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One day there was two little girl's born. She used to be like any original baby
: ''For alternate meanings, see [[Lightning (disambiguation)]].''
'''Lightning''' is a powerful natural [[electrostatic discharge]] produced during a [[thunderstorm]]. This abrupt electric discharge is accompanied by the emission of visible [[light]] and other forms of [[electromagnetic radiation]]. The [[electric current]] passing through the discharge channels rapidly heats and expands the air into [[Plasma (physics)|plasma]], producing acoustic shock waves ([[thunder]]) in the atmosphere.

[[Image:Lightning in Arlington.jpg|thumb|right|258px|Lightning over [[Pentagon City, Virginia|Pentagon City]] in [[Arlington County, Virginia]]]]
== Early lightning research ==
[[Image:Lightning02.jpg|250px|thumb|right|258px|Cloud to cloud lightning]]

During early investigations into electricity via [[Leyden jar]]s and other instruments, a number of people (Dr. Wall, Dr. John Gray, and [[Abbé Nollet]]) proposed that small-scale sparks shared some similarity with lightning.

[[Benjamin Franklin]], who also invented the [[lightning rod]], endeavoured to test this theory using a spire which was being erected in [[Philadelphia]]. Whilst he was waiting for the spire completion, some others ([[Thomas Francois D'Alibard]] and [[De Lors]]) conducted at Marly in [[France]] what became known as the Philadelphia experiments that Franklin had suggested in his book.

Franklin usually gets the credit, as he was the first to suggest this experiment. The Franklin experiment is as follows:

''Whilst waiting for completion of the spire, he got the idea of using a flying object, such as a [[kite flying|kite]], instead. During the next [[thunderstorm]], which was in June 1752, he raised a kite, accompanied by his son as an assistant. On his end of the string he attached a key and tied it to a post with a [[silk]] thread. As time passed, Franklin noticed the loose fibers on the string stretching out; he then brought his hand close to the key and a spark jumped the gap. The rain which had fallen during the storm had soaked the line and made it conductive.''

However, in his autobiography (written 1771-1788, first published 1790), Franklin clearly states that he performed this experiment after those in France, which occurred weeks before his own experiment, without his prior knowledge as of 1752.

As news of the experiment and its particulars spread, the experiment was met with attempts at replication. However, experiments involving lightning are always risky and frequently fatal. The most well-known death during the spate of Franklin imitators was that of Professor [[Georg Richmann]], of [[Saint Petersburg, Russia]]. He had created a set-up similar to Franklin's, and was attending a meeting of the Academy of Sciences when he heard [[thunder]]. He ran home with his engraver to capture the event for posterity. While the experiment was underway, [[ball lightning]] appeared, collided with Richmann's head, and killed him, leaving a red spot. His shoes were blown open, parts of his clothes singed, the engraver knocked out, the doorframe of the room split, and the door itself torn off its hinges.

== Modern research ==
[[Image:Lightning simulator questacon05.jpg|thumb|250px|A [[Tesla coil]] creating small "leaders" at Questacon, Canberra]]

Although experiments from the time of Franklin showed that lightning was a discharge of static electricity, there was little improvement in theoretical understanding of lightning (in particular how it was generated) for more than 150 years. The impetus for new research was from the field of [[power engineering]]: [[Electric power transmission|power transmission lines]] came into use, and engineers needed to know much more about lightning. Although ''causes'' were debated (and are today to some extent), research produced a wealth of new information about lightning phenomena, especially amounts of current and energy involved.
The following picture emerged:

An initial discharge, (or path of ionised air), called a "[[step_leader|stepped leader]]", starts from the [[thundercloud]] and proceeds generally downward in a number of quick jumps, typical length 50 meters, but taking a relatively long time (200 milliseconds) to reach the ground. This initial phase involves a small [[electric current]] and is almost invisible compared to the later effects. When the downward leader is quite close, a small discharge comes up from a grounded (usually tall) object because of the intensified electric field.

Once the ground discharge meets the stepped leader, the circuit is closed, and the main stroke follows with much higher current. The main stroke travels at about 0.1 [[Speed of light|''c'']] (100 million feet per second) and has high current for 100 microseconds or so. It may persist for longer periods with lower current.

In addition, lightning often contains a number of restrikes, separated by a much larger amount of time, 30 milliseconds being a typical value. This rapid restrike effect was probably known in antiquity, and the "[[strobe light]]" effect is often quite noticeable.

Positive lightning does not generally fit the above pattern.

== How it is formed ==
[[Image:Double_Lightning_in_Glyfada-Athens.jpg|left|thumb|300px|Double lightning. An extremely rarely captured phenomenon.]]

The first process in the generation of lightning is the forcible separation of positive and negative [[charge carrier]]s within a cloud or air. The mechanism by which this happens is still the subject of research, but one widely accepted theory is the polarisation mechanism. This mechanism has two components: the first is that falling droplets of ice and rain become electrically polarised as they fall through the atmosphere's natural electric field, and the second is that colliding ice particles become charged by [[electrostatic induction]]. Once charged, by whatever mechanism, work is performed as the opposite charges are driven apart and energy is stored in the [[electric field]]s between them. The positively charged crystals tend to rise to the top, causing the cloud top to build up a positive charge, and the negatively charged crystals and [[hail]]stones drop to the middle and bottom layers of the cloud, building up a negative charge. Cloud-to-cloud lightning can appear at this point. Cloud-to-ground lightning is less common. [[Cumulonimbus cloud|Cumulonimbus]] clouds that do not produce enough ice crystals usually fail to produce enough charge separation to cause lightning.

When sufficient negatives and positives gather in this way, and when the [[electric field]] becomes sufficiently strong, an [[spark gap|electrical discharge]] occurs within the clouds or between the clouds and the ground, producing the ''bolt''. It has been suggested by experimental evidence that these discharges are triggered by [[cosmic ray]] strikes which ionise atoms, releasing electrons that are accelerated by the electric fields, ionising other air molecules and making the air conductive by a [[runaway breakdown]], then starting a lightning strike. During the strike, successive portions of air become conductive as the electrons and positive ions of air molecules are pulled away from each other and forced to flow in opposite directions (stepped channels called [[Step leader|step leaders]]). The conductive filament grows in length. At the same time, electrical energy stored in the electric field flows radially inward into the conductive filament.

When a charged step leader is near the ground, opposite charges appear on the ground and enhance the electric field. The electric field is higher on trees and tall buildings. If the electric field is strong enough, a discharge can initiate from the ground. This discharge starts as [[positive streamer]] and, if it develops as a positive leader, can eventually connect to the descending discharge from the cloud.

Lightning can also occur within the ash clouds from [[volcano|volcanic eruptions]]{{ref|usgs_hvo}}<sup>,</sup>{{ref|noaa_galgunggung}}, or can be caused by violent [[forest fire]]s which generate sufficient dust to create a [[static charge]].

[[Image:Lightning hits tree - NOAA.jpg|right|thumb|Negative C-G lightning with two visible non-connected streamers]]
A bolt of lightning usually begins when an invisible negatively-charged [[stepped leader]] stroke is sent out from the cloud. As it does so, a positively charged ''streamer'' is usually sent out from the positively charged ground or cloud. When the two leaders meet, the electric current greatly increases. The region of high current propagates back up the positive stepped leader into the cloud. This "return stroke" is the most luminous part of the strike, and is the part that is really visible. Most lightning strikes usually last about a quarter of a second. Sometimes several strokes will travel up and down the same leader strike, causing a flickering effect. This discharge rapidly [[superheating|superheats]] the leader channel, causing the air to expand rapidly and produce a [[shock wave]] heard as thunder.

It is possible for streamers to be sent out from several different objects simultaneously, with only one connecting with the leader and forming the discharge path. Photographs have been taken on which non-connected streamers are visible such as that shown on the right.

This type of lightning is known as '''negative lightning''' because of the discharge of negative charge from the cloud, and accounts for over 95% of all lightning.

An average bolt of ''negative'' lightning carries a current of 30 [[ampere|kiloamperes]], transfers a charge of 5 [[coulomb]]s, has a potential difference of about 100 [[volt|megavolts]] and dissipates 500 [[joule|megajoules]] (enough to
light a 100 [[watt]] lightbulb for 2 months).

Positive lightning makes up less than 5 % of all lightning. It occurs when the ''[[stepped leader]]'' forms at the positively charged cloud tops, with the consequence that a negatively charged ''streamer'' issues from the ground. The overall effect is a discharge of positive charges to the ground. Research carried out after the discovery of positive lightning in the 1970s showed that positive lightning bolts are typically six to ten times more powerful than negative bolts, last around ten times longer, and can strike several kilometers or miles distant from the clouds. During a positive lightning strike, huge quantities of [[extremely low frequency|ELF]] and [[very low frequency|VLF]] [[radio wave]]s are generated.

As a result of their power, positive lightning strikes are considerably more dangerous. At the present time, [[aircraft]] are not designed to withstand such strikes, since their existence was unknown at the time standards were set, and the dangers unappreciated until the destruction of a [[glider]] in 1999 [http://web.archive.org/web/20041009230137/http://www.dft.gov.uk/stellent/groups/dft_avsafety/documents/page/dft_avsafety_500699.hcsp].

Positive lightning is also now believed to have been responsible for the [[1963]] in-flight explosion and subsequent crash of [[Pan Am Flight 214]], a [[Boeing 707]]. Subsequently, aircraft operating in U.S. airspace have been required to have lightning discharge wicks to reduce the chances of a similar occurrence.

Positive lightning has also been shown to trigger the occurrence of [[#Sprites, elves, jets and other upper atmospheric lightning|upper atmospheric lightning]]. It tends to occur more frequently in [[winter storm]]s and at the end of a [[thunderstorm]].

An average bolt of ''positive'' lightning carries a current of 300 kiloamperes (about ten times as much current as a bolt of negative lightning), transfers a charge of up to 300 [[coulomb]]s, has a potential difference up to 1 gigavolt (a thousand million volts), dissipates enough energy to light a 100 [[watt]] lightbulb for up to 95 years, and lasts for tens or hundreds of milliseconds.

[[Image:Lightning cloud to cloud (aka).jpg|thumb|Intracloud or possibly cloud-to-cloud lightning.]]
[[Heinz Kasemir]] first hypothesised that a lightning leader system actually develops in a '''bipolar''' fashion, with both a positive and a negative branching leader system connected at the system origin and containing a net zero charge. This process provides a means for the positive leader to conduct away the net negative charge collected during development, allowing the leader system to act as an extending polarised conductor. Such a polarised conductor would be able to maintain intense [[electric field]]s at its ends, supporting continued leader development in weak-background electric fields.

During the eighties, flight tests showed that [[aircraft]] can trigger a bipolar [[stepped leader]] when crossing charged cloud areas. Many scientists think that positive and negative lightning in a cloud are actually bipolar lightning.

To spontaneously [[ionise]] air and conduct electricity across it, an [[electric field]] of [[field strength]] of approximately 2500 kilovolts per metre is required. However, measurements inside storm clouds to date have failed to locate fields this strong, with typical fields being between 100 and 400 kilovolts per metre. While there remains a possibility that researchers are failing to encounter the small high-strength regions of the large clouds, the odds of this are diminishing as further measurements continue to fall short.

A theory by [[Alex Gurevich]] of the [[Lebedev Physical Institute]] in 1992 proposes that [[cosmic ray]]s may provide the beginnings of what he called a '''[[runaway breakdown]]'''. Cosmic rays strike an air molecule and release extremely energetic electrons having enhanced mean free paths of tens of centimeters. These strike other air molecules, releasing more electrons which are accelerated by the storm's electric field, forming a [[electron avalanche|chain reaction]] of long-trajectory electrons and creating a conductive [[Plasma (physics)|plasma]] many tens of meters in length. This was initially considered a fringe theory, but is now becoming [[mainstream]] because of the lack of other theories.

It has been recently revealed that most lightning emits an intense burst of [[X-rays]] and/or [[gamma ray|gamma-rays]] which seem to be produced during the stepped-leader and dart-leader phases just before the stroke becomes visible. The X-ray bursts typically have a total duration of less than 100 microseconds and have energies extending up to nearly a few hundred [[keV]]. The presence of these high-energy events match and support the "runaway breakdown" theory, and were discovered through the examination of rocket-triggered lightning, and from [[satellite]] monitoring of natural lightning.

[[NASA]]'s [[RHESSI]] satellite typically reports 50 gamma-ray events per day, and many of these are strong enough to fit the theory. Additionally, [[Radio frequency|low-frequency radio emissions]] detected at ground level can detect lightning bolts from upwards of 4000 km away; combining these with gamma-ray burst events detected from above show overlapping positions and timing.

There are problems with the "runaway breakdown" theory, however. While there seems to be a strong correlation between gamma-ray events and lightning, there are insufficient events detected to account for the amount of lightning occurring across the planet. Another issue is the amount of energy the theory states is required to initiate the breakdown. Cosmic rays of sufficient energy strike the atmosphere on average only once per 50 seconds per square kilometre. Measured X-ray burst intensity also falls short, with results indicating particle energy 1/20th of the theory's value.

== Types of lightning ==
Some lightning strikes take on particular characteristics, and scientists and the public have given names to these various types of lightning.

=== Intracloud lightning, sheet lightning, anvil crawlers ===
Intracloud lightning is the most common type of lightning which occurs completely inside one cumulonimbus cloud, and is commonly called an anvil crawler. Discharges of electricity in anvil crawlers travel up the sides of the [[cumulonimbus cloud]] branching out at the anvil top.

=== Cloud-to-ground lightning, anvil-to-ground lightning ===
[[Image:Lightning over Oradea Romania 2.jpg|thumb|right|258px|Lightning over [[Oradea]] in [[Romania]]]]
[[Image:LightningToronto.jpg|thumb|250px|right|Lightning strike]]
Cloud-to-ground lightning is a great lightning discharge between a cumulonimbus cloud and the ground initiated by the downward-moving leader stroke. This is the second most common type of lightning. One special type of cloud-to-ground lightning is anvil-to-ground lightning, a form of positive lightning, since it emanates from the anvil top of a cumulonimbus cloud where the ice crystals are positively charged. In anvil-to-ground lightning, the leader stroke issues forth in a nearly horizontal direction till it veers toward the ground. These usually occur miles ahead of the main storm and will strike without warning on a sunny day. They are signs of an approaching storm and are known colloquially as "bolts from the blue".

=== Bead lightning, ribbon lightning, staccato lightning ===
Another special type of cloud-to-ground lightning is bead lightning. This is a regular cloud-to-ground stroke that contains a higher intensity of luminosity. When the discharge fades it leaves behind a ''string of beads'' effect for a brief moment in the leader channel. A third special type of cloud-to-ground lightning is ribbon lightning. These occur in thunderstorms where there are high cross winds and multiple return strokes. The winds will blow each successive return stroke slightly to one side of the previous return stoke, causing a ribbon effect. The last special type of cloud-to-ground lightning is staccato lightning, which is nothing more than a leader stroke with only one return stroke.

=== Cloud-to-cloud lightning ===
Cloud-to-cloud or intercloud lightning is a somewhat rare type of discharge lightning between two or more completely separate cumulonimbus clouds.

=== Cloud-to-ground lightning ===
Cloud-to-ground lightning is a lightning discharge between the ground and a cumulonimbus cloud from an upward-moving leader stroke. These thunderstorm clouds are formed wherever there is enough upward motion, instability in the vertical, and moisture to produce a deep cloud that reaches up to levels somewhat colder than freezing. These conditions are most often met in summer. Lightning occurs less frequently in the winter because there is not as much instability and moisture in the atmosphere as there is in the summer. These two ingredients work together to make convective storms that can produce lightning. Without instability and moisture, strong thunderstorms are unlikely. Lightning originates around 15,000 to 25,000 feet above sea level when raindrops are carried upward until some of them convert to ice. For reasons that are not widely agreed upon, a cloud-to-ground lightning flash originates in this mixed water and ice region. The charge then moves downward in 50 yard sections called step leaders. It keeps moving toward the ground in these steps and produces a channel along which charge is deposited. Eventually it encounters something on the ground that is a good connection. The circuit is complete at that time, and the charge is lowered from cloud-to-ground. The return stroke is a flow of charge(current) which produces luminosity much brighter than the part that came down. This entire event usually takes less than half a second.

=== Heat lightning''' or '''summer lightning ===
Heat lightning (or, in the UK, "summer lightning") is nothing more than the faint flashes of lightning on the [[horizon]] from distant thunderstorms. Heat lightning was named because it often occurs on hot summer nights. Heat lightning can be an early warning sign that thunderstorms are approaching. In [[Florida]], heat lightning is often seen out over the water at night, the remnants of storms that formed during the day along a [[seabreeze]] [[cold front|front]] coming in from the opposite coast.

Some cases of "heat lightning" can be explained by the [[refraction]] of sound by bodies of air with different [[density|densities]]. An observer may see nearby lightning, but the sound from the discharge is refracted over his head by a change in the temperature, and therefore the density, of the air around him. As a result, the lightning discharge appears to be silent. [http://whyfiles.org/137lightning/index.html]

=== Ball lightning ===
{{main|Ball lightning}}
Ball lightning is described as a floating, illuminated ''ball'' that occurs during thunderstorms. They can be fast moving, slow moving or nearly stationary. Some make hissing or crackling noises or no noise at all. Some have been known to pass through windows and even dissipate with a bang. Ball lightning has been described by [[eyewitness]]es but rarely, if ever, recorded by [[meteorologist]]s.

The engineer [[Nikola Tesla]] wrote, "I have succeeded in determining the mode of their formation and producing them artificially" (''Electrical World and Engineer'', 5 March 1904). There is some speculation that [[electrical breakdown]] and [[arcing]] of [[cotton]] and [[gutta-percha]] wire insulation used by Tesla may have been a contributing factor, since some theories of ball lightning require the involvement of carbonaceous materials. Some later [[experiment]]ers have been able to briefly produce small luminous balls by igniting carbon-containing materials atop sparking [[Tesla Coil]]s.

Several theories have been advanced to describe ball lightning, with none being universally accepted. Any complete theory of ball lightning must be able to describe the wide range of reported properties, such as those described in Singer's book "The Nature of Ball Lightning" and also more contemporary research. Japanese research shows that ball lightning has been seen several times without any connection to stormy weather or lightning.

Ball lightning field properties are more extensive than realised by many scientists not working in this field. The typical fireball diameter is usually standardised as 20&ndash;30 cm, but ball lightning several meters in diameter has been reported (Singer). A recent photograph by a [[Queensland]] ranger, Brett Porter, showed a fireball that was estimated to be 100 meters in diameter. The photograph has appeared in the scientific journal ''Transactions of the Royal Society''. The object was a glowing globular zone (the breakdown zone?) with a long, twisting, rope-like projection (the funnel?).

Fireballs have been seen in tornadoes, and they have also split apart into two or more separate balls and recombined. Fireballs have carved trenches in the [[peat]] [[swamps]] in [[Ireland]]. Vertically linked fireballs have been reported. One theory that may account for this wider spectrum of observational evidence is the idea of [[combustion]] inside the low-velocity region of axisymmetric (spherical) [[vortex]] breakdown of a natural vortex (e.g., the '[[Hill's spherical vortex]]'). The scientist Coleman was the first to propose this theory in 1993 in ''Weather'', a publication of the [[Royal Meteorological Society]].

Ball lightning is hardly ever seen. In fact, there are only a few pictures of it.

[[St Elmo's fire]] was correctly identified by Franklin as electrical in nature. It is not the same as [[ball lightning]].

=== Sprites, elves, jets, and other upper atmospheric lightning ===
Reports by scientists of strange lightning phenomena above storms date back to at least 1886. However, it is only in recent years that fuller investigations have been made. This has sometimes been called ''megalightning''.

''Sprites'' are now well-documented electrical discharges that occur high above the [[cumulonimbus]] cloud of an active [[thunderstorm]]. They appear as luminous reddish-orange, [[neon]]-like flashes, last longer than normal lower stratospheric discharges (typically around 17 milliseconds), and are usually spawned by discharges of positive lightning between the cloud and the ground. Sprites can occur up to 50 km from the location of the lightning strike, and with a time delay of up to 100 milliseconds. Sprites usually occur in clusters of two or more simultaneous vertical discharges, typically extending from 65 to 75 km (40 to 47 miles) above the earth, with or without less intense filaments reaching above and below. Sprites are preceded by a ''sprite halo'' that forms because of heating and [[ionisation]] less than 1 millisecond before the sprite. Sprites were first photographed on July 6, 1989, by scientists from the [[University of Minnesota]] and named after the mischievous sprites in the plays of [[Shakespeare]].

Recent research [http://www.uh.edu/admin/media/nr/102002/beringsprites100702.html] carried out at the [[University of Houston]] in 2002 indicates that some normal (negative) lightning discharges produce a ''sprite halo'', the precursor of a sprite, and that ''every'' lightning bolt between cloud and ground attempts to produce a sprite or a sprite halo. Research in 2004 by scientists from [[Tohoku University]] found that [[very low frequency]] emissions occur at the same time as the sprite, indicating that a discharge within the cloud may generate the sprites [http://dx.doi.org/10.1029/2004GL021943].

''Blue jets'' differ from sprites in that they project from the top of the cumulonimbus above a thunderstorm, typically in a narrow cone, to the lowest levels of the [[ionosphere]] 40 to 50 km (25 to 30 miles) above the earth. They are also brighter than sprites and, as implied by their name, are blue in colour. They were first recorded on [[October 21]], [[1989]], on a video taken from the [[space shuttle]] as it passed over Australia.

''Elves'' often appear as a dim, flattened, expanding glow around 400 km (250 miles) in diameter that lasts for, typically, just one millisecond [http://hbar.stanford.edu/cpbl/elves]. They occur in the ionosphere 100 km (60 miles) above the ground over thunderstorms. Their colour was a puzzle for some time, but is now believed to be a red hue. Elves were first recorded on another shuttle mission, this time recorded off [[French Guiana]] on [[October 7]], [[1990]]. [[Elves]] is a frivolous [[acronym]] for ''E''missions of ''L''ight and ''V''ery Low Frequency Perturbations From ''E''lectromagnetic Pulse ''S''ources. This refers to the process by which the light is generated; the excitation of [[nitrogen]] molecules due to [[electron]] collisions (the electrons having been energised by the electromagnetic pulse caused by a positive lightning bolt).

On [[September 14]], [[2001]], scientists at the [[Arecibo Observatory]] photographed a huge jet double the height of those previously observed, reaching around 80 km (50 miles) into the atmosphere. The jet was located above a thunderstorm over the ocean, and lasted under a second. Lightning was initially observed travelling up at around 50,000 m/s in a similar way to a typical ''blue jet'', but then divided in two and sped at 250,000 m/s to the ionosphere, where they spread out in a bright burst of light.

On [[July 22]], [[2002]], five gigantic jets between 60 and 70 km (35 to 45 miles) in length were observed over the [[South China Sea]] from [[Taiwan]], reported in ''Nature'' [http://sprite.phys.ncku.edu.tw/new/news/0626_presss/nature01759_r.pdf]. The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots.

Researchers have speculated that such forms of upper atmospheric lightning may play a role in the formation of the [[ozone layer]].

=== Streak lightning ===
Most of all lightning is streak lightning. This is nothing more than the return stroke, the visible part of the lightning stroke. Because most of these strokes occur inside a cloud, we do not see many of the individual return strokes in a thunderstorm.

=== Triggered lightning ===
Lightning has been triggered directly by human activity in several instances. Lightning struck the [[Apollo 12]] soon after takeoff, and has struck soon after thermonuclear explosions. It has also been triggered by launching rockets carrying spools of wire into thunderstorms. The wire unwinds as the rocket climbs, making a convenient path for the lightning to use. These bolts are typically very straight [http://skydiary.com/gallery/chase2002/2002lightmovie.html].

=== Lightning throughout the Solar System ===
Lightning requires the electrical breakdown of gas, so lightning cannot exist in the [[vacuum]] of space. However, lightning has been observed within the [[Celestial body atmosphere|atmosphere]]s of other [[planets]], such as [[Venus]] and [[Jupiter]]. Lightning on Jupiter is estimated to be 100 times as powerful, but fifteen times less frequent, than that which occurs on Earth. Lightning on [[Venus (planet)|Venus]] is still a controversial subject after decades of study. During the Soviet [[Venera]] and U.S. [[Pioneer program|Pioneer]] missions of the '70s and '80s, signals suggesting lightning may be present in the upper atmosphere were detected [http://www-ssc.igpp.ucla.edu/~strange/JATP_paper/JATP_title.html]. However, recently the [[Cassini-Huygens]] mission fly-by of Venus detected no signs of lightning at all.

== Lightning safety ==
{{main|Lightning safety}}
[[Image:Lightning animation.gif|thumb|right|350px|animation of a lightning strike]]
[[Thunderstorm]]s are the primary source of lightning. Because people have been struck many kilometers away from a storm, seeking immediate and effective shelter when thunderstorms approach is an important part of lightning safety.
Contrary to popular notion, there is no 'safe' location outdoors. People have been struck in sheds, makeshift shelters, etc. A better location would be inside a vehicle (a crude type of [[Faraday cage]]).
It is advisable to keep appendages away from any attached metallic components once inside (keys in ignition, etc.).

Several different types of devices, including [[lightning rod]]s, [[lightning arrester]]s, and [[electrical charge dissipater]]s, are used to prevent lightning damage and safely redirect lightning strikes.

Nearly 2000 persons per year in the world are injured by lightning strikes, and between 25 to 33 % of those struck die. Lightning [[injury|injuries]] result from three factors: electrical damage, intense heat, and the mechanical energy which these generate. While sudden death is common because of the huge voltage of a lightning strike, survivors often fare better than victims of other electrical injuries caused by a more prolonged application of lesser voltage.

Lightning can incapacitate humans in 4 different ways:

* Direct strike
* 'Splash' from nearby objects struck
* Ground strike near victim
* [[EMP]] or electromagnetic pulse from close proximity strikes - especially during positive lightning discharges

In a ''direct hit'' the [[electrical charge]] strikes the victim first. Counterintuitively, if the victim's skin [[electrical resistance|resistance]] is high enough, much of the current will ''flash'' around the skin or clothing to the ground, resulting in a surprisingly benign outcome.
''Splash'' hits occur when lightning effectively bounces off a nearby object and strikes the victim en route to ground.
''Ground'' strikes, in which the bolt lands near the victim and is conducted through the victim via his or her connection to the ground (such as through the feet), can cause great damage.

The most critical injuries are to the [[circulatory system]], the [[lung]]s, and the [[central nervous system]]. Many victims suffer immediate [[cardiac arrest]] and will not survive without prompt emergency care, which is safe to administer because the victim will not retain any [[electrical charge]] after the lightning has struck (of course, the helper could be struck by a separate bolt of lightning in the vicinity). Others incur [[myocardial infarction]] and various [[cardiac arrhythmias]], either of which can be rapidly fatal as well. The intense heat generated by a lightning strike can cause lung damage, and the chest can be damaged by the mechanical force of rapidly expanding heated air. Either the electrical or the mechanical force can result in loss of consciousness, which is very common immediately after a strike. [[Amnesia]] and [[confusion]] of varying duration often result as well. A complete physical examination by [[paramedic]]s or [[physician]]s may reveal ruptured [[eardrum]]s, and ocular [[cataract]]s may develop, sometimes more than a year after an otherwise uneventful recovery.

The lightning often leaves skin burns in characteristic [[Lichtenberg figure]]s, sometimes called ''lightning flowers''; they may persist for hours or days, and are a useful indicator for medical examiners when trying to determine the cause of death. They are thought to be caused by the rupture of small [[capillaries]] under the skin, either from the current or from the [[shock wave]]. It is also speculated that the [[electromagnetic pulse|EMP]] created by a nearby lightning strike can cause [[cardiac arrest]].

There is sometimes spectacular and unconventional lightning damage. ''Hot lightning'' which lasts for more than a second can deposit immense energy, melting or [[carbonization|carbonizing]] large objects. One such example is the destruction of the basement [[insulator]] of the 250-metre-high central [[radio mast|mast]] of [[longwave transmitter Orlunda]], which led to its collapse.

== Facts and trivia ==
[[Image:Lightning scar 0009.jpg|thumb|250px|Old lightning scar ([[Georgetown, South Carolina]])]]
A bolt of lightning can reach [[temperature]]s approaching 28,000 [[kelvin]]s (50,000 degrees [[Fahrenheit]]) in a split second. This is about five times hotter than the surface of the [[sun]]. The heat of lightning which strikes loose soil or sandy regions of the ground may fuse the soil or sand into glass channels called [[fulgurite]]s. These are sometimes found under the [[sand]]y surfaces of [[beach]]es and [[golf course]]s, or in [[desert]] regions. Fulgurites are evidence that lightning spreads out into branching channels when it strikes the ground.

[[Tree]]s are frequent [[Conductor (material)|conductors]] of lightning to the ground ([http://www.erh.noaa.gov/er/lwx/lightning/lgtng-hits-tree.jpg photo of a tree being struck by lightning]<!--NB, although this is an NOAA url, as far as I can tell, this is not an NOAA photo and so may not be public domain, hence external link-->). Since [[Sap (plant)|sap]] is a poor conductor, its [[electrical resistance]] causes it to be heated [[steam explosion|explosively]] into [[steam]], which blows off the [[bark]] outside the lightning's path. In following seasons trees overgrow the damaged area and may cover it completely, leaving only a vertical scar. If the damage is severe, the tree may not be able to recover, and [[decay]] sets in, eventually killing the tree. Occasionally, a tree may explode completely, as in this [[Giant Sequoia]] struck in [[Geneva]] [http://www.pinetum.org/lightning.htm]. It is commonly thought that a tree standing alone is more frequently struck, though in some [[forested]] areas, lightning scars can be seen on almost every tree.

Of all common [[tree]]s the most frequently struck is the [[oak]]. It has a deep central [[root]] that goes beneath the tree, as well as hollow water-filled cells that run up and down the wood of the oak's trunk. These two qualities make oak trees better grounded and more conductive than trees with shallow roots and closed cells.

*The odds of an average person living in the USA being struck by lightning once in his lifetime has been estimated to be 1:3000.

*The city of [[Teresina]] in northern [[Brazil]] has the third-highest rate of occurrences of lightning strikes in the world. The surrounding region is referred to as the ''Chapada do Corisco'' ("Flash Lightning Flatlands").

*The [[United States]] is home to "Lightning Alley", a group of states in the American Southeast that collectively see more lightning strikes per year than any other place in the US. The most notable state in Lightning Alley is [[Florida]].

*The saying "lightning never strikes twice in the same place" is false. The [[Empire State Building]] is struck by lightning on average 100 times each year, and was once struck 15 times in 15 minutes.

*[[Ukraine|Ukrainian]] President [[Viktor Yushchenko]] is probably the highest-ranked modern statesman to be struck by lightning (which happened in [[2005]] with no reported health consequences)

*[[Jim Caviezel]], the actor who played Jesus in the film ''[[The Passion of the Christ]]'', is reported to have been struck by lightning during shooting. The assistant director [[Jan Michelini]] was struck twice [http://news.bbc.co.uk/2/hi/entertainment/3209223.stm].

*Golfers [[Retief Goosen]] and [[Lee Trevino]] have both been struck by lightning while playing [http://www.golfeurope.com/almanac/players/trevino.htm].

*Although commonly associated with thunderstorms, lightning strikes can occur on any day, even in the absence of clouds.

*Lightning interferes with AM ([[amplitude modulation]]) radio signals much more than FM ([[frequency modulation]]) signals, providing an easy way to gauge local lightning strike intensity.

In [[Film|movie]]s and [[comics|comic]]s of the contemporary U.S. and many other countries, lightning is often employed as an ominous, dramatic sign. It may herald a waking of a great [[evil]] or emergence of a [[crisis]]. This has often also been spoofed, with the uttering of certain words or phrases causing flashes of lightning to appear outside of windows (and often scaring or disturbing some characters). While this is usually typical of [[cartoon|cartoons]], it has also been employed by regular [[Television program|TV shows]] and [[Film|movies]]. Various [[novel]]s and [[Role-playing game|role playing game]]s with [[fantasy]] tint involves wizardry of lightning bolt, weapon embodying the power of lightning, etc. The [[comic book]] character Billy Batson changed into the [[superhero]] [[Captain Marvel (DC Comics)|Captain Marvel]] by saying the word "Shazam!", which called down a bolt of magic lightning to make the change. [[Flash (comics)| Flash]] II ([[Barry Allen]]) and III ([[Wally West]]) were both granted their superspeed in accidents involving lightning.

The bolt of lightning in [[heraldry]] is distinguished from the [[lightning bolt]] and is shown as a zigzag with non-pointed ends. It is also distinguished from the "fork of lightning". The lightning bolt shape was a [[symbol]] of male humans among the [[Native Americans in the United States|Native Americans]] such as the [[Apache]] (a [[rhombus]] shape being a symbol for females) in the [[American Old West]].

The name of New Zealand / Australia's most celebrated [[thoroughbred]] horse, [[Phar Lap]], derives from the shared [[Zhuang]] and [[Thai]] word for lightning.

Estimating distance of a lightning strike:
The flash of a lightning strike and resulting thunder occur at roughly the same time. But light travels at 186,000 miles in a second, almost a million times the speed of sound. Sound travels at the slower speed of one-fifth of a mile in the same time. So the flash of lightning is seen before thunder is heard. By counting the seconds between the flash and the thunder and dividing by 5, you can estimate your distance from the strike (in miles).

== See also ==
*[[List of light sources]]
*[[List of people who became famous for surviving a deadly event]]

{{Met_vars}}

== References ==
*{{cite journal | author=Alex Larsen | title=Photographing Lightning With a Moving Camera | journal=Annual Report Smithsonian Institute | year=1905 | volume=60 | issue=1 | pages=119-127}}
*{{cite journal | author=Anna Gosline | title=Thunderbolts from space | journal=[[New Scientist]] | year=May 2005 | volume=186 | issue=2498 | pages=30-34}}
*Martin Uman, Dover Press(2006)

== External links ==
{{commons|Lightning}}
*[http://www.phy6.org/stargaze/Svandgrf.htm#q1 Lightning] &mdash; Explains how the energy of lightning results from an interplay of updrafts and gravity, acting somewhat like the Van de Graaff generator.
*[http://www.newscientist.com/channel/fundamentals/mg18624981.200 How cosmic rays trigger lightning strikes]
*[http://science.howstuffworks.com/lightning.htm Article from How Stuff Works]
*[http://www.airhive.net/modules.php?op=modload&name=4nAlbum&file=index&do=showpic&pid=11&orderby=dateD Video: Lightning protection for an Antenna]
*[http://groups.yahoo.com/group/LightningProtection The only Internet technical & general interest forum about lightning safety and power quality.] The forum provides scientifically accurate information on Power Quality, lightning safety, keraunic medicine, surge protection, UPSs, manufacturers' spurious performance claims & specifications, junk science debunked, etc. Moderated by scientists and engineers.
*dmoz: [http://dmoz.org/Science/Earth_Sciences/Meteorology/Weather_Phenomena/Thunderstorms_and_Lightning/ Thunderstorms and Lightning]
*[http://www.lightningsafety.noaa.gov/ams_lightning_rec.htm Lightning Safety Page - National Weather Service Pueblo Colorado] Citat: "...This is known as a "side flash". Many people who are "struck" by lightning are not hit directly by the main lightning channel, but are affected by the side flash..."
*[http://home.earthlink.net/~jimlux/lfacts.htm Lightning Facts]
*[http://www.esdjournal.com/articles/lightn.htm Laser Beam Triggers Lightning Strike During Japanese Experiment]
*[http://www.crh.noaa.gov/pub/ltg.html Colorado Lightning Resource Center]
*[http://web.archive.org/web/20020624044704/http&#58;//www.sandia.gov/LabNews/LN04-25-97/lightning_story.html Webarchive: April 25,1997 Sandia-led research may zap old beliefs about lightning protection at critical facilities;] Triggered lightning tests leading to safer storage bunkers
*[http://www.sciencedaily.com/releases/2003/11/031106051013.htm 2003-11-06, ScienceDaily: Thunderstorm Research Shocks Conventional Theories; Florida Tech Physicist Throws Open Debate On Lightning's Cause]
*[http://www.aldis.at Austrian Lightning Detection and Information System]
*[http://www.euclid.org European Cooperation for Lightning Detection]
*[http://www.uscoles.com/howtolightn.htm How to Photograph Lightning] A page with both brief and verbose instructions on taking lightning photos.
*[http://www.onera.fr/dmph-en/foudre/foudroiement.html Lightning strike to aircraft]
*{{note|usgs_hvo}} [http://hvo.wr.usgs.gov/volcanowatch/1998/98_06_11.html USGS, Hawaii Observation] Account of ash lightning. See 5th paragraph.
*{{note|noaa_galgunggung}} [http://www.ngdc.noaa.gov/seg/hazard/stratoguide/galunfeat.html Teachers Guide to Stratovolcanoes of the World, Galgunggung, Indonesia]
*[http://www.macro-photo.org/photo-gallery/lightning-thunderstorm-albuquerque-photo-images-of-nature.htm Nature Photography - Images of Lightnings]
*[http://www.bindaz.com/harishpalaniappan/blog/archives/2005/09/lightning_and_e.html Lightning and The Empire State Building NYC]
*[http://www.flickr.com/groups/storms/pool/ Lightning Gallery] Flickr set of lightning from around the world
*[http://205.243.100.155/frames/longarc.htm#Pos-Lightning1 Positive Lightning Strike] Photo of a nearby positive lightning strike that nearly kills the Australian photographer
*[http://www.uspln.com/ United States Precision Lightning Network] - Live lightning data map

=== Jets, sprites & elves ===
*[http://www.uh.edu/admin/media/nr/archives99/0399/lightning.html March 2, 1999, University of Houston: UH Physicists Pursue Lightning-Like Mysteries] Quote: "...Red sprites and blue jets are brief but powerful lightning-like flashes that appear at altitudes of 40-100 km (25-60 miles) above thunderstorms..."
**[http://www.uh.edu/research/spg/Sprites99.html Ground and Balloon-Borne Observations of Sprites and Jets]
* Barrington-Leigh, C. P., "''[http://sprg.ssl.berkeley.edu/~cpbl/elves/ Elves] : Ionospheric Heating By the Electromagnetic Pulses from Lightning (A primer)''". Space Science Lab, Berkeley.
* "''[http://www.physics.otago.ac.nz/space/darwin97/darwin97.html Darwin Sprites '97]''". Space Physics Group, University of Otago.
* Gibbs, W. Wayt, "''[http://www-star.stanford.edu/~vlf/optical/press/elves97sciam/ Sprites and Elves : Lightning's strange cousins flicker faster than light itself]''". San Francisco. ScientificAmerican.com.
* Barrington-Leigh, Christopher, "''[http://www-star.stanford.edu/~vlf/Antarctica/Palmer/ VLF Research at Palmer Station]''".
*[http://www.nature.com/news/2005/050321/full/050321-6.html Heavenly light show caught on film (Nature)] - Requires subscription to news@nature.com.
*[http://www.wetterchronik.de/english/unwetter20050603.htm Lucky snapshot: lightning strikes chemical mill in Germany]

[[Category:Lightnings| ]]
[[Category:Space plasmas]]
[[Category:Weather hazards]]

[[ca:Llamp]]
[[cs:Blesk]]
[[da:Lyn]]
[[de:Blitz]]
[[es:Rayo]]
[[fr:Foudre]]
[[he:ברק (תופעה מטאורולוגית)]]
[[hu:Villám]]
[[id:Kilat]]
[[io:Fulmino]]
[[it:Fulmine]]
[[ja:雷]]
[[ko:번개]]
[[ku:Brûsk]]
[[nl:Bliksem]]
[[no:Lyn (naturfenomen)]]
[[pl:Błyskawica]]
[[ru:Молния]]
[[sl:Strela]]
[[tr:Yıldırım]]
[[zh:闪电]]

Revision as of 23:29, 25 April 2006

             One day there was two little girl's born. She used to be like any original baby
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