenon known as the diurnal inequality. In Fig. 5, point B is beneath a bulge in the tidal envelope. One-half day later, at point B' it is again beneath the bulge, but the height of the tide is obviously not as great as at B. This situation gives rise to a twice-daily tide displaying unequal heights in successive high or low waters, or in both pairs of tides. This type of tide, exhibiting a strong diurnal inequality, is known as a mixed tide. (See the middle diagram in Fig. 6.) Finally, as depicted in Fig. 5, the point C is seen to lie beneath a portion of the tidal force envelope. One-half day later, however, as this point rotates to position C', it is seen to lie above the force envelope. At this location, therefore, the tidal forces present produce only one high water and one low water each day.

The resultant diurnal type of tide is shown in the bottom diagram of Fig. 6. Principal Types of Tides The Moon And Tides Moon Tides How The Moon Affects Ocean Tides... The word "tides" is a generic term used to define the alternating rise and fall in sea level with respect to the land, produced by the gravitational attraction of the moon and the sun. To a much smaller extent, tides also occur in large lakes, the atmosphere, and within the solid crust of the earth, acted upon by these same gravitational forces of the moon and sun. What are Lunar Tides Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. But, the Earth is able to hold onto everything except the water. Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it. Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides.

Tides are the periodic rise and falling of large bodies of water. Winds and currents move the surface water causing waves. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Ocean levels fluctuate daily as the sun, moon and earth interact. As the moon travels around the earth and as they, together, travel around the sun, the combined gravitational forces cause the world's oceans to rise and fall. Since the earth is rotating while this is happening, two tides occur each day. What are the different types of Tides When the sun and moon are aligned, there are exceptionally strong gravitational forces, causing very high and very low tides which are called spring tides, though they have nothing to do with the season. When the sun and moon are not aligned, the gravitational forces cancel each other out, and the tides are not as dramatically high and low. These are called neap tides. Spring Tides When the moon is full or new, the gravitational pull of the moon and sun are combined.

At these times, the high tides are very high and the low tides are very low. This is known as a spring high tide. Spring tides are especially strong tides (they do not have anything to do with the season Spring). They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. Neap Tides During the moon's quarter phases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide. Neap tides are especially weak tides. They occur when the gravitational forces of the Moon and the Sun are perpendicular to one another (with respect to the Earth). Neap tides occur during quarter moons. The Proxigean Spring Tide is a rare, unusually high tide. This very high tide occurs when the moon is both unusually close to the Earth (at its closest perigee, called the proxigee) and in the New Moon phase (when the Moon is between the Sun and the Earth).

The proxigean spring tide occurs at most once every 1.5 years. High Tide / Low Tide Examples A view of the tides at Halls Harbour on Nova Scotia's Bay of Fundy. This is a time lapse of the tidal rise and fall over a period of six and a half hours. During the next six hours of ebb the fishermen unload their boats on the dock. That's a high tide every 12 and 1/2 hours! There are two high tides every 25 hours. A Few Facts About Lunar Tides The gravitational force of the moon is one ten-millionth that of earth, but when you combine other forces such as the earth's centrifugal force created by its spin, you get tides. The sun's gravitational force on the earth is only 46 percent that of the moon. Making the moon the single most important factor for the creation of tides. The sun's gravity also produces tides. But since the forces are smaller, as compared to the moon, the effects are greatly decreased. Tides are not caused by the direct pull of the moon's gravity. The moon is pulling upwards on the water while the earth is pulling downward.

Slight advantage to the moon and thus we have tides. Whenever the Moon, Earth and Sun are aligned, the gravitational pull of the sun adds to that of the moon causing maximum tides. Spring tides happen when the sun and moon are on the same side of the earth (New Moon) or when the sun and moon are on opposite sides of the earth (Full Moon). When the Moon is at first quarter or last quarter phase (meaning that it is located at right angles to the Earth-Sun line), the Sun and Moon interfere with each other in producing tidal bulges and tides are generally weaker; these are called neap tides. Spring tides and neap tide levels are about 20% higher or lower than average. Offshore, in the deep ocean, the difference in tides is usually less than 1.6 feet The surf grows when it approaches a beach, and the tide increases. In bays and estuaries, this effect is amplified. (In the Bay of Fundy, tides have a range of 44.6 ft.) The highest tides in the world are at the Bay of Fundy in Nova Scotia, Canada.

Because the earth rotates on its axis the moon completes one orbit in our sky every 25 hours (Not to be confused with moon's 27 day orbit around the earth), we get two tidal peaks as well as two tidal troughs. These events are separated by about 12 hours. Since the moon moves around the Earth, it is not always in the same place at the same time each day. So, each day, the times for high and low tides change by 50 minutes. The type of gravitational force that causes tides is know as "Tractive" force. FAQs About Lunar Tides From - "The Astronomy Cafe" Why are there no ocean tides at the equator? "Tides are a very complex phenomenon. For any particular location, their height and fluctuation in time depends to varying degrees on the location of the Sun and the Moon, and to the details of the shape of the beach, coastline, coastline depth and prevailing ocean currents. The tidal bulge of the Moon follows along the path on the earth's surface which intersects with the orbital plane of the Moon. This plane is tilted about 23 degrees with respect to the equatorial plane of the earth.

The result is that near the equator, the difference between high tide and low tide is actually rather small, compared to other latitudes. To see this, draw a circle inscribed in an ellipse, with the major axis of the ellipse rotated by 23 degrees with respect to the circle's horizontal diameter. Now measure the height of the elliptical contour just above the 'equator' of the circle. You will see that it is quite small compared to other positions on earth, particularly at latitudes of 23 degrees or so. Even larger differences can occur depending on the shape of a bay or inlet or continental shelf." - Dr. Odenwald's ASK THE ASTRONOMER Why are ocean tides so different everywhere? "Because they depend on many factors including the geometry of your local coastline, and exactly where the Sun and Moon are located. Also, like the surface of a vibrating drum, the world oceans have vibratory modes that get stimulated in changing ways from minute to minute. Finally, there are storms at sea and elsewhere which move large quantities of water. Detailed forecasts are available for high and low tides in all sea ports." - Dr.

Odenwald's ASK THE ASTRONOMER Why aren't the Atlantic and Pacific coast tides the same? "The nature of tides on the Earth's oceans is very complex. The oceans are, of course, being periodically 'forced' by a number of tidal sources including the Moon and the Sun, but this forcing has a number of different periods and harmonics. The two dominant periods are sue to the Sun and Moon, these are referred to as the S1 and M2 'modes' which have roughly 12 hour periods because they raise TWO water tides on the ocean diametrically opposite each other. But, for a variety of reasons, any given port will not have two high and two low tides each day; also called 'semi-diurnal tides'. A careful monitoring of the tides at any port for several years will show that in addition to the major modes, there are as many as 300 minor or 'harmonic' modes as well. The World Ocean is a complex dynamical system. The natural velocity of a water disturbance depends on the depth and salinity of the water at each point it passes.

When bodies of land circumscribe bodies of water, they produce a collection of resonating systems that favor water oscillations with certain frequencies over others. From among the 300+ harmonics that can be measured, every port and coastal location has its own unique signature depending on its latitude, longitude, water depth and salinity. The result is that the 'two high two low' tide rule can be strongly modified so that the time between successive high tides can be greater than or less that 12 hours in many cases. The result is that for some locations, there can be days when only one high tide occurs. Looking at the Atlantic and Pacific Coast tide tables for 1995, the data for the various 'Standard Ports' showed that virtually all days had two high tides and two low tides in San Diego, San Francisco, New York and Charleston. There were, however a few days every few months when only a single high tide occurred." - Dr. Odenwald's ASK THE ASTRONOMER What is a Proxigean Spring Tide?

"The Moon follows an elliptical path around the Earth which has a perigee distance of 356,400 kilometers, which is about 92.7 percent of its mean distance. Because tidal forces vary as the third power of distance, this little 8 percent change translates into 25 percent increase in the tide- producing ability of the Moon upon the Earth. If the lunar perigee occurs when the Moon is between the Sun and the Earth, it produces unusually high Spring high tides. When it occurs on the opposite side from the Earth that where the Sun is located ( during full moon) it produces unusually low, Neap Tides. The High, High Tide is called the Proxigean Spring Tide and it occurs not more than once every 1.5 years. Some occurrences are more favorable that others. A very interesting book "Tidal Dynamics" by Fergus J. Wood, published in 1986 by Reidel Publishing Company, talks at great length about these tides, and their environmental consequences.

Because of the gravitational nature of the interaction between the Earth, the Moon, and the water on the Earth, there is a curious amplification event called 'evection' that occurs when the Moon is at its closest 'perigee' distance called its 'proxigee'. The Moon draws even closer to the Earth than its ordinary perigee distance. Because of the complex dynamics of the Earth's oceans, their inertia, friction with the ocean floor, internal viscosity and the distribution of the continents, the maximum tides do not always coincide with the optimal times of proxigee. Still, these tides can produce enormous damage when all factors come together optimally. There are many recorded instances of unusually high storm or coastal flooding during the proxigean times. On January 9, 1974 the Los Angeles Times reported 'Giant Waves Pound Southland Coast". During the last 400 years, there have been 39 instances or 'Extreme Proxigean Spring Tides' where the tide-producing severity has been near the theoretical maximum. The last one of these was on March 7 1995 at 22:00 hours Greenwich Civil Time during a lunar Full Moon.

There were, in fact cases of extreme tidal flooding recorded during these particular spring tides which occur once every 31 years." - Dr. Odenwald's ASK THE ASTRONOMER If the Moon were to escape, what would happen to the Earth's oceans? "What happens is that the lunar water tides on the Earth go away, but the solar water tides still occur, but with about 1/3 or so the amplitude. There are still daily high and low tides, but they would be noticeably smaller. There would be no 'Spring' or 'Neap' tides, however."- Dr. Odenwald's ASK THE ASTRONOMER Why does the Moon produce TWO water tides on the Earth and not just one? "It is intuitively easy to understand why the gravitational pull of the Moon should produce a water tide on the Earth in the part of the ocean closest to the moon along the line connecting the center of the Moon with the center of the Earth. But in fact not one but TWO water tides are produced under which the Earth rotates every day to produce about two high tides and two low tides every day. How come?

It is not the gravitational force that is doing it, but the change in the gravitational force across the body of the Earth. If you were to plot the pattern of the Moon's 'tidal' gravitational force added to the Earth's own gravitational force, at the Earth's surface, you would be able to resolve the force vectors at different latitudes and longitudes into a radial component directed towards the Earth's center, and a component tangential to the Earth's surface. On the side nearest the moon, the 'differential' gravitational force is directed toward the Moon showing that for particles on the Earth's surface, they are being tugged slightly towards the Moon because the force of the Moon is slightly stronger at the Earth's surface than at the Earth's center which is an additional 6300 kilometers from the Moon. On the far side of the Earth, the Moon is tugging on the center of the Earth slightly stronger than it is on the far surface, so the resultant force vector is directed away from the Earth's center. The net result of this is that the Earth gets deformed into a slightly squashed, ellipsoidal shape due to these tidal forces.

This happens because if we resolve the tidal forces at each point on the Earth into a local vertical and horizontal component, the horizontal components are not zero, and are directed towards the two points along the line connecting the Earth and the Moon's centers. These horizontal forces cause rock and water to feel a gravitational force which results in the flow of rock and water into the 'tidal bulges'. There will be exactly two of these bulges. At exactly the positions of the tidal bulges where the Moon is at the zenith and at the nadir positions, there are no horizontal tidal forces and the flow stops. The water gets piled up, and the only effect is to slightly lower the weight of the water along the vertical direction. Another way of thinking about this is that the gravitational force of the Moon causes the Earth to accelerate slightly towards the Moon causing the water to get pulled towards the Moon faster than the solid rock on the side nearest the Moon. On the far side, the solid Earth 'leaves behind' some of the water which is not as strongly accelerated towards the Moon as the Earth is. This produces the bulge on the 'back side' of the Earth."- Dr. Odenwald's ASK THE ASTRONOMER What Causes Tides?

"There are several kinds of tides. The ones that break upon a beach every 10 seconds to a minute are caused by sea level disturbances out in the ocean produced by such things as storms. Also, the various circulation currents of sea water can have velocity components directed towards the land which will bring water up onto the beach. As this water travels towards the beach from deep water to shallow water, its amplitude will increase until it finally 'breaks' as a full-fledged breaker, suitable for surfing etc. Now, underlying this minute to minute activity is a slower water wave which causes an alternating pattern of high-tide, low-tide, high-tide, low-tide in most places on the Earth that are directly on the ocean. This roughly 6 hour cycle is caused by the gravitational tugging of the Moon upon the Earth. This 'tidal' pull causes the shape of the solid Earth to be not perfectly round by something like a few dozen yards over its entire 27,000 mile circumference. The Earth gets distorted a small bit, but because it is solid rock its a small effect. The water in the oceans, however, gets distorted into a roughly ellipsoidal ( football-like) shape with a much larger amplitude.

The orientation of this shape changes from minute to minute as the Moon orbits the Earth, which is why the high and low tide times change all the time. The Moon causes these tides by deforming the oceans, and as the Earth rotates under this ocean bulge, it causes a high tide to propagate onto beaches. Because there are two bulges, we get two high tides, and also two low tides each day. The Sun also causes tides on the Earth because even though it is so far away, it is very massive. These solar tides are about half as strong as the ones produced by the Moon, and they cause the so-called Spring tides and the Neap Tides. When the bulge of ocean water raised by the Moon is added the a similar tidal bulge raised by the Sun, you get a higher, high tide called the Spring Tide. When the solar low tide is added to the lunar low tide, you get the Neap Tide. There may be even weaker tides caused by the gravitational influences of the planets Mars and Venus, but they are probably lost in the daily noise of individual tides."- Dr.

Odenwald's ASK THE ASTRONOMER When the Earth, Moon and Sun are aligned for Spring Tides, are they highest at Full or New Moon? "Spring tides are about the same height whether at New or Full Moon, because the tidal bulge occurs on both sides of the Earth...the side toward the Moon ( or sun) and the side away from the Moon (or Sun). They will not be equally high because the distance between the Earth and Sun, and the Earth and Moon both vary and so will their tide producing effectiveness. The highest Spring tides occur when the Moon is at its closest to the Earth...the so-called Perigee Tide."- Dr.

Odenwald's ASK THE ASTRONOMER Tides at Menlo School - StudyBlue StudyBlue highest water levels during a day caused by the gravitational pull of the Moon low tide lowest water levels during a day when high tide is one-quarter of the way around Earth’s sphere Advertisement ) neap tide smallest tidal range in a lunar month occurring at the first- and third-quarter moons when the Sun and Moon are at 90o relative to each other, relative to Earth spring tide large tidal range that occurs when the Moon, Sun, and Earth area aligned; this happens at full and new moon phases tidal range difference of height between high and low tides tide regular rising and falling of Earth’s surface waters twice a tidal day as a result of the Moon’s and Sun’s gravitational attraction Advertisement * The material on this site is created by StudyBlue users. StudyBlue is not affiliated with, sponsored by or endorsed by the academic institution or instructor. Words From Our Students "StudyBlue is great for studying. I love the study guides, flashcards and quizzes. So extremely helpful for all of my classes!" Alice , Arizona State University "I'm a student using StudyBlue, and I can 100% say that it helps me so much.

Study materials for almost every subject in school are available in StudyBlue. It is so helpful for my education!" Tim , University of Florida "StudyBlue provides way more features than other studying apps, and thus allows me to learn very quickly!??I actually feel much more comfortable taking my exams after I study with this app. It's amazing!" Jennifer , Rutgers University "I love flashcards but carrying around physical flashcards is cumbersome and simply outdated. StudyBlue is exactly what I was looking for!" Justin , LSU The Moon and Tides The Moon and Tides No issues Abstract Have you ever wondered what causes the tides in Earth's oceans? In this astronomy project, you will discover the answer for yourself! You will investigate how the Sun and Moon control tides in Earth's oceans. Objective Use data from the U.S. Naval Observatory and National Oceanic and Atmospheric Administration (NOAA) to investigate the connection between the phases of the Moon and changes in the tides. Credits Sara Agee, PhD, and Terik Daly, Science Buddies Adobe® Reader® are registered trademarks of Adobe Systems Incorporated Cite This Page MLA Style Science Buddies Staff. "The Moon and Tides" Science Buddies. Science Buddies, 3 Oct.

2014. Web. 19 Jan. 2017 < APA Style Science Buddies Staff. (2014, October 3). The Moon and Tides. Retrieved January 19, 2017 from Share your story with Science Buddies! I Did This Project! Please log in and let us know how things went. Last edit date: 2014-10-03 Introduction If you have been to the seashore, you may have noticed that the water level changes throughout the day. Sometimes the water is high, and sometimes the water is low. This pattern of rising and falling sea level is known as the tides. When the water level is high, we call it high tide. When the water level is low, we call it low tide. In between high tide and low tide, tidal currents move water toward or away from the shore. Scientists have a special name for the difference in water level between high tide and low tide. They call it the tidal range.

For example, if the water is 75 centimeters (cm) deep at high tide and 25 cm deep at low tide, then the tidal range is 50 cm (75 cm - 25 cm = 50 cm). Figure 1, below, shows high tide and low tide at the Bay of Fundy, which is located between the Canadian provinces of New Brunswick and Nova Scotia. Figure 1. The Bay of Fundy has one of the largest tidal ranges in the world. The photo on the left shows the coast at high tide. The photo on the right shows the exact same place at low tide. The tidal range is the difference in water height between the left picture (high tide) and right picture (low tide). (Image credit: Wikimedia Commons user Samuel Wantman, 2013) Tides result from a gravitational tug-of-war between Earth, the Moon, and the Sun. The Moon's gravitational force is slightly stronger on the side of Earth that is closer to the Moon than it is on the side of Earth that is farther from the Moon. This small difference in the strength of the Moon's gravitational force pulls Earth's oceans into an elliptical shape.

As a result, water "piles up" in the oceans on opposite sides of Earth, as shown in Figure 2, below. The two long ends of the stretched-out, elliptical shape are called the tidal bulge. High tides happen close to where each end of the tidal bulge is located. Low tides happen in between, where the ocean is thinner, because of the pile-up of water at the tidal bulge. Figure 2. Without the Moon, Earth's outline would look like a circle if you were looking down on the North Pole. But because Earth does have a moon, differences in the gravitational forces exerted by the Moon stretch the oceans into an elliptical shape, creating a tidal bulge that sticks out beyond where the ocean would be if Earth didn't have a moon. Note: This image is not to scale. In reality, the tidal bulge is much smaller than shown here. The Moon is also much farther from Earth. The tidal bulge always points near an imaginary line connecting Earth and the Moon. As Earth rotates, different parts of Earth are affected by the tidal bulge. This is what makes the tides rise and fall.

In many places, there are two high tides and two low tides each day. Some places have two high tides and two low tides, but one of the pairs of high tides and low tides has a smaller tidal range than the other. In other places, there is only one high tide and low tide each day. These differences are often controlled by the shape of the seafloor and coastline in a particular place. The Sun also creates a tidal bulge because the Sun's gravitational force is a little bit stronger on the side of Earth that faces the Sun than it is on the side of Earth that faces away from the Sun. Depending on where the Moon is in its orbit around Earth, the tidal bulges made by the Moon and the Sun may line up in the same direction, or partially cancel one another. We can tell where the Moon is in its orbit by the phases of the Moon. The Moon has four primary phases: new, first quarter, full, and third quarter. As shown in Figure 3, below, the tidal bulges created by the Sun and the Moon line up in the same direction at the new moon and full moon, when the Sun, Earth, and Moon form a line. This creates a spring tide.

Spring tides have a larger-than-normal tidal range (higher high tides and lower low tides). When the Moon is at first quarter or third quarter, the Sun, Earth, and Moon form an "L" shape, and the tidal bulges of the Moon and the Sun make the shape of a plus sign (+). This creates a neap tide. Neap tides have a smaller-than-normal tidal range (lower high tides and higher low tides). Figure 3. (Top) Spring tides happen when the Sun, Earth, and Moon form a line, so the tidal bulge created by the Sun (shown in light yellow) and the tidal bulge created by the Moon (shown in light blue) both line up with each other. Spring tides have a bigger tidal range than normal. (Bottom) Neap tides happen when the Sun, Earth, and Moon form an "L" shape. Neap tides have a smaller tidal range than normal. Note: This image is not to scale. The Moon and Sun are much farther away from Earth than shown here. The Sun is also much larger.

In this astronomy science project, you will compare the tidal range at the full moon and first quarter moon to see just how much the phases of the Moon affect the tides in Earth's oceans. Terms and Concepts Questions What causes tides in Earth's oceans? When do the tidal bulges created by the Moon and Sun line up and increase tidal range? When do they form a "+" shape and partially cancel each other? What is the difference between a spring tide and a neap tide? If you were at the seashore and saw the Moon overhead, would the tide be high or low? Bibliography Stuart, F.L. (2000). Boat Safe Kids! How Does the Moon Affect Tides? Nautical Know How, Inc. Retrieved August 16, 2014, from Moon Connection Staff. (n.d.). Understanding the Moon Phases. MoonConnection. Retrieved August 16, 2014, from OneGeology Kids Staff. (n.d.). Tides. Retrieved August 16, 2014, from For help creating graphs, try this website: National Center for Education Statistics, (n.d.). Create a Graph.

Retrieved June 2, 2009, from News Feed on This Topic , , Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed Materials and Equipment Computer with internet access Lab notebook A program that can open PDF files, such as Adobe® Reader® (which is free to download) Graph paper and colored pencils (or you can use an online program, like Create a Graph ) Share your story with Science Buddies! I Did This Project! Please log in and let us know how things went. Experimental Procedure In this science project, you will gather data from two different sources. To keep your data organized, make two data tables like Tables 1 and 2, below, in your lab notebook. One data table will be for tides during the first quarter moon (neap tides). The second data table will be for tides during the full moon (spring tides). You will need about 13 rows in each data table. Tides During First Quarter Moons (Neap Tides) Date Table 2.

An example data table for recording dates, heights, and tidal ranges for spring tides (you will need to add more rows to your data table). It is time to start collecting data! Go to the U.S. Naval Observatory "Phases of the Moon" website, which has a calendar of the phases of the Moon. Type the current year (e.g., 2014) into the "Year" box. If the month and day are not already set to January 1st, click the "First of Year" button. Make sure "Number of Phases" is 50 and data format is "Displayed by phase". Click the "Get Data" button. This will take you to a new webpage that tells you when different phases of the Moon will happen (see Figure 4, below). Figure 4. Phases of the Moon calendar. For this project, you will need the dates of the first quarter and full moons. In 2014, for example, there was a first quarter moon on January 8th and a full Moon on January 16th.

Write the dates of all of the first quarter moons for the entire year in your data table titled "Tides During the First Quarter Moons". Write the dates of all of the full moons for the entire year in your data table titled "Tides During the Full Moons". Go to the NOAA Tide Predictions website, which predicts the timing and height of tides in a variety of places. Click the state or island you would like to see predictions for. Any state or island will work, so pick one that interests you. Next, click on the name of a station. This will open a page with predicted tide heights and times for that particular station. Download the tide predictions by clicking the orange "Annual PDF" button in the "Published Tide Tables Formats" box (outlined by a red box in Figure 5, below). Figure 5. Download tide predictions for the entire year by clicking on the orange "Annual PDF" button under the "Published Tide Table Formats" heading in the upper right corner of the website. Use the predictions in the "Annual PDF" to fill in the "Height of High Tide (cm)" and "Height of Low Tide (cm)" columns of your "Tides During First Quarter Moons" data table.

Find the dates on the tide table that match the dates of the first quarter moons you wrote in your data table. Write the height of the first high tide and first low tide for each of the dates in your data table. See Figure 6, below, for an example of where to find this data. Figure 6. In your data table, write the height of the first high tide and first low tide of each day with a full moon or first quarter moon. Be sure to record height in centimeters (cm) not feet (ft). On some days (like February 6, 2014), high tide will happen before low tide. On other days (such as March 16, 2014), low tide will happen first. So make sure you write tide heights in the correct columns of your data table. Do not worry if you see a negative number for a low tide (such as -9 cm on March 16, 2014); it just means the tide was very low that day.

Repeat the procedure in step 6 to fill in the "Height of High Tide (cm)" and "Height of Low Tide (cm)" columns of your second data table, "Tides During Full Moons." All of the columns in your data tables, except for the last one, should now be filled in. Finish your data tables by calculating the tidal range for each day, using Equation 1, below. Write the number in the "Tidal Range (cm)" columns. Equation 1: Now it is time to analyze your data. Make a graph with the date on the x-axis (horizontal) and tidal range on the y-axis (vertical), as shown in Figure 7, below. You can make a graph by hand, or use a program such as Create a Graph . Use one color to plot tidal range vs. the dates of the first quarter moon (the data points from Table 1). Use a different color to plot tidal range vs. the dates of the full moon (the data points from Table 2). Remember to include a legend on your graph explaining what the colors mean. Figure 7.

Example of a graph that plots the date of the first quarter or full moon on the x-axis and tidal range on the y-axis. What differences do you observe between the tidal ranges on days with first quarter moons and the days with full moons? What causes these differences? Share your story with Science Buddies! I Did This Project! Please log in and let us know how things went. Variations This experiment uses data generated by mathematical models of the tides. You could also do this project using your own observations. If you live near a marina, see if they have a tide gauge that you can use to make readings. You could also use a piece of wood secured to a bulkhead to track the height of the tide each day. To track the phases of the moon, keep a lunar logbook. Go outside each evening and draw the moon's appearance. How closely do your recorded measurements match the predicted data? If you do not live near the ocean, but want to use tide measurements (not predictions), you can use historical tide measurements as the source of data for your project. An internet search for historical tide measurements will bring up sources where you can find that type of information.

In addition to the gravitational pulls of the Moon and Sun, the shape of the seafloor and local geography affect the tides. Try doing this project with data from a few different places, such as an island in the Pacific Ocean, a state that borders the Gulf of Mexico, and a state that borders the Pacific Ocean. What differences in tidal range do you observe among these different locations? How might you explain the patterns at the different locations you selected? In this science project, you tracked tide height during the first quarter moon and full moon. How do the other phases of the moon affect the tide? Try an experiment comparing tidal range and lunar phase every day for a full lunar month. Can you observe a cycle or pattern? Share your story with Science Buddies! I Did This Project! Please log in and let us know how things went. If you like this project, you might enjoy exploring these related careers: Astronomer Astronomers think big! They want to understand the entire universe—the nature of the Sun, Moon, planets, stars, galaxies, and everything in between.

An astronomer's work can be pure science—gathering and analyzing data from instruments and creating theories about the nature of cosmic objects—or the work can be applied to practical problems in space flight and navigation, or satellite communications. Read more Geographer When you hear the word geography, you might think of maps and names of state capitals, but the work of geographers is much more than creating maps and identifying places. Geographers look at how people, places, and Earth are connected. They study the economy, social conditions, climate, and topography of a region to help answer questions in urban and regional planning, business, agriculture, and medicine. Read more Physicist Physicists have a big goal in mind—to understand the nature of the entire universe and everything in it! To reach that goal, they observe and measure natural events seen on Earth and in the universe, and then develop theories, using mathematics, to explain why those phenomena occur. Physicists take on the challenge of explaining events that happen on the grandest scale imaginable to those that happen at the level of the smallest atomic particles. Their theories are then applied to human-scale projects to bring people new technologies, like computers, lasers, and fusion energy.

Read more News Feed on This Topic , , Note: A computerized matching algorithm suggests the above articles. It's not as smart as you are, and it may occasionally give humorous, ridiculous, or even annoying results! Learn more about the News Feed Looking for more science fun? Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom. Tides | Define Tides at Dictionary.com 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 of the Sun. The maximum high tides (or spring tides) occur when the Moon and Sun are directly aligned with Earth, so that their gravitational pull on Earth's waters is along the same line and is reinforced. The lowest high tides (or neap tides) occur when the Moon and Sun are at right angles to each other, so that their gravitational pull on Earth's waters originates from two different directions and is mitigated. Tides vary greatly by region and are influenced by sea-floor topography, storms, and water currents.

See also ebb tide , flood tide, neap tide, spring tide. The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved. Tides Tides The Sun and Moon Affect the Oceans The moon is the primary tidal force. Share By Matt Rosenberg The gravitational pull of the moon and the sun creates tides on the earth. While tides are most commonly associated with oceans and large bodies of water, gravity creates tides in the atmosphere and even the lithosphere (the surface of the earth). The atmospheric tidal bulge extends far into space but the tidal bulge of the lithosphere is limited to approximately 12 inches (30 cm) twice a day. The moon, which is approximately 240,000 miles (386,240 km) from the earth, exerts a greater influence on the tides then does the sun, which sits 93 million miles (150 million km) from the earth.

The strength of the sun's gravity is 179 times that of the moon's but the moon is responsible for 56% of the earth's tidal energy while the sun claims responsibility for a mere 44% (due to the moon's proximity but the sun's much larger size). Due to the cyclic rotation of the earth and moon, the tidal cycle is 24 hours and 52 minutes long. During this time, any point on the earth's surface experiences two high tides and two low tides. continue reading below our video 10 Best Universities in the United States The tidal bulge that occurs during high tide in the world ocean follows the revolution of the moon, and the earth rotates eastward through the bulge once every 24 hours and 50 minutes. The water of the entire world ocean is pulled by the moon's gravity. On the opposite side of the earth simultaneously there is a high tide due to the inertia of the ocean water and because the earth is being pulled toward the moon by its gravitational field yet the ocean water remains left behind. This creates a high tide on the side of the earth opposite the high tide caused by the direct pull of the moon.

Points on the sides of the earth between the two tidal bulges experience low tide. The tidal cycle can begin with high tide. For 6 hours and 13 minutes after high tide, the tide recedes in what is known as ebb tide. 6 hours and 13 minutes following high tide is low tide. After low tide, the flood tide begins as the tide rises for the next 6 hours and 13 minutes until high tide occurs and the cycle begins again. Tides are most pronounced along the coastline of the oceans and in bays where tidal range (the difference in height between low tide and high tide) is increased due to the topography and other factors. The Bay of Fundy between Nova Scotia and New Brunswick in Canada experiences the world's greatest tidal range of 50 feet (15.25 meters). This incredible range occurs two times ever 24 hours 52 minutes so every 12 hours and 26 minutes there's a single high tide and a low tide. Northwestern Australia is also home to very high tidal ranges of 35 feet (10.7 meters). Typical coastal tide range is 5 to 10 feet (1.5 to 3 meters).

Large lakes also experience tides but the tidal range is often less than 2 inches (5 cm)! The Bay of Fundy tides are one of 30 locations worldwide where the power of tides can be harnessed to turn turbines to produce electricity. This requires tides greater than 16 feet (5 meters). In areas of higher than usual tides a tidal bore can often can be found. A tidal bore is a wall or wave of water that moves upstream (especially in a river) at the onset of high tide. When the sun, moon, and the earth are lined up, the sun and moon are exerting their strongest force together and tidal ranges are at their maximum. This is known as spring tide (spring tides are not named from the season but from "spring forward") This occurs twice each month, when the moon is full and new. At the first quarter and third quarter moon, the sun and moon are at a 45Â° angle to each other and their gravitational energy is diminished. The lower than normal tidal range that takes place at these times is call neap tides.

Additionally, when the sun and moon are at perigee and are as close to the earth as they get, they exert a greater gravitational influence and produce greater tidal ranges. Alternatively, when the sun and moon as far as they get from the earth, known as apogee, tidal ranges are smaller. The knowledge of the height of tides, both low and high, is vital for many functions, including navigation, fishing, and the construction of coastal facilities.

Question: What is the name of the tides of smallest range, occurring after the moon's first and third quarter?
Answer: NEAP TIDES