document_title: Lightning

question_text: where can lightning take place that is where can it begin and end

question_tokens: where can lightning take place that is where can it begin and end

text: Lightning

text: Lightning electrification[edit]

text: The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 Celsius, see figure to the right. At that place, the combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air.[1]

text: The differences in the movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. See figure to the left. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward the lower part of the storm.[1]

text: The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged.[1]

text: The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures.[1]

text: General considerations[edit]

text: On Earth, the lightning frequency is approximately 40–50 times a second or nearly 1.4 billion flashes per year[2] and the average duration is 0.2 seconds made up from a number of much shorter flashes (strokes) of around 30 microseconds.[3]

text: Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude, prevailing wind currents, relative humidity, proximity to warm and cold bodies of water, etc. To a certain degree, the ratio between IC (in-cloud or intracloud), CC (cloud-to-cloud) and CG (cloud-to-ground) lightning may also vary by season in middle latitudes. Because human beings are terrestrial and most of their possessions are on the Earth where lightning can damage or destroy them, CG lightning is the most studied and best understood of the three types, even though IC and CC are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation.

text: A typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within the cloud to the ground's surface. The actual discharge is the final stage of a very complex process.[4] At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute.[5] Lightning primarily occurs when warm air is mixed with colder air masses,[6] resulting in atmospheric disturbances necessary for polarizing the atmosphere.[citation needed] However, it can also occur during dust storms, forest fires, tornadoes, volcanic eruptions, and even in the cold of winter, where the lightning is known as thundersnow.[7][8] Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center.[9][10][11]

text: The science of lightning is called fulminology, and the fear of lightning is called astraphobia.

text: Frequency[edit]

text: Lightning is not distributed evenly around the planet, as shown in the map.

text: About 70% of lightning occurs over land in the tropics[12] where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses, as well as differences in moisture concentrations, and it generally happens at the boundaries between them. The flow of warm ocean currents past drier land masses, such as the Gulf Stream, partially explains the elevated frequency of lightning in the Southeast United States. Because the influence of small or absent land masses in the vast stretches of the world's oceans limits the differences between these variants in the atmosphere, lightning is notably less frequent there than over larger landforms. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least amount of lightning.

text: In general, cloud-to-ground (CG) lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel) develops a negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge.

text: Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and the ground, the proportion of CG strikes (versus cloud-to-cloud (CC) or in-cloud (IC) discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG.[13][14]

text: Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.6–1.25 miles) above the ground and tops up to 15 km (9.3 mi) in height.

text: Lightning hotspots: The place on Earth where lightning occurs most often is near the small village of Kifuka in the mountains of the eastern Democratic Republic of the Congo,[15] where the elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per 1 square kilometer (0.39 sq mi) per year.[16] Lake Maracaibo in Venezuela averages 297 days per year with lightning activity.[17] Other lightning hotspots include Catatumbo in Venezuela, Singapore,[18] and Lightning Alley in Central Florida.[19][20]

text: Necessary conditions[edit]

text: In order for an electrostatic discharge to occur, two preconditions are necessary: firstly, a sufficiently high electric potential between two regions of space must exist, and secondly, a high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges.

text: It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however the exact processes by which this occurs are not fully understood.[21]

text: The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. This is overcome by "lightning", a complex process referred to as the lightning "flash".

text: Electrical field generation[edit]

text: As a thundercloud moves over the surface of the Earth, an equal electric charge, but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as a bell curve.

text: The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field.

text: Flashes and strikes[edit]

text: The best studied and understood form of lightning is cloud to ground (CG). Although more common, intracloud (IC) and cloud to cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside the clouds. Also, given the very low probability lightning will strike the same point repeatedly and consistently, scientific inquiry is difficult at best even in the areas of high CG frequency. As such, knowing flash propagation is similar amongst all forms of lightning, the best means to describe the process is through an examination of the most studied form, cloud to ground.

text: Lightning leaders[edit]

text: In a process not well understood, a bidirectional channel of ionized air, called a "leader", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with a charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern.[22] In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of the leaders can be readily observed in slow-motion videos of lightning flashes.

text: It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash, a bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground.

text: The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in a number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it get closer to the Earth's surface.

text: About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length.[23] The establishment of the ionic channel takes a comparatively long amount of time (hundreds of milliseconds) in comparison to the resulting discharge, which occurs within a few microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes, is dwarfed by subsequent currents during the actual discharge.

text: Initiation of the lightning leaders is not well understood. The electric field strength within the thundercloud is not typically large enough to initiate this process by itself.[24] Many hypotheses have been proposed. One theory postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown. As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another theory invokes locally enhanced electric fields being formed near elongated water droplets or ice crystals.[25] Percolation theory, especially for the case of biased percolation,[26] [clarification needed] describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes.

text: Upward streamers[edit]

text: When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field. The electric field is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer, can develop from these points. This was first theorized by Heinz Kasemir.[27][28]

text: As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge exceed a threshold and form upward streamers.

text: Attachment[edit]

text: Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are.

text: Discharge[edit]

text: Return stroke[edit]

text: Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at a fraction of the speed of light. This is the 'return stroke' and it is the most luminous and noticeable part of the lightning discharge.

text: A large electric current flows along the plasma channel from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of the ground. Called step potentials, they are responsible for more injuries and deaths than the strike itself.[citation needed] Electricity takes every path available to it.[29] A portion of the return stroke current will often preferentially flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes.

text: The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground to cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 1×108 m/s.[30]

text: The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 50,000 K, causing it to brilliantly radiate with a blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder.

text: Re-strike[edit]

text: High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30.[31]

text: Each re-strike is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable "strobe light" effect.[32]

text: To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following the negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders, usually decay shortly after their formation. When they do manage to make contact with a conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all, or a portion of the length of the original leader. The dart leaders making connections with the ground is what causes a majority of subsequent return strokes.[33]

text: Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than the initial return stroke. Each subsequent stroke usually re-uses the discharge channel taken by the previous one, but the channel may be offset from its previous position as wind displaces the hot channel.[34]

text: Since recoil and dart leader processes do not occur on negative leaders, subsequent return strokes very seldom utilize the same channel on positive ground flashes which are explained later in the article.[33]

text: Transient currents during flash[edit]

text: The electric current within a typical negative CG lightning discharge rises very quickly to its peak value in 1–10 microseconds, then decays more slowly over 50–200 microseconds. The transient nature of the current within a lightning flash results in several phenomena that need to be addressed in the effective protection of ground-based structures. Rapidly changing currents tend to travel on the surface of a conductor, in what is called the skin effect, unlike direct currents, which "flow through" the entire conductor like water through a hose. Hence, conductors used in the protection of facilities tend to be multi-stranded, with small wires woven together. This increases the total bundle surface area in inverse proportion to the individual strand radius, for a fixed total cross-sectional area.

text: The rapidly changing currents also create electromagnetic pulses (EMPs) that radiate outward from the ionic channel. This is a characteristic of all electrical discharges. The radiated pulses rapidly weaken as their distance from the origin increases. However, if they pass over conductive elements such as power lines, communication lines, or metallic pipes, they may induce a current which travels outward to its termination. This is the "surge" that, more often than not, results in the destruction of delicate electronics, electrical appliances, or electric motors. Devices known as surge protectors (SPD) or transient voltage surge suppressors (TVSS) attached in parallel with these lines can detect the lightning flash's transient irregular current, and, through an alteration of its physical properties, route the spike to an attached earthing ground, thereby protecting the equipment from damage.

text: Types[edit]

text: There are three primary types of lightning, defined by what is at the "ends" of a flash channel.

text:
Intracloud (IC), which occurs within a single thundercloud unit
Cloud to cloud (CC) or intercloud, which starts and ends between two different "functional" thundercloud units
Cloud to ground (CG), that primarily originates in the thundercloud and terminates on an Earth surface, but may also occur in the reverse direction, that is ground to cloud

text: There are variations of each type, such as "positive" versus "negative" CG flashes, that have different physical characteristics common to each which can be measured. Different common names used to describe a particular lightning event may be attributed to the same or different events.

text: Cloud to ground (CG)[edit]

text: Cloud-to-ground (CG) lightning is a lightning discharge between a thundercloud and the ground. It is initiated by a stepped leader moving down from the cloud, which is met by a streamer moving up from the ground.

text: CG is the least common, but best understood of all types of lightning. It is easier to study scientifically, because it terminates on a physical object, namely the Earth, and lends itself to being measured by instruments on the ground. Of the three primary types of lightning, it poses the greatest threat to life and property since it terminates or "strikes" the Earth. The overall discharge, termed a flash, is composed of a number of processes such as preliminary breakdown, stepped leaders, connecting leaders, return strokes, dart leaders and subsequent return strokes.[35]

text: Positive and negative lightning[edit]

text: Cloud-to-ground (CG) lightning is either positive or negative, as defined by the direction of the conventional electric current from cloud to ground. Most CG lightning is negative, meaning that a negative charge is transferred to ground and electrons travel downward along the lightning channel. The reverse happens in a positive CG flash, where electrons travel upward along the lightning channel and a positive charge is transferred to the ground. Positive lightning is less common than negative lightning, and on average makes up less than 5% of all lightning strikes.[36]

text: There are six different mechanisms theorized to result in the formation of downward positive lightning.[37]

text:
Vertical wind shear displacing the upper positive charge region of a thundercloud, exposing it to the ground below.
The loss of lower charge regions in the dissipating stage of a thunderstorm, leaving the primary positive charge region.
A complex arrangement of charge regions in a thundercloud, effectively resulting in an inverted dipole or inverted tripole in which the main negative charge region is above the main positive charge region instead of beneath it.
An unusually large lower positive charge region in the thundercloud.
Cutoff of an extended negative leader from its origin which creates a new bidirectional leader in which the positive end strikes the ground, commonly seen in anvil-crawler spider flashes.
The initiation of a downward positive branch from an intracloud lightning flash.

text: Contrary to popular belief, positive lightning flashes do not necessarily originate from the anvil or the upper positive charge region and strike a rain-free area outside of the thunderstorm. This belief is based on the outdated idea that lightning leaders are unipolar in nature and originating from their respective charge region.

text: Positive lightning strikes tend to be much more intense than their negative counterparts. An average bolt of negative lightning carries an electric current of 30,000 amperes (30 kA), and transfers 15 coulombs of electric charge and 500 megajoules of energy. Large bolts of negative lightning can carry up to 120 kA and 350 coulombs.[38] The average positive ground flash has roughly double the peak current of a typical negative flash, and can produce peak currents up to 400,000 amperes (400 kA) and charges of several hundreds coulombs.[39][40] Furthermore, positive ground flashes with high peak currents are commonly followed by long continuing currents, a correlation not seen in negative ground flashes.[41]

text: As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. Due to the aforementioned tendency for positive ground flashes to produce both high peak currents and long continuing current, they are capable of heating surfaces to much higher levels which increases the likelihood of a fire being ignited.

text: Positive lightning has also been shown to trigger the occurrence of upward lightning flashes from the tops of tall structures and is largely responsible for the initiation of sprites several tens of kilometers above ground level. Positive lightning tends to occur more frequently in winter storms, as with thundersnow, during intense tornadoes[42] and in the dissipation stage of a thunderstorm.[43] Huge quantities of extremely low frequency (ELF) and very low frequency (VLF) radio waves are also generated.[44]

text: A unique form of cloud-to-ground lightning exists where lightning appears to exit from the cumulonimbus cloud and propagate a considerable distance through clear air before veering towards, and striking, the ground. For this reason, they are known as "bolts from the blue". Despite the popular misconception that these are positive lightning strikes due to them seemingly originating from the positive charge region, observations have shown that these are in fact negative flashes. They begin as intracloud flashes within the cloud, the negative leader then exits the cloud from the positive charge region before propagating through clear air and striking the ground some distance away.[45][46]

text: Cloud to cloud (CC) and intra-cloud (IC)[edit]

text: Lightning discharges may occur between areas of cloud without contacting the ground. When it occurs between two separate clouds it is known as inter-cloud lightning, and when it occurs between areas of differing electric potential within a single cloud it is known as intra-cloud lightning. Intra-cloud lightning is the most frequently occurring type.[43]

text: Intra-cloud lightning most commonly occurs between the upper anvil portion and lower reaches of a given thunderstorm. This lightning can sometimes be observed at great distances at night as so-called "sheet lightning". In such instances, the observer may see only a flash of light without hearing any thunder.

text: Another term used for cloud–cloud or cloud–cloud–ground lightning is "Anvil Crawler", due to the habit of charge, typically originating beneath or within the anvil and scrambling through the upper cloud layers of a thunderstorm, often generating dramatic multiple branch strokes. These are usually seen as a thunderstorm passes over the observer or begins to decay. The most vivid crawler behavior occurs in well developed thunderstorms that feature extensive rear anvil shearing.

text: Observational variations[edit]

text:
Anvil crawler lightning, sometimes called Spider lightning is created when leaders propagate through horizontally-extensive charge regions in mature thunderstorms, usually the stratiform regions of mesoscale convective systems. These discharges usually begin as intracloud discharges originating within the convective region; the negative leader end then propagates well into the aforementioned charge regions in the stratiform area. If the leader becomes too long, it may separate into multiple bidirectional leaders. When this happens, the positive end of the separated leader may strike the ground as a positive CG flash or crawl on the underside of the cloud, creating a spectacular display of lightning crawling across the sky. Ground flashes produced in this manner tend to transfer high amounts of charge, and this can trigger upward lightning flashes and upper-atmospheric lightning.[33]
Ball lightning may be an atmospheric electrical phenomenon, the physical nature of which is still controversial. The term refers to reports of luminous, usually spherical objects which vary from pea-sized to several meters in diameter.[47] It is sometimes associated with thunderstorms, but unlike lightning flashes, which last only a fraction of a second, ball lightning reportedly lasts many seconds. Ball lightning has been described by eyewitnesses but rarely recorded by meteorologists.[48][49] Scientific data on natural ball lightning is scarce owing to its infrequency and unpredictability. The presumption of its existence is based on reported public sightings, and has therefore produced somewhat inconsistent findings. Brett Porter,[50] wildlife ranger, reported having taken a photo at Queensland of Australia in 1987.

text:
Bead lightning is the decaying stage of a lightning channel in which the luminosity of the channel breaks up into segments. Nearly every lightning discharge will exhibit beading as the channel cools immediately after a return stroke, sometimes referred to as the lightning's 'bead-out' stage. 'Bead lightning' is more properly a stage of a normal lightning discharge rather than a type of lightning in itself. Beading of a lightning channel is usually a small-scale feature, and therefore is often only apparent when the observer/camera is close to the lightning.[51]
Cloud-to-air lightning is a lightning flash in which one end of a bidirectional leader exits the cloud, but does not result in a ground flash. Such flashes can sometimes be thought of as failed ground flashes. Blue jets and gigantic jets are a form of cloud-to-air or cloud-to-ionosphere lightning where a leader is launched from the top of a thunderstorm.
Dry lightning is used in Australia, Canada and the United States for lightning that occurs with no precipitation at the surface. This type of lightning is the most common natural cause of wildfires.[52] Pyrocumulus clouds produce lightning for the same reason that it is produced by cumulonimbus clouds[citation needed].

text:
Forked lightning is cloud-to-ground lightning that exhibits branching of its path.
Heat lightning is a lightning flash that appears to produce no discernible thunder because it occurs too far away for the thunder to be heard. The sound waves dissipate before they reach the observer.[53]

text:
Ribbon lightning occurs in thunderstorms with high cross winds and multiple return strokes. The wind will blow each successive return stroke slightly to one side of the previous return stroke, causing a ribbon effect.[54]
Rocket lightning is a form of cloud discharge, generally horizontal and at cloud base, with a luminous channel appearing to advance through the air with visually resolvable speed, often intermittently.[55]

text: Sheet lightning is cloud-to-cloud lightning that exhibits a diffuse brightening of the surface of a cloud, caused by the actual discharge path being hidden or too far away. The lightning itself cannot be seen by the spectator, so it appears as only a flash, or a sheet of light. The lightning may be too far away to discern individual flashes.

text:
Smooth channel lightning is an informal term referring to a type of cloud-to-ground lightning strike that has no visible branching and appears like a line with smooth curves as opposed to the jagged appearance of most lightning channels. They are a form of positive lightning generally observed in or near the convective regions of severe thunderstorms in the north central United States. It is theorized that severe thunderstorms in this region obtain an "inverted tripole" charge structure in which the main positive charge region is located below the main negative charge region instead of above it, and as a result these thunderstorms generate predominantly positive cloud-to-ground lightning. The term "smooth channel lightning" is also sometimes attributed to upward ground-to-cloud lightning flashes, which are generally negative flashes initiated by upward positive leaders from tall structures.
Staccato lightning is a cloud-to-ground lightning (CG) strike which is a short-duration stroke that (often but not always) appears as a single very bright flash and often has considerable branching.[56] These are often found in the visual vault area near the mesocyclone of rotating thunderstorms and coincides with intensification of thunderstorm updrafts. A similar cloud-to-cloud strike consisting of a brief flash over a small area, appearing like a blip, also occurs in a similar area of rotating updrafts.[57]

text: Superbolts are bolts of lightning around a hundred times brighter than normal. On Earth, one in a million lightning strikes is a superbolt.[58][59]

text: Sympathetic lightning is the tendency of lightning to be loosely coordinated across long distances. Discharges can appear in clusters when viewed from space.

text:
Upward lightning or ground-to-cloud lightning is a lightning flash which originates from the top of a grounded object and propagates upward from this point. This type of lightning can be triggered by a preceding lightning flash, or it may initiate entirely on its own. The former is generally found in regions where spider lightning occurs, and may involve multiple grounded objects simultaneously. The latter usually occurs during the cold season and may be the dominant lightning type in thundersnow events.[60]
Clear-air lightning describes lightning that occurs with no apparent cloud close enough to have produced it. In the U.S. and Canadian Rockies, a thunderstorm can be in an adjacent valley and not observable from the valley where the lightning bolt strikes, either visually or audibly. European and Asian mountainous areas experience similar events. Also in areas such as sounds, large lakes or open plains, when the storm cell is on the near horizon (within 26 km (16 mi)) there may be some distant activity, a strike can occur and as the storm is so far away, the strike is referred to as a bolt from the blue.[61] These flashes usually begin as normal intracloud lightning flashes before the negative leader exits the cloud and strikes the ground a considerable distance away.[45][46] Positive clear-air strikes can occur in highly sheared environments where the upper positive charge region becomes horizontally displaced from the precipitation area.[62]

text: Effects[edit]

text: Lightning strike[edit]

text: Objects struck by lightning experience heat and magnetic forces of great magnitude. The heat created by lightning currents traveling through a tree may vaporize its sap, causing a steam explosion that bursts the trunk. As lightning travels through sandy soil, the soil surrounding the plasma channel may melt, forming tubular structures called fulgurites. Even though roughly 90 percent of people struck by lightning survive,[63] humans or animals struck by lightning may suffer severe injury due to internal organ and nervous system damage. Buildings or tall structures hit by lightning may be damaged as the lightning seeks unintended paths to ground. By safely conducting a lightning strike to ground, a lightning protection system can greatly reduce the probability of severe property damage. Lightning also serves an important role in the nitrogen cycle by oxidizing diatomic nitrogen in the air into nitrates which are deposited by rain and can fertilize the growth of plants and other organisms.[64][65]

text: Thunder[edit]

text: Because the electrostatic discharge of terrestrial lightning superheats the air to plasma temperatures along the length of the discharge channel in a short duration, kinetic theory dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a shock wave audible as thunder. Since the sound waves propagate not from a single point source but along the length of the lightning's path, the sound origin's varying distances from the observer can generate a rolling or rumbling effect. Perception of the sonic characteristics is further complicated by factors such as the irregular and possibly branching geometry of the lightning channel, by acoustic echoing from terrain, and by the typically multiple-stroke characteristic of the lightning strike.

text: Light travels at about 300,000,000 m/s, and sound travels through air at about 340 m/s. An observer can approximate the distance to the strike by timing the interval between the visible lightning and the audible thunder it generates. A lightning flash preceding its thunder by one second would be approximately 340 m (0.21 mi) in distance; a delay of three seconds would indicate a distance of about one kilometer (0.62 mi) (3×340 m). A flash preceding thunder by five seconds would indicate a distance of approximately one mile (1.6 km) (5×340 m). Consequently, a lightning strike observed at a very close distance will be accompanied by a sudden clap of thunder, with almost no perceptible time lapse, possibly accompanied by the smell of ozone (O3).

text: High-energy radiation[edit]

text: The production of X-rays by a bolt of lightning was theoretically predicted as early as 1925[66] but no evidence was found until 2001/2002,[67][68][69] when researchers at the New Mexico Institute of Mining and Technology detected X-ray emissions from an induced lightning strike along a grounded wire trailed behind a rocket shot into a storm cloud. In the same year University of Florida and Florida Tech researchers used an array of electric field and X-ray detectors at a lightning research facility in North Florida to confirm that natural lightning makes X-rays in large quantities during the propagation of stepped leaders. The cause of the X-ray emissions is still a matter for research, as the temperature of lightning is too low to account for the X-rays observed.[70][71]

text: A number of observations by space-based telescopes have revealed even higher energy gamma ray emissions, the so-called terrestrial gamma-ray flashes (TGFs). These observations pose a challenge to current theories of lightning, especially with the recent discovery of the clear signatures of antimatter produced in lightning.[72] Recent research has shown that secondary species, produced by these TGFs, such as electrons, positrons, neutrons or protons, can gain energies of up to several tens of MeV.[73][74]

text: Volcanic[edit]

text: Volcanic activity produces lightning-friendly conditions in multiple ways. The enormous quantity of pulverized material and gases explosively ejected into the atmosphere creates a dense plume of particles. The ash density and constant motion within the volcanic plume produces charge by frictional interactions (triboelectrification), resulting in very powerful and very frequent flashes as the cloud attempts to neutralize itself. Due to the extensive solid material (ash) content, unlike the water rich charge generating zones of a normal thundercloud, it is often called a dirty thunderstorm.

text:
Powerful and frequent flashes have been witnessed in the volcanic plume as far back as the 79 AD eruption of Vesuvius by Pliny The Younger.[75]
Likewise, vapors and ash originating from vents on the volcano's flanks may produce more localized and smaller flashes upwards of 2.9 km long.
Small, short duration sparks, recently documented near newly extruded magma, attest to the material being highly charged prior to even entering the atmosphere.[76]

text: Extraterrestrial[edit]

text: Lightning has been observed within the atmospheres of other planets, such as Jupiter and Saturn. Although in the minority on Earth, superbolts appear to be common on Jupiter.

text: Lightning on Venus has been a controversial subject after decades of study. During the Soviet Venera and U.S. Pioneer missions of the 1970s and 1980s, signals suggesting lightning may be present in the upper atmosphere were detected.[77] Although the Cassini–Huygens mission fly-by of Venus in 1999 detected no signs of lightning, the observation window lasted mere hours. Radio pulses recorded by the spacecraft Venus Express (which began orbiting Venus in April 2006) may originate from lightning on Venus.

text: Human-related phenomena[edit]

text:
Airplane contrails have also been observed to influence lightning to a small degree. The water vapor-dense contrails of airplanes may provide a lower resistance pathway through the atmosphere having some influence upon the establishment of an ionic pathway for a lightning flash to follow.[78]
Rocket exhaust plumes provided a pathway for lightning when it was witnessed striking the Apollo 12 rocket shortly after takeoff.
Thermonuclear explosions by providing extra material for electrical conduction and a very turbulent localized atmosphere, have been seen triggering lightning flashes within the mushroom cloud. In addition, intense gamma radiation from large nuclear explosions may develop intensely charged regions in the surrounding air through Compton scattering. The intensely charged space charge regions create multiple clear-air lightning discharges shortly after the device detonates.[79]

text: Scientific study[edit]

text: Properties[edit]

text: Thunder is heard as a rolling, gradually dissipating rumble because the sound from different portions of a long stroke arrives at slightly different times.[80]

text: When the local electric field exceeds the dielectric strength of damp air (about 3 million volts per meter), electrical discharge results in a strike, often followed by commensurate discharges branching from the same path. (See image, right.) Mechanisms that cause the charges to build up to lightning are still a matter of scientific investigation.[81][82] New study confirming dielectric breakdown is involved. Rison 2016. Lightning may be caused by the circulation of warm moisture-filled air through electric fields.[83] Ice or water particles then accumulate charge as in a Van de Graaff generator.[84]

text: Researchers at the University of Florida found that the final one-dimensional speeds of 10 flashes observed were between 1.0×105 and 1.4×106 m/s, with an average of 4.4×105 m/s.[85]

text: Detection and monitoring[edit]

text: The earliest detector invented to warn of the approach of a thunder storm was the lightning bell. Benjamin Franklin installed one such device in his house.[86] [87] The detector was based on an electrostatic device called the 'electric chimes' invented by Andrew Gordon in 1742.

text: Lightning discharges generate a wide range of electromagnetic radiations, including radio-frequency pulses. The times at which a pulse from a given lightning discharge arrives at several receivers can be used to locate the source of the discharge. The United States federal government has constructed a nationwide grid of such lightning detectors, allowing lightning discharges to be tracked in real time throughout the continental U.S.[88][89]

text: The Earth-ionosphere waveguide traps electromagnetic VLF- and ELF waves. Electromagnetic pulses transmitted by lightning strikes propagate within that waveguide. The waveguide is dispersive, which means that their group velocity depends on frequency. The difference of the group time delay of a lightning pulse at adjacent frequencies is proportional to the distance between transmitter and receiver. Together with direction finding methods, this allows to locate lightning strikes up to distances of 10,000 km from their origin. Moreover, the eigenfrequencies of the Earth-ionospheric waveguide, the Schumann resonances at about 7.5 Hz, are used to determine the global thunderstorm activity.[90]

text: In addition to ground-based lightning detection, several instruments aboard satellites have been constructed to observe lightning distribution. These include the Optical Transient Detector (OTD), aboard the OrbView-1 satellite launched on April 3, 1995, and the subsequent Lightning Imaging Sensor (LIS) aboard TRMM launched on November 28, 1997.[91][92][93]

text: Artificially triggered[edit]

text:
Rocket-triggered lightning can be "triggered" by launching specially designed rockets trailing spools of wire into thunderstorms. The wire unwinds as the rocket ascends, creating an elevated ground that can attract descending leaders. If a leader attaches, the wire provides a low-resistance pathway for a lightning flash to occur. The wire is vaporized by the return current flow, creating a straight lightning plasma channel in its place. This method allows for scientific research of lightning to occur under a more controlled and predictable manner.[94]

The International Center for Lightning Research and Testing (ICLRT) at Camp Blanding, Florida typically uses rocket triggered lightning in their research studies.

Laser-triggered

Since the 1970s,[95][96][97][98][99][100] researchers have attempted to trigger lightning strikes by means of infrared or ultraviolet lasers, which create a channel of ionized gas through which the lightning would be conducted to ground. Such triggering of lightning is intended to protect rocket launching pads, electric power facilities, and other sensitive targets.[101][102][103][104][105]
In New Mexico, U.S., scientists tested a new terawatt laser which provoked lightning. Scientists fired ultra-fast pulses from an extremely powerful laser thus sending several terawatts into the clouds to call down electrical discharges in storm clouds over the region. The laser beams sent from the laser make channels of ionized molecules known as "filaments". Before the lightning strikes earth, the filaments lead electricity through the clouds, playing the role of lightning rods. Researchers generated filaments that lived a period too short to trigger a real lightning strike. Nevertheless, a boost in electrical activity within the clouds was registered. According to the French and German scientists who ran the experiment, the fast pulses sent from the laser will be able to provoke lightning strikes on demand.[106] Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed—in effect they generated small local discharges located at the position of the plasma channels.[107]

text: Physical manifestations[edit]

text: Magnetism[edit]

text: The movement of electrical charges produces a magnetic field (see electromagnetism). The intense currents of a lightning discharge create a fleeting but very strong magnetic field. Where the lightning current path passes through rock, soil, or metal these materials can become permanently magnetized. This effect is known as lightning-induced remanent magnetism, or LIRM. These currents follow the least resistive path, often horizontally near the surface[108][109] but sometimes vertically, where faults, ore bodies, or ground water offers a less resistive path.[110] One theory suggests that lodestones, natural magnets encountered in ancient times, were created in this manner.[111]

text: Lightning-induced magnetic anomalies can be mapped in the ground,[112][113] and analysis of magnetized materials can confirm lightning was the source of the magnetization[114] and provide an estimate of the peak current of the lightning discharge.[115]

text: Solar wind and cosmic rays[edit]

text: Some high energy cosmic rays produced by supernovas as well as solar particles from the solar wind, enter the atmosphere and electrify the air, which may create pathways for lightning bolts.[116]

text: In culture and religion[edit]

text: In many cultures, lightning has been viewed as part of a deity or a deity in and of itself. These include the Greek god Zeus, the Aztec god Tlaloc, the Mayan God K, Slavic mythology's Perun, the Baltic Pērkons/Perkūnas, Thor in Norse mythology, Ukko in Finnish mythology, the Hindu god Indra, and the Shinto god Raijin.[117] In the traditional religion of the African Bantu tribes, lightning is a sign of the ire of the gods. Verses in the Jewish religion and in Islam also ascribe supernatural importance to lightning. In Christianity, the Second Coming of Jesus is compared to lightning.[Matthew 24:27][Luke 17:24]

text: The expression "Lightning never strikes twice (in the same place)" is similar to "Opportunity never knocks twice" in the vein of a "once in a lifetime" opportunity, i.e., something that is generally considered improbable. Lightning occurs frequently and more so in specific areas. Since various factors alter the probability of strikes at any given location, repeat lightning strikes have a very low probability (but are not impossible).[118][119] Similarly, "A bolt from the blue" refers to something totally unexpected.

text: Some political parties use lightning flashes as a symbol of power, such as the People's Action Party in Singapore, the British Union of Fascists during the 1930s, and the National States' Rights Party in the United States during the 1950s.[120] The Schutzstaffel, the paramilitary wing of the Nazi Party, used the Sig rune in their logo which symbolizes lightning. The German word Blitzkrieg, which means "lightning war", was a major offensive strategy of the German army during World War II.

text: In French and Italian, the expression for "Love at first sight" is coup de foudre and colpo di fulmine, respectively, which literally translated means "lightning strike". Some European languages have a separate word for lightning which strikes the ground (as opposed to lightning in general); often it is a cognate of the English word "rays". The name of New Zealand's most celebrated thoroughbred horse, Phar Lap, derives from the shared Zhuang and Thai word for lightning.[121]

text: The bolt of lightning in heraldry is called a thunderbolt and is shown as a zigzag with non-pointed ends. This symbol usually represents power and speed.

text: The lightning bolt is used to represent the instantaneous communication capabilities of electrically powered telegraphs and radios. It was a commonly used motif in Art Deco design, especially the zig-zag Art Deco design of the late 1920s.[122] The lightning bolt is a common insignia for military communications units throughout the world. A lightning bolt is also the NATO symbol for a signal asset.

text: The Unicode symbol for lightning is ☇ U+2607


document_title: Dairy cattle

question_text: how long does a cow give milk after calving

root

text: Dairy cattle

text: Management[edit]

text: Dairy cows may be found either in herds or dairy farms where dairy farmers own, manage, care for, and collect milk from them, or on commercial farms.  Herd sizes vary around the world depending on landholding culture and social structure. The United States has 9 million cows in 75,000 dairy herds, with  an average herd size of 120 cows. The number of small herds is falling rapidly with the 3,100 herds with over 500 cows producing 51% of U.S. milk in 2007.[5] The United Kingdom dairy herd overall has nearly 1.5 million cows, with about 100 head reported on an average farm.[6] In New Zealand, the average herd has more than 375 cows, while in Australia, there are approximately 220 cows in the average herd.[7][8]

tag: p

text: Dairy farming, like many other livestock raring, can be split into intensive and extensive management systems. [9]

text: Intensive systems focus towards maximum production per cow in the herd. This involve formulating their diet to provide ideal nutrition and housing the cows in a confinement system such as free stall or tie stall. These cows are housed indoors throughout their lactation and may be put to pasture during their 60-day dry period before ideally calving again. Free stall style barns involve cattle loosely housed where they can have free access to feed, water, and stalls but are moved to another part of the barn to be milked multiple times a day. In a tie stall system, the milking units are brought to the cows during each milking. These cattle are tethered within their stalls with free access to water and feed are provided. In extensive systems, cattle are mainly outside on pasture for most of their lives. These cattle are generally lower in milk production and are herded multiple times daily to be milked. The systems used greatly depends on the climate and available land of the region of which the farm is situated. [9]

text: To maintain lactation, a dairy cow must be bred and produce calves.  Depending on market conditions, the cow may be bred with a "dairy bull" or a "beef bull."  Female calves (heifers) with dairy breeding may be kept as replacement cows for the dairy herd.  If a replacement cow turns out to be a substandard producer of milk, she then goes to market and can be slaughtered for beef.  Male calves can either be used later as a breeding bull or sold and used for veal or beef.  Dairy farmers usually begin breeding or artificially inseminating heifers around 13 months of age.[10] A cow's gestation period is approximately nine months.[11] Newborn calves are removed from their mothers quickly, usually within three days, as the mother/calf bond intensifies over time and delayed separation can cause extreme stress on both cow and calf.[12]

text: Domestic cows can live to 20 years; however, those raised for dairy rarely live that long, as the average cow is removed from the dairy herd around age four and marketed for beef.[11][13] In 2014, approximately 9.5% of the cattle slaughtered in the U.S. were culled dairy cows:  cows that can no longer be seen as an economic asset to the dairy farm.[14] These animals may be sold due to reproductive problems or common diseases of milk cows such as mastitis and lameness.[13]

text: Calf[edit]

text: Most heifers (female calves) are kept on farm to be raised as a replacement heifer, a female that will be bred and enter the production cycle. Market calves are generally sold at two weeks of age and bull calves may fetch a premium over heifers due to their size, either current or potential.  Calves may be sold for veal, or for one of several types of beef production, depending on available local crops and markets. Such bull calves may be castrated if turnout onto pastures is envisaged, in order to render the animals less aggressive. Purebred bulls from elite cows may be put into progeny testing schemes to find out whether they might become superior sires for breeding. Such animals may become extremely valuable.

text: Most dairy farms separate calves from their mothers within a day of birth to reduce transmission of disease and simplify management of milking cows. Studies have been done allowing calves to remain with their mothers for 1, 4, 7 or 14 days after birth. Cows whose calves were removed longer than one day after birth showed increased searching, sniffing and vocalizations. However, calves allowed to remain with their mothers for longer periods showed weight gains at three times the rate of early removals as well as more searching behavior and better social relationships with other calves.[15][16]

text: After separation, some young dairy calves subsist on commercial milk replacer, a feed based on dried milk powder. Milk replacer is an economical alternative to feeding whole milk because it is cheaper, can be bought at varying fat and protein percentages, and is typically less contaminated than whole milk when handled properly. Some farms pasteurize and feed calves milk from the cows in the herd instead of using replacer. A day-old calf consumes around 5 liters of milk per day.

text: Cattle are social animals; their ancestors tended to live in matriarchal groups of mothers and offspring. The formation of “friendships” between two cows is common and long lasting. Traditionally individual housing systems were used in calf rearing, to reduce the risk of disease spread and provide specific care. However, due to their social behaviour the grouping of offspring may be better for the calves' overall welfare. Social interaction between the calves can have a positive effect on their growth. It has been seen that calves housed in grouped penning were found to eat more feed than those in single pens,[17] suggesting social facilitation of feeding behaviour in the calves. Play behaviour in pre-weaned dairy calves has also been suggested to help build social skills for later in life. It has been seen that those reared in grouped housing are more likely to become the dominant cattle in a new combination of animals.[18] These dominant animals have a priority choice of feed or lying areas and are generally stronger animals. Due to these reasons, it has become common practice to group or pair calves in their housing. It has become common within Canada to see paired or grouped housing in outdoor hutches or within an indoor pack penning.[citation needed]

text: Bull[edit]

text: A bull calf with high genetic potential may be reared for breeding purposes.  It may be kept by a dairy farm as a herd bull, to provide natural breeding for the herd of cows.  A bull may service up to 50 or 60 cows during a breeding season.  Any more and the sperm count will decline, leading to cows "returning to service" (to be bred again).  A herd bull may only stay for one season, as when most bulls reach over two years old their temperament becomes too unpredictable.

text: Bull calves intended for breeding commonly are bred on specialized dairy breeding farms, not production farms.  These farms are the major source of stocks for artificial insemination.

text: Milk production levels[edit]

text: The dairy cow will produce large amounts of milk in its lifetime. Production levels peak at around 40 to 60 days after calving. Production declines steadily afterwards until milking is stopped at about 10 months. The cow is "dried off" for about sixty days before calving again. Within a 12 to 14-month inter-calving cycle, the milking period is about 305 days or 10 months long.[19][20][21] Among many variables, certain breeds produce more milk than others within a range of around 6,800 to 17,000 kg (15,000 to 37,500 lbs) of milk per year.[citation needed]

text: The Holstein Friesian is the main breed of dairy cattle in Australia, and said to have the "world's highest" productivity, at 10000L of milk per year.[22] The average for a single dairy cow in the US in 2007 was 9164.4 kg (20,204 lbs) per year, excluding milk consumed by her calves,[2] whereas the same average value for a single cow in Israel was reported in the Philippine press to be 12,240 kg in 2009.[23] High production cows are more difficult to breed at a two-year interval. Many farms take the view that 24 or even 36 month cycles are more appropriate for this type of cow.[citation needed]

text: Dairy cows may continue to be economically productive for many lactation cycles. In theory a longevity of 10 lactations is possible. The chances of problems arising which may lead to a cow being culled are high, however; the average herd life of US Holstein is today fewer than 3 lactations. This requires more herd replacements to be reared or purchased. Over 90% of all cows are slaughtered for 4 main reasons:

text: Infertility – failure to conceive and reduced milk production.

tag: ul

text: Mastitis – a persistent and potentially fatal mammary gland infection, leading to high somatic cell counts and loss of production.

text: Lameness – persistent foot infection or leg problems causing infertility and loss of production.

text: Production – some animals fail to produce economic levels of milk to justify their feed costs.

text:
Cow longevity is strongly correlated with production levels.[24] Lower production cows live longer than high production cows, but may be less profitable. Cows no longer wanted for milk production are sent to slaughter. Their meat is of relatively low value and is generally used for processed meat. Another factor affecting milk production is the stress the cow is faced with. Psychologists at the University of Leicester, UK, analyzed the musical preference of milk cows and found out that music actually influences the dairy cow's lactation. Calming music can improve milk yield, probably because it reduces stress and relaxes the cows in much the same way as it relaxes humans.
[25]

text: Cow comfort and its effects on milk production[edit]

text: Certain behaviors such as eating, rumination, and lying down can be related to the health of the cow and cow comfort.[26] These behaviors can also be related to the productivity of the cows.[26] Likewise, stress, disease, and discomfort will have a negative effect on the productivity of the dairy cows.[26] Therefore, it can be said that it is in the best interest of the farmer to increase eating, rumination, and lying down and decrease stress, disease, and discomfort to achieve the maximum productivity possible.[26] Also, estrous behaviors such as mounting can be a sign of cow comfort, since if a cow is lame, nutritionally deficient, or are housed in an over crowded barn, the performance of estrous behaviors will be altered.[27]

text: Feeding behaviors are obviously important for the dairy cow, as feeding is how the cow will ingest dry matter, however, the cow must ruminate to fully digest the feed and utilize the nutrients in the feed.[28] Dairy cows with good rumen health will likely be more profitable than cows with poor rumen health, as a healthy rumen will aid in the digestion of nutrients.[26] An increase in the time a cow spends ruminating is associated with the increase in health and an increase in milk production.[26] The productivity of dairy cattle is most efficient when the cattle have a full rumen [29]. Also, the standing action while feeding after milking has been suggested to enhance udder health. The delivery of fresh feed while the cattle are away for milking stimulates the cattle to fed upon return, potentially reducing the prevalence of mastitis as the sphincters have time to close while standing [30] This makes the pattern of feeding directly after being milked an ideal method of increasing the efficiency of the herd.

text: Cows have a high motivation to lie down [28] so farmers should be conscious of this, not only because they have a high motivation to lie down, but also because lying down can increase milk yield.[31] When the lactating dairy cow lies down, blood flow is increased to the mammary gland which in return results in a higher milk yield.[31]

text: To ensure that the dairy cows lie down as much as needed, the stalls must be comfortable.[32] Put very simply, a stall should have a rubber mat, bedding, and be large enough for the cow to lie down and get up comfortably.[32] Signs that the stalls may not be comfortable enough for the cows are the cows are standing, either ruminating or not, instead of lying down, or perching, which is when the cow has its front end in the stall and their back end out of the stall.[32]

text: There are 2 types of housing systems in dairy production, free style housing and tie stall. Free style housing is where the cow is free to walk around and interact with its environment and other members of the herd. Tie stall housing is when the cow is chained to a stantion stall with the milking units and feed coming to them.[33]

text: By-products and Processing[edit]

text: Pasteurization is the process of heating milk to a high enough temperature for a short period of time to kill the microbes in the milk and increase keep time and decrease spoilage time. By killing the microbes, decrease the transmission of infection, and elimination of enzymes the quality of the milk and the shelf life increases. Pasteurization is either completed at 63 °C for 30 minutes or a flash pasteurization is completed for 15 seconds at 72 °C.[34] By-products of milk include butterfat, cream, curds, and whey. Butterfat is the main lipid in milk. The cream contains 18–40% butterfat. The industry can be divided into 2 market territories; fluid milk and industrialized milk such as yogurt, cheeses, and ice cream.[35]

text: Whey protein makes up about 20% of milk’s protein composition and is separated for the casein (80% of milk’s protein make up) during the process of curdling cheese. This protein is commonly used in protein bars, beverages and concentrated powder, due to its high quality amino acid profile. It contains levels of both essential amino acids as well as branched that are above those of soy, meat, and wheat.[36] “Diafiltered” milk is a process of ultrafiltration of the fluid milk to separate lactose and water from the casein and whey proteins. This process allows for more efficiency in cheese making and gives the potential to produce low-carb dairy products. [37]

text: Reproduction[edit]

text: Since the 1950s, artificial insemination (AI) is used at most dairy farms;  these farms may keep no bull.  Artificial insemination uses estrus synchronization to indicate when the cow is going through ovulation and is susceptible to fertilization. Advantages of using AI include its low cost and ease compared to maintaining a bull, ability to select from a large number of bulls, elimination of diseases in the dairy industry, improved genetics and improved animal welfare [38] Rather than a large bull jumping on a smaller heifer or weaker cow, AI allows the farmer to complete the breeding procedure within 5 minutes with minimum stress placed on the individual female's body. [38]

text: Dairy cattle are polyestrous, meaning they cycle continuously throughout the year. They tend to be on a 21 day estrus cycle, however for management purposes, some operations sync their cows or heifers using synthetic hormones in order to have the ideal time for breeding and later calving. These hormones are short term and are only used when necessary. For example, one common protocol for synchronization involves an injection of GnRH (gonadotrophin releasing hormone). which increases the levels of follicle stimulating hormone and luteinizing hormone in the body. Then, seven days later prostaglandin F2-alpha is injected, followed by another GnRH injection 48 hours later. This protocol causes the animal to ovulate 24 hours later. [39]

text: Estrus is often called standing heat in cattle and refers to the time in their cycle where the female is receptive towards the male. Estrus behaviour can be detected by an experienced stockman. These behaviours can include standing to be mounted, mounting other cows, restlessness, decreased milk production, and decreased feed intake.[40]

text: More recently, embryo transfer has been used to enable the multiplication of progeny from elite cows.  Such cows are given hormone treatments to produce multiple embryos. These are then 'flushed' from the cow's uterus. 7–12 embryos are consequently removed from these donor cows and transferred into other cows who serve as surrogate mothers. The result will be between 3 and 6 calves instead of the normal single, or rarely, twins.

text: Hormone use[edit]

text: Hormone treatments are sometimes given to dairy cows in some countries to increase reproduction and to increase milk production.

text: The hormones are used to produce multiple embryos have to be administered at specific times to dairy cattle to induce ovulation. Frequently, for economic considerations, these drugs are also used to synchronise a group of cows to ovulate simultaneously. The hormones prostaglandin, gonadotropin-releasing hormone, and progesterone are used for this purpose and sold under the brand names Lutalyse, Cystorelin, Estrumate, Estroplan, Factrel, Prostamate, Fertagyl, Insynch, and Ovacyst. They may be administered by injection.[41]

text: About 17% of dairy cows in the United States are injected with Bovine somatotropin, also called recombinant bovine somatotropin (rBST), recombinant bovine growth hormone (rBGH), or artificial growth hormone.[42] The use of this hormone increases milk production from 11%–25%. The U.S. Food and Drug Administration (FDA) has ruled that rBST is harmless to people. The use of rBST is banned in Canada, parts of the European Union, as well as Australia and New Zealand.

text: In Canada, Canadian Dairy farmers have high screening procedures they have to go through every time the milk is retrieved from the farm; if the regulations are not met the milk does not get loaded onto the truck for further processing. There is to be no medication or hormones in the milk for safety reasons [34]

text: Nutrition[edit]

text: Nutrition plays an important role in keeping cattle healthy and strong.[43] Implementing an adequate nutrition program can also improve milk production and reproductive performance. Nutrient requirements may not be the same depending on the animal's age and stage of production.

text: Forages, which refer especially to hay or straw, are the most common type of feed used. Cereal grains, as the main contributors of starch to diets, are important in meeting the energy needs of dairy cattle. Barley is one example of grain that is extensively used around the world. Barley is grown in temperate to subarctic climates, and it is transported to those areas lacking the necessary amounts of grain.  Although variations may occur, in general, barley is an excellent source of balanced amounts of protein, energy, and fiber.[44]

text: Ensuring adequate body fat reserves is essential for cattle to produce milk and also to keep reproductive efficiency. However, if cattle get excessively fat or too thin, they run the risk of developing metabolic problems and may have problems with calving.[45] Scientists have found that a variety of fat supplements can benefit conception rates of lactating dairy cows. Some of these different fats include oleic acids, found in canola oil, animal tallow, and yellow grease; palmitic acid found in granular fats and dry fats; and linolenic acids which are found in cottonseed, safflower, sunflower, and soybean.[46] It is also important to note that proper levels of fat also improve cattle longevity.

text: Using by-products is one way of reducing the normally high feed costs. However, lack of knowledge of their nutritional and economic value limits their use. Although the reduction of costs may be significant, they have to be used carefully because animal may have negative reactions to radical changes in feeds, (e.g. fog fever). Such a change must then be made slowly and with the proper follow up.[47]

text: Pesticide use[edit]

text: A survey of the primary dairy producing areas in the US indicated that 13 percent of lactating animals were treated with insecticides permethrin, pyrethrin, coumaphos, and dichlorvos primarily by daily or every-other-day coat sprays. Workers, particularly in stanchion barns, may be exposed to higher than recommended amounts of these pesticides.[48]

text: Breeds[edit]

text: According to the Purebred Dairy Cattle Association, PDCA, there are 7 major dairy breeds in the United States.  These are: Holstein, Brown Swiss, Guernsey, Ayrshire, Jersey, Red and White, and Milking Shorthorn.[49]

text: Holstein cows either have distinct white and black markings, or distinct red and white markings. Holstein cows are the biggest of all U.S. dairy breeds. A full mature Holstein cow usually weighs around 1,500 pounds (700 kg) and is 58 inches (147 cm) tall at the shoulder. They are known for their outstanding milk production among the main breeds of dairy cattle. An average Holstein cow produces around 23,000 pounds (10,000 kg) of milk each lactation. Of the 9 million dairy cows in the U.S., approximately 90% of them are of the Holstein descent.[50] The top breed of dairy cow within Canada's national herd category is Holstein, taking up 93% of the dairy cow population, have a production rate of 10,257 kilograms (22,613 lb) of milk per cow that contains 3.9% butter fat and 3.2% protein[4]

text: Brown Swiss cows are widely accepted as the oldest dairy cattle breed, originally coming from a part of northeastern Switzerland. Some experts think that the modern Brown Swiss skeleton is similar to one found that looks to be from around the year 4000 B.C. Also, there is evidence that monks started breeding these cows about 1000 years ago.[51]

text: The Ayrshire breed first originated in the County of Ayr in Scotland. It became regarded as a well established breed in 1812. The different breeds that were crossed to form the Ayrshire are not exactly known. However, there is evidence that several breeds were crossed with the native cattle to create the breed.[52]

text: Guernsey cows originated just off the coast of France on the small Isle of Guernsey. The breed was first known as a separate breed around 1700. Guernseys are known for their ability to produce very high quality milk from grass. Also, the term "Golden Guernsey" is very common as Guernsey cattle produce rich, yellow milk rather than the standard white milk other cow breeds produce.[53]

text: The Jersey breed of dairy cow originated on a small island located off the coast of France called Jersey.[54] Despite being one of the oldest breeds of dairy cattle they now only occupy 4% of the Canadian National Herd[55]. Purebred Jersey cows, according to available data, have been in the UK area since about the year 1741. When they were first bred in this area, they were not known as Jerseys, but rather as the related Alderneys. The period between 1860 and around 1914 was a popular time for Jerseys. In this time span, many countries other than the United States started importing this breed, including Canada, South Africa, and New Zealand, among others.[56]

text: Among the smallest of the dairy breeds, the average Jersey cow matures at approximately 900 pounds (410 kg), with a typical weight range between 800 and 1,200 pounds (360–540 kg). According to North Dakota State University, the fat content of the Jersey cow's milk is 4.9 percent. It is also the highest in protein, at 3.8 percent.[57] This high fat content means the milk is often used for making ice cream and cheeses. According to the American Jersey Cattle Association, Jerseys are found on 20 percent of all US dairy farms and are the primary breed in about 4 percent of dairies.[citation needed]

text: Amongst the Bos indicus, the most popular dairy breed in the world is Sahiwal of the Indian subcontinent. It does not give as much milk as the Taurine breeds, but it is by far the most suitable breed for warmer climates. Australian Friesian Sahiwal and Australian Milking Zebu have been developed in Australia using Sahiwal genetics. Gir, another of the Bos Indicus breeds, has been improved in Brazil for its milk production and is widely used there for dairy.

text: Animal welfare[edit]

text: Animal welfare refers to both the physical and mental state of an animal, and how it is coping with its situation. An animal is considered in a good state of welfare if it is able to express its innate behaviour, comfortable, healthy, safe, well nourished, and is not suffering from negative states such as distress, fear and pain. Good animal welfare requires disease prevention and veterinary treatment, appropriate shelter, management, nutrition, and humane handling. If the animal is slaughtered then it is no longer "good animal welfare".[58] It is the human responsibility of the animals' wellbeing in all husbandry and management practices including humane euthanasia. Welfare differs greatly compared to animal rights. Welfare approves animal use by humans, wheres animal rights do not believe in the use of animals in any circumstance including companion animals.[59]

text: Proper animal handling, or stockmanship, is crucial to dairy animals' welfare as well as the safety of their handlers. Improper handling techniques can stress cattle leading to impaired production and health, such as increased slipping injuries. Additionally, the majority of nonfatal worker injuries on a dairy farm are from interactions with cattle. Dairy animals are handled on a daily basis for a wide variety of purposes including health-related management practices and movement from freestalls to the milking parlor. Due to the prevalence of human-animal interactions on dairy farms, researchers, veterinarians, and farmers alike have focused on furthering our understanding of stockmanship and educating agriculture workers. Stockmanship is a complex concept that involves the timing, positioning, speed, direction of movement, and sounds and touch of the handler.[citation needed]

text:
A recent survey of Minnesota dairy farms revealed that 42.6% of workers learned stockmanship techniques from a family members, and 29.9% had participated in stockmanship training. However, as the growing U.S. dairy industry increasingly relies on an immigrant workforce, stockmanship training and education resources will become more pertinent. Clearly communicating and managing a large culturally diverse workforce brings new challenges such as language barriers and time limitations.[60]
Organizations like the Upper Midwest Agriculture Safety and Health Center (UMASH) offer resources such as bilingual training videos, fact sheets, and informational posters for dairy worker training. Additionally the Beef Quality Assurance Program offer seminars, live demonstrations, and online resources for stockmanship training.

text: In order for the cows to reach high performance in milk yields and reproduction, they must be in great condition and comfortable in the system of which they are reared. Once an individual’s welfare is reduced, so does her efficiency and production. This creates more cost and time on the operation, therefore most farmers strive to create a healthy, hygienic, atmosphere for their cattle. As well as provide quality nutrition that will keep the cows yield high.[61]

text: The practice of dairy production in a factory farm environment has been criticized by animal rights activists. Some of the ethical reasons regarding dairy production cited include how often the dairy cattle are impregnated, the separation of calves from their mothers, and the fact that the cows are considered "spent" and culled at a relatively young age, as well as environmental concerns regarding dairy production.

text: The production of milk requires that the cow be in lactation, which is a result of the cow having given birth to a calf. The cycle of insemination, pregnancy, parturition, and lactation is followed by a "dry" period of about two months before calving, which allows udder tissue to regenerate. A dry period that falls outside this time frames can result in decreased milk production in subsequent lactation.[62]  Dairy operations therefore include both the production of milk and the production of calves. Bull calves are either castrated and raised as steers for beef production or veal.

text: Animal rights groups such as Mercy for Animals also raise welfare concerns by citing undercover footage showing abusive practices at factory farms.[63]


document_title: The Lego Ninjago Movie

question_text: when does the lego ninjago movie take place

text: The Lego Ninjago Movie

text: Plot[edit]

text: A young boy ventures into an old relic shop, where he meets the mysterious owner, Mr. Liu, who begins to tell the boy the legend of Ninjago.

text: Ninjago is a city in the Lego Universe that is frequently attacked by the evil Lord Garmadon, who is the father of Lloyd Garmadon and husband of Koko. Ninjago despises Lloyd for being Lord Garmadon's son, which puts Lloyd under emotional stress. They do not know that Lloyd is part of the secret ninja force, consisting of Nya, Zane, Jay, Cole, Kai and their master named Master Wu who always stop Garmadon from taking over the city. On Lloyd's birthday, Garmadon attacks the city once again only to be defeated. He escapes and fires the Shark Army for failing to help him. He then begins to plan a big attack to conquer Ninjago, and decides to build a gigantic mech that is immune to weapons.

text: Meanwhile, Lloyd and his friends see the return of Master Wu, back from his long trip. Master Wu tells them they aren't real ninjas if they use only mechs and machines. He discusses with Lloyd that his element is green, confusing Lloyd. Master Wu tells Lloyd he must not be angry at Garmadon; he must use his mind to fight. Wu mentions an Ultimate Weapon, giving Lloyd the hope of defeating Garmadon once and for all, despite being forbidden to use the weapon.

text: The next day Garmadon attacks the city with his giant mech and defeats Lloyd. As Garmadon declares his rule over Ninjago, Lloyd returns with the Ultimate Weapon. He fires it, revealing it to be a laser that attracts a real-life cat named Meowthra. Meowthra starts destroying the city while trying to get the laser. Garmadon points the laser to make the cat destroy the other mechs, before Lloyd breaks it. As Garmadon celebrates his victory, Lloyd reveals that he is the Green Ninja, and tells Garmadon that he wishes he wasn't his father, leaving Garmadon confused.

text: Lloyd meets up with his friends and Master Wu, who are all upset with him for using the weapon. Wu tells them they must use an Ultimate, Ultimate Weapon to stop Meowthra from destroying the city, which they would reach by crossing the Forest of Dangers, the Canyon of Death, and the Temple of Fragile Foundations. Garmadon overhears Wu talking about the weapon and follows close behind. He meets up with Wu and fights him, only to end up in a cage, defeated. However, Wu loses his balance and falls off a bridge into a river, telling Lloyd he must use inner peace before getting swept away.

text: The ninjas decide to continue on, with Garmadon leading them much to Lloyd's disappointment. They are caught by the Shark Army, who want revenge. The ninjas try to fight, but are easily defeated. They retreat leaving Lloyd and Garmadon behind to be caught by the Shark Army. The Shark Army begin to fire Lloyd and Garmadon into a volcano. However, the rest of the ninjas save the day using stealth fighting. They all work together with Garmadon to escape the angry Shark Army by building a makeshift helicopter, and Lloyd and Garmadon bond together in the process.

text: They eventually crash down onto the Temple of Fragile Foundations. Garmadon reveals that it is his home, as well as Koko formerly being a ninja warrior herself. He reveals to Lloyd that he wishes he had stayed with him and his mom after deciding to conquer Ninjago, but he couldn't change so he had to stay behind. The ninjas find the Ultimate Ultimate Weapon, consisting of a set of trinkets, only to have it stolen by Garmadon who still wants to take over the city. He wants Lloyd to be his general, but Lloyd rejects his offer. Out of fury, Garmadon locks all of them in the temple as it begins to collapse. Lloyd realizes that inner peace means for them to unleash their power within, and they successfully do this, escaping from the collapsing temple. As they fall of a cliff, Wu saves them with his ship, and they head towards Ninjago.

text: Garmadon arrives and tries to control Meowthra with the weapons but Meowthra eats Garmadon instead. Lloyd and the crew arrive and begin fighting Garmadon's army. As Lloyd approaches Meowthra, he reveals to everyone that he is the green ninja, and realizes that green means life, which brings everything together. He comforts Meowthra and tells Garmadon he forgives him and that he's sorry. Garmadon cries tears of fire, which causes Meowthra to spit him out. After reconciling, Garmadon moves in with Lloyd and Koko, Meowthra becomes the mascot of Ninjago, and Lloyd is hailed as a hero.

text: As the story concludes, Mr. Liu tells the boy that he will start to train him as a ninja.

text: A mid-credits scene also shows a gag reel of a cup stunt performed by Chan as Liu at the film's opening.

text: Cast[edit]

text:
Dave Franco as Lloyd Garmadon,[9] the Green Ninja, leader of the Secret Ninja Force, Lord Garmadon and Misako's son, and Master Wu's nephew.
Michael Peña as Kai,[9] the hotheaded, red Ninja of Fire and Nya's brother.
Kumail Nanjiani as Jay,[9] the quiet and cautious, blue Ninja of Lightning.
Abbi Jacobson as Nya,[9] the strong, silver Ninja of Water, Kai's sister, and Jay's crush.
Zach Woods as Zane,[9] the robotic, white Ninja of Ice.
Fred Armisen as Cole,[9] the laid-back, music-loving black Ninja of Earth.
Jackie Chan as Master Wu,[9] the wisecracking leader of the group, Lord Garmadon's brother and Lloyd's uncle. He also plays Mr. Liu, an elderly shopkeeper who appears in the live-action part of the film to explain the story of Ninjago to a young boy, played by Kaan Guldur.
Justin Theroux as Lord Garmadon,[1] the Dark Ninja, an evil warlord, the father of Lloyd, the ex-husband of Misako and the brother of Master Wu.
Olivia Munn as Misako "Koko",[1] Lord Garmadon's ex-wife and Lloyd's mother. She was formerly known as the legendary "Lady Iron Dragon".
Randall Park as Chen the Cheerleader
Retta as Maggie the Cheerleader
Constance Wu as the Mayor of Ninjago
Charlyne Yi as Terri, an IT Nerd.
Vanara Taing as Asimov, an IT Nerd.
Chris Hardwick as Radio DJ
Robin Roberts as herself, a Lego caricature of the newscaster. In the UK version, she is replaced by Kate Garraway.[10]
Michael Strahan as himself, a Lego caricature of the known media personality and former New York Giants member. In the UK version, he is replaced by Ben Shephard.
David Burrows as Fuchsia Ninja
Alex Kauffman as Ninja Computer
Ali Wong as General Olivia, the fish-themed general of Garmadon's Shark Army.
Todd Hansen as General Omar, the shark-themed general of Garmadon's Shark Army.
Doug Nicholas as General Jollty, the general of Garmadon's Shark Army.
Bobby Lee as Pilates Studios Owner
Laura Kightlinger as Mrs. Laudita
Pearl and Ruby as Meowthra, a live-action cat that terrorizes Ninjago.

text: Development[edit]

text: On September 17, 2013, Warner Bros. announced that it was developing an animated Ninjago film based on the Lego toy line Lego Ninjago. The Hageman brothers, who wrote Lego Ninjago: Masters of Spinjitzu show and co-wrote the story of The Lego Movie, would write the adaptation.[11] Charlie Bean was announced as director, and The Lego Movie team of Dan Lin, Roy Lee, and Phil Lord and Chris Miller as producers.[11] On June 27, 2016, the film's voice cast was announced, including Dave Franco, Michael Peña, Kumail Nanjiani, Zach Woods, Fred Armisen, Jackie Chan, and Abbi Jacobson.[9] Additional voice cast included Justin Theroux as Lord Garmadon and Olivia Munn as Koko.[1]

text: Filming[edit]

text: In order to give the film a more believable father-son atmosphere, Dave Franco and Justin Theroux recorded most of their lines where their characters interact with each other together in a single recording studio. During the process, Franco openly admitted he found himself uncontrollably crying while recording some of his lines. Franco stated "I found myself getting caught up in the moment and basically crying harder than I have in any live-action movie I’ve ever been in".[12][13]

text: Jackie Chan choreographed all of Master Wu's fight scenes in live action before they were recreated in animation for the film. Chan found the experience new to him as well as interesting. “Everything the stunt team does, the ninjas do also”. Chan commented.[14]

text: Soundtrack[edit]

text: Mark Mothersbaugh, who composed the score for The Lego Movie, returned to score The Lego Ninjago Movie.[2]

text:
The Lego Ninjago Movie: Original Motion Picture Soundtrack

Soundtrack album by Mark Mothersbaugh, various artists

Released
September 15, 2017

Recorded
2017
Trackdown Studios (Sydney)

Genre
Film soundtrack, film score

Length
60:09

Label
WaterTower Music

Producer
Mark Mothersbaugh, Shawn Patterson, Bartholomew

Mark Mothersbaugh chronology

Brad's Status
(2017)Brad's Status2017
The Lego Ninjago Movie
(2017)
Thor: Ragnarok
(2017)Thor: Ragnarok2017

Singles from The Lego Ninjago Movie: Original Motion Picture Soundtrack

"Heroes"
Released: September 15, 2017

tag: table

text: Release[edit]

text: The Lego Ninjago Movie was released by Warner Bros. Pictures on September 22, 2017, in 2D, 3D and IMAX 3D.[15] It was originally scheduled for a September 23, 2016 release.[16] A short film, The Master, that promoted the feature film was shown in front of screenings of Storks, which took the original September 23 release date.[17] On February 8, 2017, the first trailer was released. The trailer was shown in front of screenings of The Lego Batman Movie. On July 22, 2017, a second trailer for the film was shown as part of San Diego Comic-Con and released on YouTube later in the day.[18] Both trailers feature the song "Bad Blood" by Taylor Swift, with the second trailer also featuring "It Must Have Been Love" by Roxette, "Ain't Gonna Die Tonight" by Macklemore and "I Wanna Go Out" by American Authors.

text: Marketing[edit]

text: A video game by TT Fusion based on the film, The Lego Ninjago Movie Video Game, was released on September 22, 2017, for Windows PC, Nintendo Switch, PlayStation 4 and Xbox One.[19][20] The game is similar to previous Lego games, with some new features such as multiplayer and new techniques.[19]

text: Reception[edit]

text: Box office[edit]

text: As of November 6, 2017[update], The Lego Ninjago Movie has grossed $57.6 million in the United States and Canada, and $61.7 million in other territories, for a worldwide total of $119.3 million.[7]

text: In North America, the film was released alongside Kingsman: The Golden Circle and Friend Request. Various tracking services had the film projected to gross anywhere from $27–44 million from 4,047 theaters in its opening weekend.[21][22] However, after making $5.8 million on its first day, weekend projections were lowered to $21 million. It ended up debuting to $21.2 million, finishing third at the box office and ranking as the lowest opening of the Lego franchise by over 50%.[6]

text: Critical response[edit]

text: The Lego Ninjago Movie received mixed reviews from critics. On review aggregator website Rotten Tomatoes, the film has an approval rating of 53% based on 112 reviews, with an average rating of 5.8/10. The site's critical consensus reads, "Despite ample charm and a few solid gags, The Lego Ninjago Movie suggests this franchise's formula isn't clicking like it used to."[23] On Metacritic, the film has a weighted average score of 55 out of 100, based on 33 critics, indicating "mixed or average reviews".[24] Audiences polled by CinemaScore gave the film an average grade of "B+" on an A+ to F scale.[6]