document_title: Tide

question_text: when do spring tides on earth take place

question_tokens: when do spring tides on earth take place

root

text: Tide

text: Characteristics

tag: p

text: Tide changes proceed via the following stages:

text:
Sea level rises over several hours, covering the intertidal zone; flood tide.
The water rises to its highest level, reaching high tide.
Sea level falls over several hours, revealing the intertidal zone; ebb tide.
The water stops falling, reaching low tide.

tag: ul

text: Oscillating currents produced by tides are known as tidal streams. The moment that the tidal current ceases is called slack water or slack tide. The tide then reverses direction and is said to be turning. Slack water usually occurs near high water and low water. But there are locations where the moments of slack tide differ significantly from those of high and low water.[5]

text: Tides are commonly semi-diurnal (two high waters and two low waters each day), or diurnal (one tidal cycle per day). The two high waters on a given day are typically not the same height (the daily inequality); these are the higher high water and the lower high water in tide tables. Similarly, the two low waters each day are the higher low water and the lower low water. The daily inequality is not consistent and is generally small when the Moon is over the equator.[6]

text: Definitions

text: From the highest level to the lowest:

text:
Highest astronomical tide (HAT) – The highest tide which can be predicted to occur.  Note that meteorological conditions may add extra height to the HAT.
Mean high water springs (MHWS) – The average of the two high tides on the days of spring tides.
Mean high water neaps (MHWN) – The average of the two high tides on the days of neap tides.
Mean sea level (MSL) – This is the average sea level.  The MSL is constant for any location over a long period.
Mean low water neaps (MLWN) – The average of the two low tides on the days of neap tides.
Mean low water springs (MLWS) – The average of the two low tides on the days of spring tides.
Lowest astronomical tide (LAT) and Chart Datum (CD) – The lowest tide which can be predicted to occur.  Modern charts use this as the chart datum.  Note that under certain meteorological conditions the water may fall lower than this meaning that there is less water than shown on charts.[7]

text: Tidal constituents

text: Tidal constituents are the net result of multiple influences impacting tidal changes over certain periods of time.  Primary constituents include the Earth's rotation, the position of the Moon and Sun relative to the Earth, the Moon's altitude (elevation) above the Earth's equator, and bathymetry.  Variations with periods of less than half a day are called harmonic constituents. Conversely, cycles of days, months, or years are referred to as long period constituents.

text: Tidal forces affect the entire earth, but the movement of solid Earth occurs by mere centimeters.  In contrast, the atmosphere is much more fluid and compressible so its surface moves by kilometers, in the sense of the contour level of a particular low pressure in the outer atmosphere.

text: Principal lunar semi-diurnal constituent

text: In most locations, the largest constituent is the "principal lunar semi-diurnal", also known as the M2 (or M2) tidal constituent. Its period is about 12 hours and 25.2 minutes, exactly half a tidal lunar day, which is the average time separating one lunar zenith from the next, and thus is the time required for the Earth to rotate once relative to the Moon. Simple tide clocks track this constituent. The lunar day is longer than the Earth day because the Moon orbits in the same direction the Earth spins. This is analogous to the minute hand on a watch crossing the hour hand at 12:00 and then again at about 1:05½ (not at 1:00).

text: The Moon orbits the Earth in the same direction as the Earth rotates on its axis, so it takes slightly more than a day—about 24 hours and 50 minutes—for the Moon to return to the same location in the sky. During this time, it has passed overhead (culmination) once and underfoot once (at an hour angle of 00:00 and 12:00 respectively), so in many places the period of strongest tidal forcing is the above-mentioned, about 12 hours and 25 minutes. The moment of highest tide is not necessarily when the Moon is nearest to zenith or nadir, but the period of the forcing still determines the time between high tides.

text: Because the gravitational field created by the Moon weakens with distance from the Moon, it exerts a slightly stronger than average force on the side of the Earth facing the Moon, and a slightly weaker force on the opposite side. The Moon thus tends to "stretch" the Earth slightly along the line connecting the two bodies. The solid Earth deforms a bit, but ocean water, being fluid, is free to move much more in response to the tidal force, particularly horizontally.  As the Earth rotates, the magnitude and direction of the tidal force at any particular point on the Earth's surface change constantly; although the ocean never reaches equilibrium—there is never time for the fluid to "catch up" to the state it would eventually reach if the tidal force were constant—the changing tidal force nonetheless causes rhythmic changes in sea surface height.

text: When there are two high tides each day with different heights (and two low tides also of different heights), the pattern is called a mixed semi-diurnal tide.[8]

text: Range variation: springs and neaps

text: The semi-diurnal range (the difference in height between high and low waters over about half a day) varies in a two-week cycle. Approximately twice a month, around new moon and full moon when the Sun, Moon, and Earth form a line (a configuration known as a syzygy[9]), the tidal force due to the sun reinforces that due to the Moon. The tide's range is then at its maximum; this is called the spring tide. It is not named after the season, but, like that word, derives from the meaning "jump, burst forth, rise", as in a natural spring.

text: When the Moon is at first quarter or third quarter, the Sun and Moon are separated by 90° when viewed from the Earth, and the solar tidal force partially cancels the Moon's tidal force. At these points in the lunar cycle, the tide's range is at its minimum; this is called the neap tide, or neaps.  Neap is an Anglo-Saxon word meaning "without the power", as in forđganges nip (forth-going without-the-power).[10]

text: Spring tides result in high waters that are higher than average, low waters that are lower than average, 'slack water' time that is shorter than average, and stronger tidal currents than average. Neaps result in less-extreme tidal conditions. There is about a seven-day interval between springs and neaps.

text:
Spring tide: Sun and Moon on the same side (0°)

Neap tide: Sun and Moon at 90°

Spring tide: Sun and Moon at opposite sides (180°)

Neap tide: Sun and Moon at 270°

Spring tide: Sun and Moon at the same side (cycle restarts)

text: Lunar altitude

text: The changing distance separating the Moon and Earth also affects tide heights. When the Moon is closest, at perigee, the range increases, and when it is at apogee, the range shrinks. Every 7 1⁄2 lunations (the full cycles from full moon to new to full), perigee coincides with either a new or full moon causing perigean spring tides with the largest tidal range. Even at its most powerful this force is still weak,[11] causing tidal differences of inches at most.[12]

text: Other constituents

text: These include solar gravitational effects, the obliquity (tilt) of the Earth's equator and rotational axis, the inclination of the plane of the lunar orbit and the elliptical shape of the Earth's orbit of the sun.

text: A compound tide (or overtide) results from the shallow-water interaction of its two parent waves.[13]

text: Phase and amplitude

text: Because the M2 tidal constituent dominates in most locations, the stage or phase of a tide, denoted by the time in hours after high water, is a useful concept. Tidal stage is also measured in degrees, with 360° per tidal cycle. Lines of constant tidal phase are called cotidal lines, which are analogous to contour lines of constant altitude on topographical maps. High water is reached simultaneously along the cotidal lines extending from the coast out into the ocean, and cotidal lines (and hence tidal phases) advance along the coast. Semi-diurnal and long phase constituents are measured from high water, diurnal from maximum flood tide. This and the discussion that follows is precisely true only for a single tidal constituent.

text: For an ocean in the shape of a circular basin enclosed by a coastline, the cotidal lines point radially inward and must eventually meet at a common point, the amphidromic point. The amphidromic point is at once cotidal with high and low waters, which is satisfied by zero tidal motion. (The rare exception occurs when the tide encircles an island, as it does around New Zealand, Iceland and Madagascar.) Tidal motion generally lessens moving away from continental coasts, so that crossing the cotidal lines are contours of constant amplitude (half the distance between high and low water) which decrease to zero at the amphidromic point. For a semi-diurnal tide the amphidromic point can be thought of roughly like the center of a clock face, with the hour hand pointing in the direction of the high water cotidal line, which is directly opposite the low water cotidal line. High water rotates about the amphidromic point once every 12 hours in the direction of rising cotidal lines, and away from ebbing cotidal lines. This rotation, caused by the Coriolis effect, is generally clockwise in the southern hemisphere and counterclockwise in the northern hemisphere. The difference of cotidal phase from the phase of a reference tide is the epoch. The reference tide is the hypothetical constituent "equilibrium tide" on a landless Earth measured at 0° longitude, the Greenwich meridian.[16]

text: In the North Atlantic, because the cotidal lines circulate counterclockwise around the amphidromic point, the high tide passes New York Harbor approximately an hour ahead of Norfolk Harbor. South of Cape Hatteras the tidal forces are more complex, and cannot be predicted reliably based on the North Atlantic cotidal lines.

text: Physics

text: History of tidal physics

text: Investigation into tidal physics was important in the early development of heliocentrism[citation needed] and celestial mechanics, with the existence of two daily tides being explained by the Moon's gravity. Later the daily tides were explained more precisely by the interaction of the Moon's and the sun's gravity.

text: Seleucus of Seleucia theorized around 150 B.C. that tides were caused by the Moon.

text: In De temporum ratione (The Reckoning of Time) of 725 Bede linked semidurnal tides and the phenomenon of varying tidal heights to the Moon and its phases.  Bede starts by noting that the tides rise and fall 4/5 of an hour later each day, just as the Moon rises and sets 4/5 of an hour later.[17]  He goes on to emphasise that in two lunar months (59 days) the moon circles the earth 57 times and there are 114 tides.[18]  Bede then observes that the height of a tides varies over the month.  Increasing tides are called malinae and decreasing tides ledones and that the month is divided into  four parts of seven or eight days with alternating malinae and ledones.[19]  In the same passage he also notes the effect of winds to hold back tides.[19]

text: Medieval understanding of the tides was primarily based on works of Muslim astronomers, which became available through Latin translation starting from the 12th century.[20] Abu Ma'shar (d. circa 886), in his Introductorium in astronomiam, taught that ebb and flood tides were caused by the moon.[20] Abu Ma'shar discussed the effects of wind and moon's phases relative to the sun on the tides.[20] In the 12th century, al-Bitruji (d. circa 1204) contributed the notion that the tides were caused by the general circulation of the heavens.[20]

text: Simon Stevin in his 1608 De spiegheling der Ebbenvloet, The theory of ebb and flood, dismissed  a large number of misconceptions that still existed about ebb and flood. Stevin pleaded for the idea that the attraction of the Moon was responsible for the tides and spoke in clear terms about ebb, flood, spring tide and neap tide, stressing that further research needed to be made.[21][22]

text: In 1609 Johannes Kepler also correctly suggested that the gravitation of the Moon caused the tides,[23] which he based upon ancient observations and correlations. It was originally mentioned in Ptolemy's Tetrabiblos[24] as having derived from ancient observation.

text: Galileo Galilei in his 1632 Dialogue Concerning the Two Chief World Systems, whose working title was Dialogue on the Tides, gave an explanation of the tides. The resulting theory, however, was incorrect as he attributed the tides to the sloshing of water caused by the Earth's movement around the sun. He hoped to provide mechanical proof of the Earth's movement. The value of his tidal theory is disputed. Galileo rejected Kepler's explanation of the tides.

text:
Isaac Newton (1642–1727) was the first person to explain tides as the product of the gravitational attraction of astronomical masses. His explanation of the tides (and many other phenomena) was published in the Principia (1687)[25][26] and used his theory of universal gravitation to explain the lunar and solar attractions as the origin of the tide-generating forces.[27]
Newton and others before Pierre-Simon Laplace worked the problem from the perspective of a static system (equilibrium theory), that provided an approximation that described the tides that would occur in a non-inertial ocean evenly covering the whole Earth.[25] The tide-generating force (or its corresponding potential) is still relevant to tidal theory, but as an intermediate quantity (forcing function) rather than as a final result; theory must also consider the Earth's accumulated dynamic tidal response to the applied forces, which response is influenced by ocean depth, the Earth's rotation, and other factors.[28]

text: In 1740, the Académie Royale des Sciences in Paris offered a prize for the best theoretical essay on tides. Daniel Bernoulli, Leonhard Euler, Colin Maclaurin and Antoine Cavalleri shared the prize.[29]

text: Maclaurin used Newton's theory to show that a smooth sphere covered by a sufficiently deep ocean under the tidal force of a single deforming body is a prolate spheroid (essentially a three-dimensional oval) with major axis directed toward the deforming body. Maclaurin was the first to write about the Earth's rotational effects on motion. Euler realized that the tidal force's horizontal component (more than the vertical) drives the tide. In 1744 Jean le Rond d'Alembert studied tidal equations for the atmosphere which did not include rotation.

text: In 1770 James Cook's barque HMS Endeavour grounded on the Great Barrier Reef.  Attempts were made to refloat her on the following tide which failed, but the tide after that lifted her clear with ease.  Whilst she was being repaired in the mouth of the Endeavour River Cook observed the tides over a period of seven weeks.  At neap tides both tides in a day were similar, but at springs the tides rose 7 feet (2.1 m) in the morning but 9 feet (2.7 m) in the evening.[30]

text: Pierre-Simon Laplace formulated a system of partial differential equations relating the ocean's horizontal flow to its surface height, the first major dynamic theory for water tides. The Laplace tidal equations are still in use today. William Thomson, 1st Baron Kelvin, rewrote Laplace's equations in terms of vorticity which allowed for solutions describing tidally driven coastally trapped waves, known as Kelvin waves.[31][32][33]

text: Others including Kelvin and Henri Poincaré further developed Laplace's theory. Based on these developments and the lunar theory of E W Brown describing the motions of the Moon, Arthur Thomas Doodson developed and published in 1921[34] the first modern development of the tide-generating potential in harmonic form: Doodson distinguished 388 tidal frequencies.[35] Some of his methods remain in use.[36]

text: Forces

text:
The tidal force produced by a massive object (Moon, hereafter) on a small particle located on or in an extensive body (Earth, hereafter) is the vector difference between the gravitational force exerted by the Moon on the particle, and the gravitational force that would be exerted on the particle if it were located at the Earth's center of mass.
The solar gravitational force on the Earth is on average 179 times stronger than the lunar, but because the Sun is on average 389 times farther from the Earth, its field gradient is weaker. The solar tidal force is 46% as large as the lunar.[37] More precisely, the lunar tidal acceleration (along the Moon–Earth axis, at the Earth's surface) is about 1.1 × 10−7 g, while the solar tidal acceleration (along the Sun–Earth axis, at the Earth's surface) is about 0.52 × 10−7 g, where g is the gravitational acceleration at the Earth's surface.[38] Venus has the largest effect of the other planets, at 0.000113 times the solar effect.

text: The ocean's surface is closely approximated by an equipotential surface, (ignoring ocean currents) commonly referred to as the geoid. Since the gravitational force is equal to the potential's gradient, there are no tangential forces on such a surface, and the ocean surface is thus in gravitational equilibrium. Now consider the effect of massive external bodies such as the Moon and Sun. These bodies have strong gravitational fields that diminish with distance and act to alter the shape of an equipotential surface on the Earth. This deformation has a fixed spatial orientation relative to the influencing body. The Earth's rotation relative to this shape causes the daily tidal cycle. Gravitational forces follow an inverse-square law (force is inversely proportional to the square of the distance), but tidal forces are inversely proportional to the cube of the distance. The ocean surface moves because of the changing tidal equipotential, rising when the tidal potential is high, which occurs on the parts of the Earth nearest to and furthest from the Moon. When the tidal equipotential changes, the ocean surface is no longer aligned with it, so the apparent direction of the vertical shifts. The surface then experiences a down slope, in the direction that the equipotential has risen.

text: Laplace's tidal equations

text: Ocean depths are much smaller than their horizontal extent. Thus, the response to tidal forcing can be modelled using the Laplace tidal equations which incorporate the following features:

text:
The vertical (or radial) velocity is negligible, and there is no vertical shear—this is a sheet flow.
The forcing is only horizontal (tangential).
The Coriolis effect appears as an inertial force (fictitious) acting laterally to the direction of flow and proportional to velocity.
The surface height's rate of change is proportional to the negative divergence of velocity multiplied by the depth. As the horizontal velocity stretches or compresses the ocean as a sheet, the volume thins or thickens, respectively.

text: The boundary conditions dictate no flow across the coastline and free slip at the bottom.

text: The Coriolis effect (inertial force) steers flows moving towards the equator to the west and flows moving away from the equator toward the east, allowing coastally trapped waves. Finally, a dissipation term can be added which is an analog to viscosity.

text: Amplitude and cycle time

text: The theoretical amplitude of oceanic tides caused by the moon is about 54 centimetres (21 in) at the highest point, which corresponds to the amplitude that would be reached if the ocean possessed a uniform depth, there were no landmasses, and the Earth were rotating in step with the moon's orbit. The sun similarly causes tides, of which the theoretical amplitude is about 25 centimetres (9.8 in) (46% of that of the moon) with a cycle time of 12 hours. At spring tide the two effects add to each other to a theoretical level of 79 centimetres (31 in), while at neap tide the theoretical level is reduced to 29 centimetres (11 in). Since the orbits of the Earth about the sun, and the moon about the Earth, are elliptical, tidal amplitudes change somewhat as a result of the varying Earth–sun and Earth–moon distances. This causes a variation in the tidal force and theoretical amplitude of about ±18% for the moon and ±5% for the sun. If both the sun and moon were at their closest positions and aligned at new moon, the theoretical amplitude would reach 93 centimetres (37 in).

text: Real amplitudes differ considerably, not only because of depth variations and continental obstacles, but also because wave propagation across the ocean has a natural period of the same order of magnitude as the rotation period: if there were no land masses, it would take about 30 hours for a long wavelength surface wave to propagate along the equator halfway around the Earth (by comparison, the Earth's lithosphere has a natural period of about 57 minutes). Earth tides, which raise and lower the bottom of the ocean, and the tide's own gravitational self attraction are both significant and further complicate the ocean's response to tidal forces.

text: Dissipation

text:
Earth's tidal oscillations introduce dissipation at an average rate of about 3.75 terawatts.[39]
About 98% of this dissipation is by marine tidal movement.[40]
Dissipation arises as basin-scale tidal flows drive smaller-scale flows which experience turbulent dissipation. This tidal drag creates torque on the moon that gradually transfers angular momentum to its orbit, and a gradual increase in Earth–moon separation. The equal and opposite torque on the Earth correspondingly decreases its rotational velocity. Thus, over geologic time, the moon recedes from the Earth, at about 3.8 centimetres (1.5 in)/year, lengthening the terrestrial day.[41]
Day length has increased by about 2 hours in the last 600 million years. Assuming (as a crude approximation) that the deceleration rate has been constant, this would imply that 70 million years ago, day length was on the order of 1% shorter with about 4 more days per year.

text: Bathymetry

text: The shape of the shoreline and the ocean floor changes the way that tides propagate, so there is no simple, general rule that predicts the time of high water from the Moon's position in the sky. Coastal characteristics such as underwater bathymetry and coastline shape mean that individual location characteristics affect tide forecasting; actual high water time and height may differ from model predictions due to the coastal morphology's effects on tidal flow. However, for a given location the relationship between lunar altitude and the time of high or low tide (the lunitidal interval) is relatively constant and predictable, as is the time of high or low tide relative to other points on the same coast. For example, the high tide at Norfolk, Virginia, U.S., predictably occurs approximately two and a half hours before the Moon passes directly overhead.

text: Land masses and ocean basins act as barriers against water moving freely around the globe, and their varied shapes and sizes affect the size of tidal frequencies. As a result, tidal patterns vary. For example, in the U.S., the East coast has predominantly semi-diurnal tides, as do Europe's Atlantic coasts, while the West coast predominantly has mixed tides.[42][43][44]

text: Observation and prediction

text: History

text: From ancient times, tidal observation and discussion has increased in  sophistication, first marking the daily recurrence, then tides' relationship to the sun and moon. Pytheas travelled to the British Isles about 325 BC and seems to be the first to have related spring tides to the phase of the moon.

text: In the 2nd century BC, the Babylonian astronomer, Seleucus of Seleucia, correctly described the phenomenon of tides in order to support his heliocentric theory.[45] He correctly theorized that tides were caused by the moon, although he believed that the interaction was mediated by the pneuma. He noted that tides varied in time and strength in different parts of the world. According to Strabo (1.1.9), Seleucus was the first to link tides to the lunar attraction, and that the height of the tides depends on the moon's position relative to the sun.[46]

text: The Naturalis Historia of Pliny the Elder collates many tidal observations, e.g., the spring tides are a few days after (or before) new and full moon and are highest around the equinoxes, though Pliny noted many relationships now regarded as fanciful. In his Geography, Strabo described tides in the Persian Gulf having their greatest range when the moon was furthest from the plane of the equator. All this despite the relatively small amplitude of Mediterranean basin tides. (The strong currents through the Euripus Strait and the Strait of Messina puzzled Aristotle.) Philostratus discussed tides in Book Five of The Life of Apollonius of Tyana. Philostratus mentions the moon, but attributes tides to "spirits". In Europe around 730 AD, the Venerable Bede described how the rising tide on one coast of the British Isles coincided with the fall on the other and described the time progression of high water along the Northumbrian coast.

text: The first tide table in China was recorded in 1056 AD primarily for visitors wishing to see the famous tidal bore in the Qiantang River. The first known British tide table is thought to be that of John Wallingford, who died Abbot of St. Albans in 1213, based on high water occurring 48 minutes later each day, and three hours earlier at the Thames mouth than upriver at London.[47]

text: William Thomson (Lord Kelvin) led the first systematic harmonic analysis of tidal records starting in 1867. The main result was the building of a tide-predicting machine using a system of pulleys to add together six harmonic time functions. It was "programmed" by resetting gears and chains to adjust phasing and amplitudes. Similar machines were used until the 1960s.[48]

text: The first known sea-level record of an entire spring–neap cycle was made in 1831 on the Navy Dock in the Thames Estuary. Many large ports had automatic tide gauge stations by 1850.

text: William Whewell first mapped co-tidal lines ending with a nearly global chart in 1836. In order to make these maps consistent, he hypothesized the existence of amphidromes where co-tidal lines meet in the mid-ocean. These points of no tide were confirmed by measurement in 1840 by Captain Hewett, RN, from careful soundings in the North Sea.[31]

text: Timing

text: The tidal forces due to the Moon and Sun generate very long  waves which travel all around the ocean following the paths shown in co-tidal charts. The time when the crest of the wave reaches a port then gives the time of high water at the port. The time taken for the wave to travel around the ocean also means that there is a delay between the phases of the moon and their effect on the tide. Springs and neaps in the North Sea, for example, are two days behind the new/full moon and first/third quarter moon. This is called the tide's age.[49][50]

text:
The ocean bathymetry greatly influences the tide's exact time and height at a particular coastal point. There are some extreme cases; the Bay of Fundy, on the east coast of Canada, is often stated to have the world's highest tides because of its shape, bathymetry, and its distance from the continental shelf edge.[51] Measurements made in November 1998 at Burntcoat Head in the Bay of Fundy recorded a maximum range of 16.3 metres (53 ft) and a highest predicted extreme of 17 metres (56 ft).[52][53]
Similar measurements made in March 2002 at Leaf Basin, Ungava Bay in northern Quebec gave similar values (allowing for measurement errors), a maximum range of 16.2 metres (53 ft) and a highest predicted extreme of 16.8 metres (55 ft).[52][53]  Ungava Bay and the Bay of Fundy lie similar distances from the continental shelf edge, but Ungava Bay is free of pack ice for about four months every year while the Bay of Fundy rarely freezes.

text: Southampton in the United Kingdom has a double high water caused by the interaction between the M2 and M4 tidal constituents.[54] Portland has double low waters for the same reason.  The M4 tide is found all along the south coast of the United Kingdom, but its effect is most noticeable between the Isle of Wight and Portland because the M2 tide is lowest in this region.

text: Because the oscillation modes of the Mediterranean Sea and the Baltic Sea do not coincide with any significant astronomical forcing period, the largest tides are close to their narrow connections with the Atlantic Ocean. Extremely small tides also occur for the same reason in the Gulf of Mexico and Sea of Japan. Elsewhere, as along the southern coast of Australia, low tides can be due to the presence of a nearby amphidrome.

text: Analysis

text: Isaac Newton's theory of gravitation first enabled an explanation of why there were generally two tides a day, not one, and offered hope for a detailed understanding of tidal forces and behavior. Although it may seem that tides could be predicted via a sufficiently detailed knowledge of instantaneous astronomical forcings, the actual tide at a given location is determined by astronomical forces accumulated over many days. In addition, precise results require detailed knowledge of the shape of all the ocean basins—their bathymetry, and coastline shape.

text: Current procedure for analysing tides follows the method of harmonic analysis introduced in the 1860s by William Thomson. It is based on the principle that the astronomical theories of the motions of sun and moon determine a large number of component frequencies, and at each frequency there is a component of force tending to produce tidal motion, but that at each place of interest on the Earth, the tides respond at each frequency with an amplitude and phase peculiar to that locality.  At each place of interest, the tide heights are therefore measured for a period of time sufficiently long (usually more than a year in the case of a new port not previously studied) to enable the response at each significant tide-generating frequency to be distinguished by analysis, and to extract the tidal constants for a sufficient number of the strongest known components of the astronomical tidal forces to enable practical tide prediction. The tide heights are expected to follow the tidal force, with a constant amplitude and phase delay for each component.  Because astronomical frequencies and phases can be calculated with certainty, the tide height at other times can then be predicted once the response to the harmonic components of the astronomical tide-generating forces has been found.

text: The main patterns in the tides are

text:
the twice-daily variation
the difference between the first and second tide of a day
the spring–neap cycle
the annual variation

text: The Highest Astronomical Tide is the perigean spring tide when both the sun and moon are closest to the Earth.

text: When confronted by a periodically varying function, the standard approach is to employ Fourier series, a form of analysis that uses sinusoidal functions as a basis set, having frequencies that are zero, one, two, three, etc. times the frequency of a particular fundamental cycle. These multiples are called harmonics of the fundamental frequency, and the process is termed harmonic analysis. If the basis set of sinusoidal functions suit the behaviour being modelled, relatively few harmonic terms need to be added. Orbital paths are very nearly circular, so sinusoidal variations are suitable for tides.

text: For the analysis of tide heights, the Fourier series approach has in practice to be made more elaborate than the use of a single frequency and its harmonics.  The tidal patterns are decomposed into many sinusoids having many fundamental frequencies, corresponding (as in the lunar theory) to many different combinations of the motions of the Earth, the moon, and the angles that define the shape and location of their orbits.

text: For tides, then, harmonic analysis is not limited to harmonics of a single frequency.[55] In other words, the harmonies are multiples of many fundamental frequencies, not just of the fundamental frequency of the simpler Fourier series approach.  Their representation as a Fourier series having only one fundamental frequency and its (integer) multiples would require many terms, and would be severely limited in the time-range for which it would be valid.

text: The study of tide height by harmonic analysis was begun by Laplace, William Thomson (Lord Kelvin), and George Darwin. A.T. Doodson extended their work, introducing the Doodson Number notation to organise the hundreds of resulting terms. This approach has been the international standard ever since, and the complications arise as follows: the tide-raising force is notionally given by sums of several terms. Each term is of the form

text: where A is the amplitude, ω is the angular frequency usually given in degrees per hour corresponding to t measured in hours, and p is the phase offset with regard to the astronomical state at time t = 0 . There is one term for the moon and a second term for the sun. The phase p of the first harmonic for the moon term is called the lunitidal interval or high water interval. The next step is to accommodate the harmonic terms due to the elliptical shape of the orbits. Accordingly, the value of A is not a constant but also varying with time, slightly, about some average figure. Replace it then by A(t) where A is another sinusoid, similar to the cycles and epicycles of Ptolemaic theory. Accordingly,

text: which is to say an average value A with a sinusoidal variation about it of magnitude Aa, with frequency ωa and phase pa. Thus the simple term is now the product of two cosine factors:

text: Given that for any x and y

text:
it is clear that a compound term involving the product of two cosine terms each with their own frequency is the same as three simple cosine terms that are to be added at the original frequency and also at frequencies which are the sum and difference of the two frequencies of the product term. (Three, not two terms, since the whole expression is

(
1
+
cos

x
)
cos

y

{\displaystyle (1+\cos x)\cos y}

.) Consider further that the tidal force on a location depends also on whether the moon (or the sun) is above or below the plane of the equator, and that these attributes have their own periods also incommensurable with a day and a month, and it is clear that many combinations result. With a careful choice of the basic astronomical frequencies, the Doodson Number annotates the particular additions and differences to form the frequency of each simple cosine term.

text: Remember that astronomical tides do not include weather effects. Also, changes to local conditions (sandbank movement, dredging harbour mouths, etc.) away from those prevailing at the measurement time affect the tide's actual timing and magnitude. Organisations quoting a "highest astronomical tide" for some location may exaggerate the figure as a safety factor against analytical uncertainties, distance from the nearest measurement point, changes since the last observation time, ground subsidence, etc., to avert liability should an engineering work be overtopped. Special care is needed when assessing the size of a "weather surge" by subtracting the astronomical tide from the observed tide.

text: Careful Fourier data analysis over a nineteen-year period (the National Tidal Datum Epoch in the U.S.) uses frequencies called the tidal harmonic constituents. Nineteen years is preferred because the Earth, moon and sun's relative positions repeat almost exactly in the Metonic cycle of 19 years, which is long enough to include the 18.613 year lunar nodal tidal constituent. This analysis can be done using only the knowledge of the forcing period, but without detailed understanding of the mathematical derivation, which means that useful tidal tables have been constructed for centuries.[56] The resulting amplitudes and phases can then be used to predict the expected tides. These are usually dominated by the constituents near 12 hours (the semi-diurnal constituents), but there are major constituents near 24 hours (diurnal) as well. Longer term constituents are 14 day or fortnightly, monthly, and semiannual. Semi-diurnal tides dominated coastline, but some areas such as the South China Sea and the Gulf of Mexico are primarily diurnal. In the semi-diurnal areas, the primary constituents M2 (lunar) and S2 (solar) periods differ slightly, so that the relative phases, and thus the amplitude of the combined tide, change fortnightly (14 day period).[57]

text: In the M2 plot above, each cotidal line differs by one hour from its neighbors, and the thicker lines show tides in phase with equilibrium at Greenwich. The lines rotate around the amphidromic points counterclockwise in the northern hemisphere so that from Baja California Peninsula to Alaska and from France to Ireland the M2 tide propagates northward. In the southern hemisphere this direction is clockwise. On the other hand, M2 tide propagates counterclockwise around New Zealand, but this is because the islands act as a dam and permit the tides to have different heights on the islands' opposite sides. (The tides do propagate northward on the east side and southward on the west coast, as predicted by theory.)

text: The exception is at Cook Strait where the tidal currents periodically link high to low water. This is because cotidal lines 180° around the amphidromes are in opposite phase, for example high water across from low water at each end of Cook Strait. Each tidal constituent has a different pattern of amplitudes, phases, and amphidromic points, so the M2 patterns cannot be used for other tide components.

text: Example calculation

text: Because the moon is moving in its orbit around the earth and in the same sense as the Earth's rotation, a point on the earth must rotate slightly further to catch up so that the time between semidiurnal tides is not twelve but 12.4206 hours—a bit over twenty-five minutes extra. The two peaks are not equal. The two high tides a day alternate in maximum heights: lower high (just under three feet), higher high (just over three feet), and again lower high. Likewise for the low tides.

text: When the Earth, moon, and sun are in line (sun–Earth–moon, or sun–moon–Earth) the two main influences combine to produce spring tides; when the two forces are opposing each other as when the angle moon–Earth–sun is close to ninety degrees, neap tides result. As the moon moves around its orbit it changes from north of the equator to south of the equator. The alternation in high tide heights becomes smaller, until they are the same (at the lunar equinox, the moon is above the equator), then redevelop but with the other polarity, waxing to a maximum difference and then waning again.

text: Current

text: The tides' influence on current flow is much more difficult to analyse, and data is much more difficult to collect. A tidal height is a simple number which applies to a wide region simultaneously. A flow has both a magnitude and a direction, both of which can vary substantially with depth and over short distances due to local bathymetry. Also, although a water channel's center is the most useful measuring site, mariners object when current-measuring equipment obstructs waterways. A flow proceeding up a curved channel is the same flow, even though its direction varies continuously along the channel. Surprisingly, flood and ebb flows are often not in opposite directions. Flow direction is determined by the upstream channel's shape, not the downstream channel's shape. Likewise, eddies may form in only one flow direction.

text: Nevertheless, current analysis is similar to tidal analysis: in the simple case, at a given location the flood flow is in mostly one direction, and the ebb flow in another direction. Flood velocities are given positive sign, and ebb velocities negative sign. Analysis proceeds as though these are tide heights.

text: In more complex situations, the main ebb and flood flows do not dominate. Instead, the flow direction and magnitude trace an ellipse over a tidal cycle (on a polar plot) instead of along the ebb and flood lines. In this case, analysis might proceed along pairs of directions, with the primary and secondary directions at right angles. An alternative is to treat the tidal flows as complex numbers, as each value has both a magnitude and a direction.

text: Tide flow information is most commonly seen on nautical charts, presented as a table of flow speeds and bearings at hourly intervals, with separate tables for spring and neap tides. The timing is relative to high water at some harbour where the tidal behaviour is similar in pattern, though it may be far away.

text: As with tide height predictions, tide flow predictions based only on astronomical factors do not incorporate weather conditions, which can completely change the outcome.

text: The tidal flow through Cook Strait between the two main islands of New Zealand is particularly interesting, as the tides on each side of the strait are almost exactly out of phase, so that one side's high water is simultaneous with the other's low water. Strong currents result, with almost zero tidal height change in the strait's center. Yet, although the tidal surge normally flows in one direction for six hours and in the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions, the reverse surge might be entirely overcome so that the flow continues in the same direction through three or more surge periods.

text: A further complication for Cook Strait's flow pattern is that the tide at the north side (e.g. at Nelson) follows the common bi-weekly spring–neap tide cycle (as found along the west side of the country), but the south side's tidal pattern has only one cycle per month, as on the east side: Wellington, and Napier.

text: The graph of Cook Strait's tides shows separately the high water and low water height and time, through November 2007; these are not measured values but instead are calculated from tidal parameters derived from years-old measurements. Cook Strait's nautical chart offers tidal current information. For instance the January 1979 edition for 41°13·9’S 174°29·6’E (north west of Cape Terawhiti) refers timings to Westport while the January 2004 issue refers to Wellington. Near Cape Terawhiti in the middle of Cook Strait the tidal height variation is almost nil while the tidal current reaches its maximum, especially near the notorious Karori Rip. Aside from weather effects, the actual currents through Cook Strait are influenced by the tidal height differences between the two ends of the strait and as can be seen, only one of the two spring tides at the north end (Nelson) has a counterpart spring tide at the south end (Wellington), so the resulting behaviour follows neither reference harbour.[citation needed]

text: Power generation

text: Tidal energy can be extracted by two means: inserting a water turbine into a tidal current, or building ponds that release/admit water through a turbine. In the first case, the energy amount is entirely determined by the timing and tidal current magnitude. However, the best currents may be unavailable because the turbines would obstruct ships. In the second, the impoundment dams are expensive to construct, natural water cycles are completely disrupted, ship navigation is disrupted. However, with multiple ponds, power can be generated at chosen times. So far, there are few installed systems for tidal power generation (most famously, La Rance at Saint Malo, France) which face many difficulties. Aside from environmental issues, simply withstanding corrosion and biological fouling pose engineering challenges.

text: Tidal power proponents point out that, unlike wind power systems, generation levels can be reliably predicted, save for weather effects. While some generation is possible for most of the tidal cycle, in practice turbines lose efficiency at lower operating rates. Since the power available from a flow is proportional to the cube of the flow speed, the times during which high power generation is possible are brief.

text: Navigation

text: Tidal flows are important for navigation, and significant errors in position occur if they are not accommodated. Tidal heights are also important; for example many rivers and harbours have a shallow "bar" at the entrance which prevents boats with significant draft from entering at low tide.

text: Until the advent of automated navigation, competence in calculating tidal effects was important to naval officers. The certificate of examination for lieutenants in the Royal Navy once declared that the prospective officer was able to "shift his tides".[58]

text: Tidal flow timings and velocities appear in tide charts or a tidal stream atlas. Tide charts come in sets. Each chart covers a single hour between one high water and another (they ignore the leftover 24 minutes) and show the average tidal flow for that hour. An arrow on the tidal chart indicates the direction and the average flow speed (usually in knots) for spring and neap tides. If a tide chart is not available, most nautical charts have "tidal diamonds" which relate specific points on the chart to a table giving tidal flow direction and speed.

text: The standard procedure to counteract tidal effects on navigation is to (1) calculate a "dead reckoning" position (or DR) from travel distance and direction, (2) mark the chart (with a vertical cross like a plus sign) and (3) draw a line from the DR in the tide's direction. The distance the tide moves the boat along this line is computed by the tidal speed, and this gives an "estimated position" or EP (traditionally marked with a dot in a triangle).

text: Nautical charts display the water's "charted depth" at specific locations with "soundings" and the use of bathymetric contour lines to depict the submerged surface's shape. These depths are relative to a "chart datum", which is typically the water level at the lowest possible astronomical tide (although other datums are commonly used, especially historically, and tides may be lower or higher for meteorological reasons) and are therefore the minimum possible water depth during the tidal cycle. "Drying heights" may also be shown on the chart, which are the heights of the exposed seabed at the lowest astronomical tide.

text: Tide tables list each day's high and low water heights and times. To calculate the actual water depth, add the charted depth to the published tide height. Depth for other times can be derived from tidal curves published for major ports. The rule of twelfths can suffice if an accurate curve is not available. This approximation presumes that the increase in depth in the six hours between low and high water is: first hour — 1/12, second — 2/12, third — 3/12, fourth — 3/12, fifth — 2/12, sixth — 1/12.

text: Biological aspects

text: Intertidal ecology

text: Intertidal ecology is the study of ecosystems between the low- and high-water lines along a shore. At low water, the intertidal zone is exposed (or emersed), whereas at high water, it is underwater (or immersed). Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as among the different species. The most important interactions may vary according to the type of intertidal community. The broadest classifications are based on substrates — rocky shore or soft bottom.

text: Intertidal organisms experience a highly variable and often hostile environment, and have adapted to cope with and even exploit these conditions. One easily visible feature is vertical zonation, in which the community divides into distinct horizontal bands of specific species at each elevation above low water. A species' ability to cope with desiccation determines its upper limit, while competition with other species sets its lower limit.

text: Humans use intertidal regions for food and recreation. Overexploitation can damage intertidals directly. Other anthropogenic actions such as introducing invasive species and climate change have large negative effects. Marine Protected Areas are one option communities can apply to protect these areas and aid scientific research.

text: Biological rhythms

text: The approximately fortnightly tidal cycle has large effects on intertidal[59] and marine organisms.[60] Hence their biological rhythms tend to occur in rough multiples of this period. Many other animals such as the vertebrates, display similar rhythms. Examples include gestation and egg hatching. In humans, the menstrual cycle lasts roughly a lunar month, an even multiple of the tidal period. Such parallels at least hint at the common descent of all animals from a marine ancestor.[61]

text: Other tides

text: When oscillating tidal currents in the stratified ocean flow over uneven bottom topography, they generate internal waves with tidal frequencies. Such waves are called internal tides.

text: Shallow areas in otherwise open water can experience rotary tidal currents, flowing in directions that continually change and thus the flow direction (not the flow) completes a full rotation in 12 1⁄2 hours (for example, the Nantucket Shoals).[62]

text: In addition to oceanic tides, large lakes can experience small tides and even planets can experience atmospheric tides and Earth tides. These are continuum mechanical phenomena. The first two take place in fluids. The third affects the Earth's thin solid crust surrounding its semi-liquid interior (with various modifications).

text: Lake tides

text:
Large lakes such as Superior and Erie can experience tides of 1 to 4 cm (0.39 to 1.6 in), but these can be masked by meteorologically induced phenomena such as seiche.[63] The tide in Lake Michigan is described as 0.5 to 1.5 inches (13 to 38 mm)[64] or 1 3⁄4 inches.[65]
This is so small that other larger effects completely mask any tide, and as such these lakes are considered non-tidal.[66]

text: Atmospheric tides

text: Atmospheric tides are negligible at ground level and aviation altitudes, masked by weather's much more important effects. Atmospheric tides are both gravitational and thermal in origin and are the dominant dynamics from about 80 to 120 kilometres (50 to 75 mi), above which the molecular density becomes too low to support fluid behavior.

text: Earth tides

text: Earth tides or terrestrial tides affect the entire Earth's mass, which acts similarly to a liquid gyroscope with a very thin crust. The Earth's crust shifts (in/out, east/west, north/south) in response to lunar and solar gravitation, ocean tides, and atmospheric loading. While negligible for most human activities, terrestrial tides' semi-diurnal amplitude can reach about 55 centimetres (22 in) at the equator—15 centimetres (5.9 in) due to the sun—which is important in GPS calibration and VLBI measurements. Precise astronomical angular measurements require knowledge of the Earth's rotation rate and polar motion, both of which are influenced by Earth tides. The semi-diurnal M2 Earth tides are nearly in phase with the moon with a lag of about two hours.[citation needed]

text: Galactic tides

text: Galactic tides are the tidal forces exerted by galaxies on stars within them and satellite galaxies orbiting them. The galactic tide's effects on the Solar System's Oort cloud are believed to cause 90 percent of long-period comets.[67]

text: Misnomers

text: Tsunamis, the large waves that occur after earthquakes, are sometimes called tidal waves, but this name is given by their resemblance to the tide, rather than any actual link to the tide. Other phenomena unrelated to tides but using the word tide are rip tide, storm tide, hurricane tide, and black or red tides.  Many of these usages are historic and refer to the earlier meaning of tide as "a portion of time, a season".[68]


document_title: Medieval technology

question_text: what was one of the weapon technologies that emerged during the crusades

question_tokens: what was one of the weapon technologies that emerged during the crusades

text: Medieval technology

text: Civil technologies[edit]

text: The following is a list of some important medieval technologies. The approximate date or first mention of a technology in medieval Europe is given. Technologies were often a matter of cultural exchange and date and place of first inventions are not listed here (see main links for a more complete history of each).

text: Agriculture[edit]

text: Carruca (6th to 9th centuries)

text: A type of heavy wheeled plough commonly found in Northern Europe.[4] The device consisted of four major parts. The first part was a Coulter (agriculture) at the bottom of the plough.[5] This knife was used to vertically cut into the top sod to allow for the plowshare to work.[5] The plowshare was the second pair of knives which cut the sod horizontally, detaching it from the ground below.[5] The third part was the moldboard, which curled the sod outward.[5] The fourth part of the device was the team of eight oxen guided by the farmer.[6] This type of plough eliminated the need for cross-plowing by turning over the furrow instead of merely pushing it outward.[6] This type of wheeled plough made seed placement more consistent throughout the farm as the blade could be locked in at a certain level relative to the wheels.[7] A disadvantage to this type of plough was its maneuverability.[7] Since this equipment was large and lead by a small herd of oxen, turning the plough was difficult and time-consuming.[7] This caused many farmers to turn away from traditional square fields and adopt a longer, more rectangular field to ensure maximum efficiency.[7]

text: Ard (plough) (5th century)

text: An early medieval plough that consisted of a sharpened wooden post pulled by either animals or humans.[8] This lightweight and primitive plough was used primarily before the invention of the carruca.[8] The ard was inefficient in more firm northern soil but did decent work in southern areas where the soil was much softer.[8] Although the ard required the user to apply constant pressure to the plough in order to make sure the edge could break the ground, the soil was merely pushed to the sides instead of being properly turned over.[8]

text: Horse collar (6th to 9th centuries)

text: Once oxen started to be replaced by horses on farms and in fields, the yoke became obsolete due to its shape not working well with a horses' posture.[9] The first design for a horse collar was a throat-and-girth-harness.[9] These types of harnesses were unreliable though due to them not being sufficiently set in place.[9] The loose straps were prone to slipping and shifting positions as the horse was working and often caused asphyxiation.[9] Around the eighth century, the introduction of the rigid collar eliminated the problem of choking.[9] The rigid collar was "placed over the horses head and rested on its shoulders.[9] This permitted unobstructed breathing and placed the weight of the plow or wagon where the horse could best support it."[9]

text: Horseshoes (9th century)

text: Allowed horses to carry larger loads and move around with greater traction on hard to walk surfaces.[10] The practice of shoeing horses was initially practiced in the Roman Empire but lost popularity throughout the Middle Ages until around the 11th century.[10] Although horses in the southern lands could easily work while on the softer soil, the rocky soil of the north proved to be damaging to the horses' hooves.[11] Since the north was the problematic area, this is where shoeing horses first became popular.[11] The introduction of gravel roadways was also cause for the popularity of horseshoeing.[11] The loads a shoed horse could take on these roads were significantly higher than one that was barefoot.[11] By the 14th century, not only did horses have shoes, but many farmers were shoeing oxen and donkeys in order to help prolong the life of their hooves.[11] The size and weight of the horseshoe changed significantly over the course of the middle ages.[11] In the 10th century, horseshoes were secured by six nails and weighed around one-quarter of a pound, but throughout the years, the shoes grew larger and by the 14th century, the shoes were being secured with eight nails and weighed nearly half a pound.[11]

text: Crop rotation (8th century)

text: Also called the Two-field system. This system included the farmers' field being divided into two separate crops.[12] One field would grow a crop while the other was left to grow and was used to feed livestock and regain lost nutrients.[12] Every year, the two fields would switch in order to ensure fields did not become nutrient deficient.[12] In the 11th century, this system was introduced into Sweden and spread to become the most popular form of farming.[12]

text: Three-field system (8th century)

text: The ideal three-field system is one that separates a section of land into three equal parts.[13] Each one of the three parts holds a different crop.[13] One part holds a spring crop, such as barley or oats, another part holds a winter crop, such as wheat or rye, and the third part is an off-field that is left alone to grow and is used to help feed livestock.[13] By rotating the three crops to a new part of the land after each year, the off-field regains some of the nutrients lost during the growing of the two crops.[13] This system increases agricultural productivity over the Two-field system by only having one-third of the field not being used instead of one half.[13] Another advantage of crop rotation is that many scholars believe it helped increase yields by up to 50%.[13]

text: Wine press (12th century)

text: This device was the first practical means of Pressing (wine) on a plane surface.[14] The wine press was an expensive piece of machinery that only the wealthy could afford.[14] The method of Grape stomping was often used as a less expensive alternative.[14] While white wines required the use of a wine press in order to preserve the color of the wine by removing the juices quickly from the skin, red wine did not need to be pressed until the end of the juice removal process since the color did not matter.[14] Many red wine winemakers used their feet to smash the grapes then used a press to remove any juice that remained in the grape skins.[14]

text: Qanat (5th century)

text: An underground passage used to water fields, crops, and provide drinking water.[15] These tunnels had a gradual slope which used gravity to pull the water from either an aquifer or water well.[15] This system was originally found in middle eastern areas and is still used today in places where surface water is hard to find.

text: Architecture and construction[edit]

text: Artesian well (1126)

text: A thin rod with a hard iron cutting edge is placed in the bore hole and repeatedly struck with a hammer, underground water pressure forces the water up the hole without pumping. Artesian wells are named after the town of Artois in France, where the first one was drilled by Carthusian monks in 1126.

text: Central heating through underfloor channels (9th century)

text: In the early medieval Alpine upland, a simpler central heating system where heat travelled through underfloor channels from the furnace room replaced the Roman hypocaust at some places. In Reichenau Abbey a network of interconnected underfloor channels heated the 300 m2 large assembly room of the monks during the winter months. The degree of efficiency of the system has been calculated at 90%.[16]

text: Rib vault (12th century)

text: An essential element for the rise of Gothic architecture, rib vaults allowed vaults to be built for the first time over rectangles of unequal lengths. It also greatly facilitated scaffolding and largely replaced the older groin vault.

text: Chimney (12th century)

text: The earliest true chimneys appeared in Northern Europe during the 12th century, and with them came the first true fireplaces.

text: Segmental arch bridge (1345)

text: The Ponte Vecchio in Florence is considered medieval Europe's first stone segmental arch bridge.

text: Treadwheel crane (1220s)

text: The earliest reference to a treadwheel in archival literature is in France about 1225,[17] followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240.[18] Apart from tread-drums, windlasses and occasionally cranks were employed for powering cranes.[19]

text: Stationary harbour crane (1244)

text: Stationary harbour cranes are considered a new development of the Middle Ages; its earliest use being documented for Utrecht in 1244.[20] The typical harbour crane was a pivoting structure equipped with double treadwheels. There were two types: wooden gantry cranes pivoting on a central vertical axle and stone tower cranes which housed the windlass and treadwheels with only the jib arm and roof rotating.[1] These cranes were placed on docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.[20] Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340.[21]

text: Floating crane

text: Beside the stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century.[1]

text: Mast crane

text: Some harbour cranes were specialised at mounting masts to newly built sailing ships, such as in Gdańsk, Cologne and Bremen.[1]

text: Wheelbarrow (1170s)

text: The wheelbarrow proved useful in building construction, mining operations, and agriculture. Literary evidence for the use of wheelbarrows appeared between 1170 and 1250 in north-western Europe. The first depiction is in a drawing by Matthew Paris in the mid-13th century.

text: Art[edit]

text: Oil paint (by 1125)

text: As early as the 13th century, oil was used to add details to tempera paintings and paint wooden statues. Flemish painter Jan van Eyck developed the use of a stable oil mixture for panel painting around 1410.[22]

text: Clocks[edit]

text: Hourglass (1338)

text: Reasonably dependable, affordable and accurate measure of time. Unlike water in a clepsydra, the rate of flow of sand is independent of the depth in the upper reservoir, and the instrument is not liable to freeze. Hourglasses are a medieval innovation (first documented in Siena, Italy).

text: Mechanical clocks (13th to 14th centuries)

text: A European innovation, these weight-driven clocks were used primarily in clock towers.

text: Mechanics[edit]

text: Compound crank

text: The Italian physician Guido da Vigevano combines in his 1335 Texaurus, a collection of war machines intended for the recapture of the Holy Land, two simple cranks to form a compound crank for manually powering war carriages and paddle wheel boats. The devices were fitted directly to the vehicle's axle respectively to the shafts turning the paddle wheels.[23]

text: Metallurgy[edit]

text: Blast furnace (1150–1350)

text: European cast iron first appears in Middle Europe (for instance Lapphyttan in Sweden, Dürstel in Switzerland and the Märkische Sauerland in Germany) around 1150,[24] in some places according to recent research even before 1100.[25] The technique is considered to be an independent European development.[26]

text: Milling[edit]

text: Paper mill (13th century)

text: The first certain use of a water-powered paper mill, evidence for which is elusive in both Chinese[27][28] and Muslim paper making,[29] dates to 1282.[30]

text: Rolling mill (15th century)

text: Used to produce metal sheet of an even thickness. First used on soft, malleable metals, such as lead, gold and tin. Leonardo da Vinci described a rolling mill for wrought iron.

text: Tidal Mills (6th century)

text: The earliest tidal mills were excavated on the Irish coast where watermillers knew and employed the two main waterwheel types: a 6th-century tide mill at Killoteran near Waterford was powered by a vertical waterwheel,[31] while the tide changes at Little Island were exploited by a twin-flume horizontal-wheeled mill (c. 630) and a vertical undershot waterwheel alongside it.[32][33] Another early example is the Nendrum Monastery mill from 787 which is estimated to have developed seven to eight horsepower at its peak.[34][35]

text: Vertical windmills (1180s)

text: Invented in Europe as the pivotable post mill, the first surviving mention of one comes from Yorkshire in England in 1185. They were efficient at grinding grain or draining water. Stationary tower mills were also developed in the 13th century.

text: Water hammer (12th century at the latest)

text: Used in metallurgy to forge the metal blooms from bloomeries and Catalan forges, they replaced manual hammerwork. The water hammer was eventually superseded by steam hammers in the 19th century.

text: Navigation[edit]

text: Dry compass (12th century)

text: The first European mention of the directional compass is in Alexander Neckam's On the Natures of Things, written in Paris around 1190.[36] It was either transmitted from China or the Arabs or an independent European innovation. Dry compass were invented in the Mediterranean around 1300.[37]

text: Astronomical compass (1269)

text: The French scholar Pierre de Maricourt describes in his experimental study Epistola de magnete (1269) three different compass designs he has devised for the purpose of astronomical observation.[38]

text: Stern-mounted rudders (1180s)

text: The first depiction of a pintle-and-gudgeon rudder on church carvings dates to around 1180. They first appeared with cogs in the North and Baltic Seas and quickly spread to Mediterranean. The iron hinge system was the first stern rudder permanently attached to the ship hull and made a vital contribution to the navigation achievements of the age of discovery and thereafter.[39]

text: Printing, paper and reading[edit]

text: Movable type printing press (1440s)

text: Johannes Gutenberg's great innovation was not the printing itself, but instead of using carved plates as in woodblock printing, he used separate letters (types) from which the printing plates for pages were made up. This meant the types were recyclable and a page cast could be made up far faster.

text: Paper (13th century)

text: Paper was invented in China and transmitted through Islamic Spain in the 13th century. In Europe, the paper-making processes was mechanized by water-powered mills and paper presses (see paper mill).

text: Rotating bookmark (13th century)

text: A rotating disc and string device used to mark the page, column, and precise level in the text where a person left off reading in a text. Materials used were often leather, velum, or paper.

text: Spectacles (1280s)

text: The first spectacles, invented in Florence, used convex lenses which were of help only to the far-sighted. Concave lenses were not developed prior to the 15th century.

text: Watermark (1282)

text: This medieval innovation was used to mark paper products and to discourage counterfeiting. It was first introduced in Bologna, Italy.

text: Science and learning[edit]

text: Arabic Numerals (13th century)

text: The first recorded mention in Europe was in 976, and they were first widely published in 1202 by Fibonacci with his Liber Abaci.

text: University

text: The first medieval universities were founded between the 11th and 13th centuries leading to a rise in literacy and learning. By 1500, the institution had spread throughout most of Europe and played a key role in the Scientific Revolution. Today, the educational concept and institution has been globally adopted.[40]

text: Textile industry and garments[edit]

text: Functional button (13th century)

text: German buttons appeared in 13th-century Germany as an indigenous innovation.[41] They soon became widespread with the rise of snug-fitting clothing.

text: Horizontal loom (11th century)

text: Horizontal looms operated by foot-treadles were faster and more efficient.

text: Silk (6th century)

text: Manufacture of silk began in Eastern Europe in the 6th century and in Western Europe in the 11th or 12th century. Silk had been imported over the Silk Road since antiquity. The technology of "silk throwing" was mastered in Tuscany in the 13th century. The silk works used waterpower and some regard these as the first mechanized textile mills.

text: Spinning wheel (13th century)

text: Brought to Europe probably from India.

text: Miscellaneous[edit]

text: Chess (1450)

text: The earliest predecessors of the game originated in 6th-century AD India and spread via Persia and the Muslim world to Europe. Here the game evolved into its current form in the 15th century.

text: Forest glass (c. 1000)

text: This type of glass uses wood ash and sand as the main raw materials and is characterised by a variety of greenish-yellow colours.

text: Grindstones (834)

text: Grindstones are a rough stone, usually sandstone, used to sharpen iron. The first rotary grindstone (turned with a leveraged handle) occurs in the Utrecht Psalter, illustrated between 816 and 834.[42] According to Hägermann, the pen drawing is a copy of a late-antique manuscript.[43] A second crank which was mounted on the other end of the axle is depicted in the Luttrell Psalter from around 1340.[44]

text: Liquor (12th century)

text: Alcohol distillation was introduced by Pūr Sinɑʼ (Persian ابن سینا or ابو علی سینا or پور سينا Pur-e Sina; [ˈpuːr ˈsiːnɑː] "son of Sina";[full citation needed] August c. 980 – June 1037), commonly known as Ibn Sīnā, or in Arabic writing Abū ʿAlī al-Ḥusayn ibn ʿAbd Allāh ibn Al-Hasan ibn Ali ibn Sīnā. It was initially used as a medicinal elixir and was a popular remedy for the Black Death during the 14th century. Drinks such as vodka, gin and brandy come into form.

text: Magnets (12th century)

text: Magnets were first referenced in the Roman d'Enéas, composed between 1155 and 1160.

text: Mirrors (1180)

text: The first mention of a "glass" mirror is in 1180 by Alexander Neckham who said "Take away the lead which is behind the glass and there will be no image of the one looking in."

text: Illustrated surgical atlas (1345)

text: Guido da Vigevano (c. 1280 − 1349) was the first author to add illustrations to his anatomical descriptions. His Anathomia provides pictures of neuroanatomical structures and techniques such as the dissection of the head by means of trephination, and depictions of the meninges, cerebrum, and spinal cord.[45]

text: Quarantine (1377)

text: Initially a 40-day-period, the quarantine was introduced by the Republic of Ragusa as a measure of disease prevention related to the Black Death. It was later adopted by Venice from where the practice spread all around in Europe.

text: Rat traps (1170s)

text: The first mention of a rat trap is in the medieval romance Yvain, the Knight of the Lion by Chrétien de Troyes.

text: Soap (9th century)

text: Soap came into widespread European use in the 9th century in semi-liquid form, with hard soap perfected by the Arabs in the 12th century.

text: Military technologies[edit]

text: Armour[edit]

text: Quilted Armour (pre 5th - 14th Century)

text: There was a vast amount of armour technology available through the 5th to 16th centuries. Most soldiers during this time wore padded or quilted armor. This was the cheapest and most available armor for the majority of soldiers. Quilted armour was usually just a jacket made of thick linen and wool meant to pad or soften the impact of blunt weapons and light blows. Although, this technology predated the 5th century, it was still extremely prevalent because of the low cost and the weapon technology at the time made the bronze armor of the Greeks and Romans obsolete. Quilted armour was also used in conjunction with other types of armour. Usually worn over or under leather, mail, and later plate armour.[46]

text: Cuir Bouilli (5th-10th Century)

text: Hardened leather armour also called Cuir Bouilli was a step up from quilted armour. Made by boiling leather in either water, wax or oil to soften it so it can be shaped, it would then be allowed to dry and become very hard.[47] Large pieces of armour could be made such as breast plates, helmets, and leg guards, but many times smaller pieces would be sewn into the quilting of quilted armour or strips would be sewn together on the outside of a linen jacket. This was not as affordable as the quilted armour but offered much better protection against edged slashing weapons.

text: Chain Mail (11th-16th Century)

text: The most common type during the 11th through the 16th centuries was the Hauberk, also known earlier than the 11th century as the Carolingian byrnie.[48] Made of interlinked rings of metal, it sometimes consisted of a coif that covered the head and a tunic that covered the torso, arms, and legs down to the knees. Chain mail was very effective at protecting against light slashing blows but ineffective against stabbing or thrusting blows. The great advantage was that it allowed a great freedom of movement and was relatively light with significant protection over quilted or hardened leather armour. It was far more expensive than the hardened leather or quilted armour because of the massive amount of labor it required to create. This made it unattainable for most soldiers and only the more wealthy soldiers could afford it. Later, toward the end of the 13th century banded mail became popular.[49] Constructed of washer shaped rings of iron overlapped and woven together by straps of leather as opposed to the interlinked metal rings of chain mail, banded mail was much more affordable to manufacture. The washers were so tightly woven together that it was very difficult penetrate and offered greater protection from arrow and bolt attacks.[50]

text: Jazerant (11th century)

text: The Jazerant or Jazeraint was an adaptation of chain mail in which the chain mail would be sewn in between layers of linen or quilted armour.[51] Exceptional protection against light slashing weapons and slightly improved protection against small thrusting weapons, but little protection against large blunt weapons such as maces and axes. This gave birth to reinforced chain mail and became more prevalent in the 12th and 13th century. Reinforced armour was made up of chain mail with metal plates or hardened leather plates sewn in. This greatly improved protection from stabbing and thrusting blows.

text: Scale Armour (12th century)

text: A type of Lamellar armour,[52] was made up entirely of small, overlapping plates. Either sewn together, usually with leather straps, or attached to a backing such as linen, or a quilted armor. Scale armour does not require the labor to produce that chain mail does and therefore is more affordable. It also affords much better protection against thrusting blows and pointed weapons. Though, it is much heavier, more restrictive and impedes free movement.

text: Plate Armour (14th century)

text: Plate armour covered the entire body. Although parts of the body were already covered in plate armour as early as 1250, such as the Poleyns for covering the knees and Couters - plates that protected the elbows,[53] the first complete full suit without any textiles was seen around 1410-1430. [54] Components of medieval armour that made up a full suit consisted of a cuirass, a gorget, vambraces, gauntlets, cuisses, greaves, and sabatons held together by internal leather straps. Improved weaponry such as crossbows and the long bow had greatly increased range and power. This made penetration of the chain mail hauberk much easier and more common.[55] By the mid 1400's most plate was worn alone and without the need of a hauberk.[56] Advances in metal working such as the blast furnace and new techniques for carburizing made plate armour nearly impenetrable and the best armour protection available at the time. Although plate armour was fairly heavy, because each suit was custom tailored to the wearer, it was very easy to move around in. A full suit of plate armour was extremely expensive and mostly unattainable for the majority of soldiers. Only very wealthy land owners and nobility could afford it. The quality of plate armour increases as more armour makers became more proficient in metal working. A suit of plate armour became a symbol of social status and the best made were personalized with embellishments and engravings. Plate armour saw continued use in battle until the 17th century.

text: Cavalry[edit]

text: Arched saddle (11th century)

text: The arched saddle enabled mounted knights to wield lances underarm and prevent the charge from turning into an unintentional pole-vault. This innovation gave birth to true shock cavalry, enabling fighters to charge on full gallop.

text: Spurs (11th century)

text: Spurs were invented by the Normans and appeared at the same time as the cantled saddle. They enabled the horseman to control his horse with his feet, replacing the whip and leaving his arms free. Rowel spurs familiar from cowboy films were already known in the 13th century. Gilded spurs were the ultimate symbol of the knighthood - even today someone is said to "earn his spurs" by proving his or her worthiness.

text: Stirrup (6th century)

text: Stirrups were invented by steppe nomads in what is today Mongolia and northern China in the 4th century. They were introduced in Byzantium in the 6th century and in the Carolingian Empire in the 8th. They allowed a mounted knight to wield a sword and strike from a distance leading to a great advantage for mounted cavalry.

text: Gunpowder weapons[edit]

text: Cannon (1324)

text: Cannons are first recorded in Europe at the siege of Metz in 1324. In 1350 Petrarch wrote "these instruments which discharge balls of metal with most tremendous noise and flashes of fire...were a few years ago very rare and were viewed with greatest astonishment and admiration, but now they are become as common and familiar as any other kinds of arms."[1]

text: Volley gun

text: See Ribauldequin.

text: Corned gunpowder (late 14th century)

text: First practiced in Western Europe, corning the black powder allowed for more powerful and faster ignition of cannons. It also facilitated the storage and transportation of black powder. Corning constituted a crucial step in the evolution of gunpowder warfare.

text: Supergun (late 14th century)

text: Extant examples include the wrought-iron Pumhart von Steyr, Dulle Griet and Mons Meg as well as the cast-bronze Faule Mette and Faule Grete (all from the 15th century).

text: Mechanical artillery[edit]

text: Counterweight trebuchet (12th century)

text: Powered solely by the force of gravity, these catapults revolutionized medieval siege warfare and construction of fortifications by hurling huge stones unprecedented distances. Originating somewhere in the eastern Mediterranean basin, counterweight trebuchets were introduced in the Crusader states by the 1120s, Byzantium by the 1130s and in the Latin West by the second half of the century.[57]

text: Missile weapons[edit]

text: Longbow with massed, disciplined archery (13th century)

text: Having a high rate of fire and penetration power, the longbow contributed to the eventual demise of the medieval knight class[dubious – discuss]. Used particularly by the English to great effect against the French cavalry during the Hundred Years' War (1337–1453).

text: Steel crossbow (late 14th century)

text: European innovation. Came with several different cocking aids to enhance draw power, making the weapons also the first hand-held mechanical crossbows.

text: Miscellaneous[edit]

text: Combined arms tactics (14th century)

text: The battle of Halidon Hill 1333 was the first battle where intentional and disciplined combined arms infantry tactics were employed.[dubious – discuss] The English men-at-arms dismounted aside the archers, combining thus the staying power of super-heavy infantry and striking power of their two-handed weapons with the missiles and mobility of the archers using longbows and shortbows . Combining dismounted knights and men-at-arms with archers was the archetypal Western Medieval battle tactics until the battle of Flodden 1513 and final emergence of firearms.

text: Gallery[edit]

text:
Longbowmen (c. 1493)

Cranked rack-and-pinion device for cocking a crossbow (c. 1493)

Organ gun in the Bellifortis (c. 1405)