Lightning
Overview
 
Lightning is an atmospheric
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 electrostatic discharge
Electrostatic discharge
Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...

 (spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...

) accompanied by thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

, which typically occurs during thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

s, and sometimes during volcanic eruptions
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 or dust storm
Dust storm
A dust / sand storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Particles are transported by saltation and suspension, causing soil to move from one place and deposition...

s. From this discharge of atmospheric electricity
Atmospheric electricity
Atmospheric electricity is the regular diurnal variations of the Earth's atmospheric electromagnetic network . The Earth's surface, the ionosphere, and the atmosphere is known as the global atmospheric electrical circuit...

, a leader of a bolt of lightning can travel at speeds of 220000 km/h (136,701.7 mph), and can reach temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

s approaching 30000 °C (54,032 °F), hot enough to fuse silica sand into glass channels known as fulgurite
Fulgurite
Fulgurites are natural hollow glass tubes formed in quartzose sand, or silica, or soil by lightning strikes. They are formed when lightning with a temperature of at least instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product...

s, which are normally hollow and can extend some distance into the ground.
Encyclopedia
Lightning is an atmospheric
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

 electrostatic discharge
Electrostatic discharge
Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...

 (spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...

) accompanied by thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

, which typically occurs during thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

s, and sometimes during volcanic eruptions
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 or dust storm
Dust storm
A dust / sand storm is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Particles are transported by saltation and suspension, causing soil to move from one place and deposition...

s. From this discharge of atmospheric electricity
Atmospheric electricity
Atmospheric electricity is the regular diurnal variations of the Earth's atmospheric electromagnetic network . The Earth's surface, the ionosphere, and the atmosphere is known as the global atmospheric electrical circuit...

, a leader of a bolt of lightning can travel at speeds of 220000 km/h (136,701.7 mph), and can reach temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

s approaching 30000 °C (54,032 °F), hot enough to fuse silica sand into glass channels known as fulgurite
Fulgurite
Fulgurites are natural hollow glass tubes formed in quartzose sand, or silica, or soil by lightning strikes. They are formed when lightning with a temperature of at least instantaneously melts silica on a conductive surface and fuses grains together; the fulgurite tube is the cooled product...

s, which are normally hollow and can extend some distance into the ground. There are some 16 million lightning storms
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

 in the world every year. Lightning causes ionisation in the air through which it travels, leading to the formation of nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...

 and ultimately, nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...

, of benefit to plant life below.

Lightning can also occur within the ash clouds from volcanic eruptions
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

, or can be caused by violent forest fires
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

 which generate sufficient dust to create a static charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

.

How lightning initially forms is still a matter of debate. Scientists have studied root causes ranging from atmospheric perturbations (wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

, humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

, friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

, and atmospheric pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...

) to the impact of solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...

 and accumulation of charged solar particles. Ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 inside a cloud is thought to be a key element in lightning development, and may cause a forcible separation of positive and negative charges
Charge carrier
In physics, a charge carrier is a free particle carrying an electric charge, especially the particles that carry electric currents in electrical conductors. Examples are electrons and ions...

 within the cloud, thus assisting in the formation of lightning.

The irrational fear of lightning (and thunder) is astraphobia
Astraphobia
Astraphobia, also known as astrapophobia, brontophobia, keraunophobia, or tonitrophobia, is an abnormal fear of thunder and lightning, a type of specific phobia. It is a treatable phobia that both humans and animals can develop. The term astraphobia derives from the Greek words ἀστραπή and φόβος...

. The study or science of lightning is called fulminology, and someone who studies lightning is referred to as a fulminologist.

History of lightning research

Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

 (1706–1790) endeavored to test the theory that sparks shared some similarity with lightning by using a spire which was being erected in Philadelphia, United States. While waiting for completion of the spire, he got the idea to use a flying object such as a kite. During the next thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

, which was in June 1752, it was reported that he raised a kite. He was accompanied by his son as an assistant. On his end of the string he attached a key, and he tied it to a post with a silk
Silk
Silk is a natural protein fiber, some forms of which can be woven into textiles. The best-known type of silk is obtained from the cocoons of the larvae of the mulberry silkworm Bombyx mori reared in captivity...

 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.

Franklin was not the first to perform the kite experiment. Thomas-François Dalibard
Thomas-François Dalibard
Thomas-François Dalibard was born in Crannes-en-Champagne, France in 1709 and died in 1799.-Relationship with Ben Franklin:He first met U.S. scientist Benjamin Franklin in 1767 during one of Franklin's visits to France and it is said that they became friends.In 1750, Benjamin Franklin published a...

 and De Lors conducted it at Marly-la-Ville in France, a few weeks before Franklin's experiment. 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, others attempted to replicate it. However, experiments involving lightning are always risky and frequently fatal. One of the most well-known deaths during the spate of Franklin imitators was that of Professor Georg Richmann of Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...

, Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

. He created a set-up similar to Franklin's, and was attending a meeting of the Academy of Sciences when he heard thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

. He ran home with his engraver to capture the event for posterity. According to reports, while the experiment was under way, ball lightning
Ball lightning
Ball lightning is an unexplained atmospheric electrical phenomenon. The term refers to reports of luminous, usually spherical objects which vary from pea-sized to several metres in diameter. It is usually associated with thunderstorms, but lasts considerably longer than the split-second flash of a...

 appeared and collided with Richmann's head, killing him.

Although experiments from the time of Benjamin Franklin showed that lightning was a discharge of static electricity
Electrostatics
Electrostatics is the branch of physics that deals with the phenomena and properties of stationary or slow-moving electric charges....

, 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 came from the field of power engineering
Power engineering
Power engineering, also called power systems engineering, is a subfield of engineering that deals with the generation, transmission and distribution of electric power as well as the electrical devices connected to such systems including generators, motors and transformers...

: as power transmission lines
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...

 came into service, engineers needed to know much more about lightning in order to adequately protect lines and equipment. In 1900, Nikola Tesla
Nikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

 generated artificial lightning by using a large Tesla coil
Tesla coil
A Tesla coil is a type of resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high voltage, low current, high frequency alternating current electricity. Tesla coils produce higher current than the other source of high voltage discharges, electrostatic machines...

, enabling the generation of enormously high voltages sufficient to create lightning.

Properties

Lightning can occur with both positive and negative polarity. An average bolt of negative
Electrical polarity
Electrical polarity is present in every electrical circuit. Electrons flow from the negative pole to the positive pole. In a direct current circuit, one pole is always negative, the other pole is always positive and the electrons flow in one direction only...

 lightning carries an electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 of 30,000 ampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

s (30 kA), and transfers fifteen coulombs of electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 and 500 megajoules
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...

 of energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...

. Large bolts of lightning can carry up to 120 kA and 350 coulombs. An average bolt of positive lightning carries an electric current of about 300 kA — about 10 times that of negative lightning.

The voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...

 involved for both is proportional
Proportionality (mathematics)
In mathematics, two variable quantities are proportional if one of them is always the product of the other and a constant quantity, called the coefficient of proportionality or proportionality constant. In other words, are proportional if the ratio \tfrac yx is constant. We also say that one...

 to the length of the bolt. However, lightning leader development is not just a matter of the electrical breakdown
Electrical breakdown
The term electrical breakdown or electric breakdown has several similar but distinctly different meanings. For example, the term can apply to the failure of an electric circuit....

 of air, which occurs at a voltage gradient of about 1 megavolts per metre (MV/m). The ambient electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

s required for lightning leader propagation can be one or two orders of magnitude (10−2) less than the electrical breakdown strength. The potential
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...

 ("volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...

age") gradient
Gradient
In vector calculus, the gradient of a scalar field is a vector field that points in the direction of the greatest rate of increase of the scalar field, and whose magnitude is the greatest rate of change....

 inside a well-developed return-stroke channel is on the order of hundreds of volts per metre (V/m) due to intense channel ionization
Ionization
Ionization is the process of converting an atom or molecule into an ion by adding or removing charged particles such as electrons or other ions. This is often confused with dissociation. A substance may dissociate without necessarily producing ions. As an example, the molecules of table sugar...

, resulting in a true power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...

 output on the order of one megawatt per meter (MW/m) for a vigorous return stroke current of 100 kA. The average peak power output of a single lightning stroke is about one trillion watts — one terawatt (1012 W), and the stroke lasts for about 30 millionths of a second — 30 microseconds.

Lightning rapidly heats the air in its immediate vicinity to about 20,000 °C
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

 (36,000 °F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...

) — about three times the temperature of the surface of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

. The sudden heating effect and the expansion of heated air gives rise to a supersonic
Supersonic
Supersonic speed is a rate of travel of an object that exceeds the speed of sound . For objects traveling in dry air of a temperature of 20 °C this speed is approximately 343 m/s, 1,125 ft/s, 768 mph or 1,235 km/h. Speeds greater than five times the speed of sound are often...

 shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 in the surrounding clear air. It is this shock wave, once it decays to an acoustic
Acoustics
Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...

 wave, that is heard as thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

.

The return stroke of a lightning bolt follows a charge channel about a centimetre (0.4 in) wide.

Different locations have different potentials and currents for an average lightning strike. In the United States, for example, Florida experiences the largest number of recorded strikes in a given period during the summer season , has very sandy soils in some areas, and electrically conductive water-saturated soils in others. As much of Florida lies on a peninsula, it is bordered by the ocean on three sides. The result is the daily development of sea and lake breeze boundaries that collide and produce thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

s.

NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 scientists have found that electromagnetic radiation
Electromagnetic radiation
Electromagnetic radiation is a form of energy that exhibits wave-like behavior as it travels through space...

 created by lightning in clouds only a few miles high can create a safe zone in the Van Allen radiation belt
Van Allen radiation belt
The Van Allen radiation belt is a torus of energetic charged particles around Earth, which is held in place by Earth's magnetic field. It is believed that most of the particles that form the belts come from solar wind, and other particles by cosmic rays. It is named after its discoverer, James...

s that surround the earth. This zone, known as the "Van Allen Belt slot", may be a safe haven for satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s in middle Earth orbits
Medium Earth Orbit
Medium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....

 (MEOs), protecting them from the Sun's intense radiation.

Formation

Positive lightning (a rarer form of lightning that originates from positively charged regions of the thundercloud) does not generally fit the preceding pattern.

Cloud particle collision hypothesis

According to this cloud particle charging hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...

, charges are separated when ice crystals rebound off graupel. Charge separation appears to require strong updrafts which carry water droplets upward, supercooling
Supercooling
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....

 them to between -10 and -40 °C. These water droplets collide with ice crystals to form a soft ice-water mixture called graupel. Collisions between ice crystals and graupel pellets usually results in positive charge being transferred to the ice crystals, and negative charge to the graupel. Updrafts drive the less heavy ice crystals upwards, causing the cloud top to accumulate increasing positive charge. Gravity causes the heavier negatively charged graupel to fall toward the middle and lower portions of the cloud, building up an increasing negative charge. Charge separation and accumulation continue until the electrical potential
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...

 becomes sufficient to initiate a lightning discharge, which occurs when the distribution of positive and negative charges forms a sufficiently strong electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

.

Polarization mechanism hypothesis

The mechanism by which charge separation happens is still the subject of research. Another hypothesis is the polarization mechanism, which has two components:
  1. Falling droplets of ice and rain become electrically polarized as they fall through the Earth's natural electric field;
  2. Colliding/rebounding cloud particles become oppositely charged.


There are several hypotheses for the origin of charge separation.

Lightning initiation

Even assuming an electric field has been established, the mechanism by which the lightning discharge begins is not well known. Electric field measurements in thunderclouds are typically not large enough to directly initiate a discharge. Many hypotheses have been proposed, ranging from including runaway breakdown
Runaway breakdown
Runaway breakdown is a theory of lightning initiation proposed by Alex Gurevich in 1992.Electrons in air have a mean free path of ~1cm. Fast electrons which move at a large fraction of the speed of light have a mean free path up to 100 times longer...

 to locally enhanced electric fields near elongated water droplets or ice crystals. Percolation theory
Percolation theory
In mathematics, percolation theory describes the behavior of connected clusters in a random graph. The applications of percolation theory to materials science and other domains are discussed in the article percolation.-Introduction:...

, especially for the case of biased percolation, describe random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes.

Leader formation and the return stroke

As a thundercloud moves over the surface of the Earth, an electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...

 equal to but opposite the charge of the base of the thundercloud is induced in the Earth below the cloud. The induced ground charge follows the movement of the cloud, remaining underneath it.

An initial bipolar discharge, or path of ionized air, starts from a negatively charged region of mixed water and ice in the thundercloud. Discharge ionized channels are known as leaders. The positive and negative charged leaders, generally a "stepped leader", proceed in opposite directions. The negatively-charged one proceeds downward in a number of quick jumps (steps). 90 percent of the leaders exceed 45 m (148 ft) in length, with most in the order of 50 to 100 m (164 to 492 feet). As it continues to descend, the stepped leader may branch into a number of paths. The progression of stepped leaders takes a comparatively long time (hundreds of millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....

s) to approach the ground. This initial phase involves a relatively small electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 (tens or hundreds of ampere
Ampere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...

s), and the leader is almost invisible when compared with the subsequent lightning channel.

When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field
Electric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...

. The electric field is strongest on ground-connected 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 conductive discharge (called a positive streamer) can develop from these points. This was first theorized by Heinz Kasemir. As the field increases, the positive streamer may evolve into a hotter, higher current leader which eventually connects to the descending stepped leader from the cloud. It is also possible for many streamers to develop from many different objects simultaneously, with only one connecting with the leader and forming the main discharge path. Photographs have been taken on which non-connected streamers are clearly visible.

Once a channel of ionized air is established between the cloud and ground this becomes a path of least resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...

and allows for a much greater current to propagate from the Earth back up the leader into the cloud. This is the return stroke and it is the most luminous
Luminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...

 and noticeable part of the lightning discharge.

Discharge

When the electric field becomes strong enough, an electrical discharge (the bolt of lightning) occurs within clouds or between clouds and the ground. During the strike, successive portions of air become a conductive discharge channel as the electrons and positive ions of air molecules are pulled away from each other and forced to flow in opposite directions.

The electrical discharge rapidly superheats
Superheating
In physics, superheating is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling...

 the discharge channel, causing the air to expand rapidly and produce a shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 heard as thunder. The rolling and gradually dissipating rumble of thunder is caused by the time delay of sound coming from different portions of a long stroke.

Re-strike

High speed videos (examined frame-by-frame) show that most lightning strikes are made up of multiple individual strokes. A typical strike is made of 3 or 4 strokes, though there may be more.

Each re-strike is separated by a relatively large amount of time, typically 40 to 50 milliseconds. Re-strikes can cause a noticeable "strobe light
Strobe light
A strobe light or stroboscopic lamp, commonly called a strobe, is a device used to produce regular flashes of light. It is one of a number of devices that can be used as a stroboscope...

" effect.

Each successive stroke is preceded by intermediate dart leader strokes akin to, but weaker than, the initial stepped leader. The stroke usually re-uses the discharge channel taken by the previous stroke.

The variations in successive discharges are the result of smaller regions of charge within the cloud being depleted by successive strokes.

The sound of thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

 from a lightning strike is prolonged by successive strokes.

Types

Some lightning strikes exhibit particular characteristics; scientists and the general public have given names to these various types of lightning. The lightning that is most-commonly observed is streak lightning. This is nothing more than the return stroke, the visible part of the lightning stroke. The majority of strokes occur inside a cloud so we do not see most of the individual return strokes during a thunderstorm.

Cloud-to-ground lightning

This is the best known and second most common type of lightning. Of all the different types of lightning, it poses the greatest threat to life and property since it strikes the ground. Cloud-to-ground (CG) lightning is a lightning discharge between a cumulonimbus cloud and the ground. It is initiated by a leader stroke moving down from the cloud.

Bead lightning

Bead lightning is a type of cloud-to-ground lightning which appears to break up into a string of short, bright sections, which last longer than the usual discharge channel. It is relatively rare. Several theories have been proposed to explain it; one is that the observer sees portions of the lightning channel end on, and that these portions appear especially bright. Another is that, in bead lightning, the width of the lightning channel varies; as the lightning channel cools and fades, the wider sections cool more slowly and remain visible longer, appearing as a string of beads.

Ribbon lightning

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.

Staccato lightning

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. These are often found in the visual vault area near the mesocyclone
Mesocyclone
A mesocyclone is a vortex of air, approximately 2 to 10 miles in diameter , within a convective storm....

 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.

Forked lightning

Forked lightning is a name, not in formal usage, for cloud-to-ground lightning that exhibits branching of its path.

Ground-to-cloud lightning

Ground-to-cloud lightning is a lightning discharge between the ground and a cumulonimbus cloud initiated by an upward-moving leader stroke. This type of lightning forms when negatively charged ions called the stepped leader rise up from the ground and meet the positively charged ions in a cumulonimbus cloud. Then the strike goes back to the ground as the return stroke. This is also called positive lightning.

Cloud-to-cloud lightning

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
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...

 within a single cloud it is known as intra-cloud lightning. Intra-cloud lightning is the most frequently occurring type.

These are most common between the upper anvil
Cumulonimbus incus
A cumulonimbus incus is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape...

 portion and lower reaches of a given thunderstorm. This lightning can sometimes be observed at great distances at night as so-called "heat lightning
Heat lightning
Heat lightning is a misnomer for the faint flashes of lightning on the horizon or other clouds from distant thunderstorms that do not have accompanying sounds of thunder. This occurs because the lightning occurs very far away and the sound waves dissipate before they reach the observer...

". In such instances, the observer may see only a flash of light without hearing any thunder. The "heat" portion of the term is a folk association between locally experienced warmth and the distant lightning flashes.

Another terminology used for cloud–cloud or cloud–cloud–ground lightning is "Anvil Crawler", due to the habit of the charge typically originating from beneath or within the anvil and scrambling through the upper cloud layers of a thunderstorm, normally generating multiple branch strokes which are dramatic to witnesses. 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.

Sheet lightning

Sheet lightning is an informal name for cloud-to-cloud lightning that exhibits a diffuse brightening of the surface of a cloud, caused by the actual discharge path being hidden. The lightning itself cannot be seen by the spectator, so it appears as only a flash, or a sheet of light.

Heat lightning

Heat lightning is a common name for a lightning flash that appears to produce no thunder
Thunder
Thunder is the sound made by lightning. Depending on the nature of the lightning and distance of the listener, thunder can range from a sharp, loud crack to a long, low rumble . The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within...

 because it occurs too far away for the thunder to be heard. The sound waves dissipate before they reach the observer.

Dry lightning

Dry lightning is a term in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 and the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 for lightning that occurs with no precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

 at the surface. This type of lightning is the most common natural cause of wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...

s. Pyrocumulus cloud
Pyrocumulus cloud
A pyrocumulus, or literally fire cloud, is a dense cumuliform cloud associated with fire or volcanic activity.A pyrocumulus is similar dynamically in some ways to a firestorm, and the two phenomena may occur in conjunction with each other...

s produce lightning for the same reason that it is produced by cumulonimbus clouds. When the higher levels of the atmosphere are cooler, and the surface is warmed to extreme temperatures due to a wildfire, volcano, etc., convection will occur, and the convection produces lightning. Therefore, fire can beget dry lightning through the development of more dry thunderstorms which cause more fires (see positive feedback
Positive feedback
Positive feedback is a process in which the effects of a small disturbance on a system include an increase in the magnitude of the perturbation. That is, A produces more of B which in turn produces more of A. In contrast, a system that responds to a perturbation in a way that reduces its effect is...

).

Rocket lightning

It is a form of cloud discharge, generally horizontal
Horizontal plane
In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...

 and at cloud base, with a luminous channel appearing to advance through the air with visually resolvable speed, often intermittently.

Positive lightning

Unlike the far more common "negative" lightning, positive lightning occurs when a positive charge is carried by the top of the clouds (generally anvil clouds
Cumulonimbus incus
A cumulonimbus incus is a cumulonimbus cloud which has reached the level of stratospheric stability and has formed the characteristic flat, anvil-top shape...

) rather than the ground. Generally, this causes the leader arc to form in the anvil of the cumulonimbus and travel horizontally for several miles before veering down to meet the negatively charged streamer rising from the ground. The bolt can strike anywhere within several miles of the anvil of the thunderstorm, often in areas experiencing clear or only slightly cloudy skies; they are also known as "bolts from the blue" for this reason. Positive lightning makes up less than 5% of all lightning strikes. Because of the much greater distance they must travel before discharging, positive lightning strikes typically carry six to ten times the charge and voltage difference of a negative bolt and last around ten times longer. During a positive lightning strike, huge quantities of ELF
Extremely low frequency
Extremely low frequency is a term used to describe radiation frequencies from 3 to 300 Hz. In atmosphere science, an alternative definition is usually given, from 3 Hz to 3 kHz...

 and VLF
Very low frequency
225px|thumb|right|A VLF receiving antenna at [[Palmer Station]], Antarctica, operated by Stanford UniversityVery low frequency or VLF refers to radio frequencies in the range of 3 kHz to 30 kHz. Since there is not much bandwidth in this band of the radio spectrum, only the very simplest signals...

 radio wave
Radio Wave
Radio Wave may refer to:*Radio frequency*Radio Wave 96.5, a radio station in Blackpool, UK...

s are generated.

As a result of their greater power, as well as lack of warning, positive lightning strikes are considerably more dangerous. At the present time, aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 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
Glider (sailplane)
A glider or sailplane is a type of glider aircraft used in the sport of gliding. Some gliders, known as motor gliders are used for gliding and soaring as well, but have engines which can, in some cases, be used for take-off or for extending a flight...

 in 1999. The standard in force at the time of the crash, Advisory Circular AC 20-53A, was replaced by Advisory Circular AC 20-53B in 2006, however it is unclear whether adequate protection against positive lighting was incorporated.

Positive lightning is also now believed to have been responsible for the 1963 in-flight explosion and subsequent crash of Pan Am Flight 214
Pan Am Flight 214
Pan Am Flight 214, a Boeing 707-121 registered as , was en route from Baltimore to Philadelphia on December 8, 1963, when it crashed near Elkton, Maryland after being hit by lightning, killing all 81 on board.-Flight history:...

, a Boeing 707
Boeing 707
The Boeing 707 is a four-engine narrow-body commercial passenger jet airliner developed by Boeing in the early 1950s. Its name is most commonly pronounced as "Seven Oh Seven". The first airline to operate the 707 was Pan American World Airways, inaugurating the type's first commercial flight on...

. Due to the dangers of lightning, aircraft operating in U.S. airspace have been required to have lightning discharge wicks to reduce the damage by a lightning strike, but these measures may be insufficient for positive lightning.

Positive lightning has also been shown to trigger the occurrence of upper atmosphere lightning. It tends to occur more frequently in winter storm
Winter storm
A winter storm is an event in which the dominant varieties of precipitation are formed that only occur at low temperatures, such as snow or sleet, or a rainstorm where ground temperatures are low enough to allow ice to form...

s, as with thundersnow
Thundersnow
Thundersnow, also known as a winter thunderstorm or a thunder snowstorm, is a relatively rare kind of thunderstorm with snow falling as the primary precipitation instead of rain. It typically falls in regions of strong upward motion within the cold sector of an extratropical cyclone...

, and at the end of a thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

.

Ball lightning

Ball lightning may be an atmospheric electrical
Atmospheric electricity
Atmospheric electricity is the regular diurnal variations of the Earth's atmospheric electromagnetic network . The Earth's surface, the ionosphere, and the atmosphere is known as the global atmospheric electrical circuit...

 phenomenon, the physical nature of which is still controversial. The term refers to reports of luminous
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...

, usually spherical objects which vary from pea-sized to several metres in diameter. 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. 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.

Laboratory experiments have produced effects that are visually similar to reports of ball lightning, but at present, it is unknown whether these are actually related to any naturally occurring phenomenon. One theory is that ball lightning may be created when lightning strikes silicon in soil, a phenomenon which has been duplicated in laboratory testing. Given inconsistencies and the lack of reliable data and completely contradicting and unpredictable behavior, the true nature of ball lightning is still unknown and was often regarded as a fantasy or a hoax
Hoax
A hoax is a deliberately fabricated falsehood made to masquerade as truth. It is distinguishable from errors in observation or judgment, or rumors, urban legends, pseudosciences or April Fools' Day events that are passed along in good faith by believers or as jokes.-Definition:The British...

. Reports of the phenomenon were dismissed for lack of physical evidence, and were often regarded the same way as UFO sightings.
Severely contradicting descriptions of ball lightning makes it impossible even to create plausible hypothesis that will take into account described behavior.

One theory that may account for this wider spectrum of observational evidence is the idea of combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 inside the low-velocity region of spherical vortex
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...

 breakdown of a natural vortex (e.g., the 'Hill's spherical vortex'). Natural ball lightning appears infrequently and unpredictably, and is therefore rarely (if ever truly) photographed. However, several purported photos and videos exist. Perhaps the most famous story of ball lightning unfolded when 18th-century physicist Georg Wilhelm Richmann
Georg Wilhelm Richmann
Georg Wilhelm Richmann was a German physicist who lived in Russia....

 installed a lightning rod
Lightning rod
A lightning rod or lightning conductor is a metal rod or conductor mounted on top of a building and electrically connected to the ground through a wire, to protect the building in the event of lightning...

 in his home and was struck in the head - and killed - by a "pale blue ball of fire."

Upper-atmospheric lightning

Reports by scientists of strange lightning phenomena about 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

Sprites are large-scale electrical discharges that occur high above a thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

 cloud, or cumulonimbus, giving rise to a quite varied range of visual shapes. They are triggered by the discharges of positive lightning between the thundercloud and the ground. The phenomena were named after the mischievous sprite (air spirit) Puck in Shakespeare
William Shakespeare
William Shakespeare was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the "Bard of Avon"...

's A Midsummer Night's Dream
A Midsummer Night's Dream
A Midsummer Night's Dream is a play that was written by William Shakespeare. It is believed to have been written between 1590 and 1596. It portrays the events surrounding the marriage of the Duke of Athens, Theseus, and the Queen of the Amazons, Hippolyta...

. They normally are coloured reddish-orange or greenish-blue, with hanging tendrils below and arcing branches above their location, and can be preceded by a reddish halo. They often occur in clusters, lying 50 kilometres (31.1 mi) to 90 kilometres (55.9 mi) above the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's surface. Sprites were first photographed on July 6, 1989 by scientists from the University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...

 and have since been witnessed tens of thousands of times. Sprites have been mentioned as a possible cause in otherwise unexplained accidents involving high altitude vehicular operations above thunderstorms.

Blue jets

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
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...

 25 miles (40.2 km) to 50 miles (80.5 km) 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
Space Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...

 as it passed over Australia, and subsequently extensively documented in 1994 during aircraft research flights by the University of Alaska.

On September 14, 2001, scientists at the Arecibo Observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...

 photographed a huge jet double the height of those previously observed, reaching around 50 miles (80.5 km) into the atmosphere. The jet was located above a thunderstorm over the ocean, and lasted under a second. Lightning was initially observed traveling 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
South China Sea
The South China Sea is a marginal sea that is part of the Pacific Ocean, encompassing an area from the Singapore and Malacca Straits to the Strait of Taiwan of around...

 from Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...

, reported in Nature. The jets lasted under a second, with shapes likened by the researchers to giant trees and carrots.

Elves

Elves often appear as dim, flattened, circular in the horizontal plane, expanding glows around 250 miles (402.3 km) in diameter that last for, typically, just one millisecond. They occur in the ionosphere 60 miles (96.6 km) above the ground over thunderstorms. Their color 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
French Guiana
French Guiana is an overseas region of France, consisting of a single overseas department located on the northern Atlantic coast of South America. It has borders with two nations, Brazil to the east and south, and Suriname to the west...

 on October 7, 1990. Elves is an acronym for Emissions of Light and Very Low Frequency Perturbations from Electromagnetic Pulse Sources. This refers to the process by which the light is generated; the excitation of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

 molecules due to electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

 collisions (the electrons possibly having been energized by the electromagnetic pulse caused by a discharge from the Ionosphere).

Rocket-triggered

Lightning has been triggered by launching lightning rocket
Lightning rocket
The term lightning rocket can generically describe a rocket device used to trigger lightning as well as a specific system patented by Robert E. Betts....

s carrying spools of wire into thunderstorms. The wire unwinds as the rocket ascends, providing a path for lightning. These bolts are typically very straight due to the path created by the wire.

Lightning has also been triggered directly by other human activities: Flying aircraft can trigger lightning. Furthermore, lightning struck Apollo 12
Apollo 12
Apollo 12 was the sixth manned flight in the American Apollo program and the second to land on the Moon . It was launched on November 14, 1969 from the Kennedy Space Center, Florida, four months after Apollo 11. Mission commander Charles "Pete" Conrad and Lunar Module Pilot Alan L...

 soon after takeoff, and has struck soon after thermonuclear explosions.

Volcanically triggered

There are three types of volcanic lightning
Dirty thunderstorm
A dirty thunderstorm is a weather phenomenon that occurs when lightning is produced in a volcanic plume.A famous image of the phenomenon was photographed by Carlos Gutierrez and occurred in Chile above the Chaiten Volcano. It circulated widely on the internet...

:
  • Extremely large volcanic eruptions, which eject gases and material high into the atmosphere, can trigger lightning. This phenomenon was documented by Pliny The Elder
    Pliny the Elder
    Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

     during the 79 AD eruption of Vesuvius, in which he perished.
  • An intermediate type which comes from a volcano's vents, sometimes 1.8 miles (2.9 km) long.
  • Small spark-type lightning about 3 foot (0.9144 m) long lasting a few milliseconds.

Laser-triggered

Since the 1970s, 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.

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 too short a period 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. 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 channel
Plasma channel
A plasma channel is a conductive channel of plasma. A plasma channel can be formed in these ways:-*With a high-powered laser that operates at a certain frequency that will provide enough energy for an atmospheric gas to break into its ions, or form a plasma, such as in a Laser-Induced Plasma...

s.

Extraterrestrial lightning

Lightning requires the electrical breakdown of a gas, so it cannot exist in a visual form in the vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 of space. However, lightning has been observed within the atmospheres of other planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...

s, such as Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...

, Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 and Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

. Lightning on Venus is still a controversial subject after decades of study. During the Soviet Venera
Venera
The Venera series probes were developed by the Soviet Union between 1961 and 1984 to gather data from Venus, Venera being the Russian name for Venus...

 and U.S. Pioneer
Pioneer program
The Pioneer program is a series of United States unmanned space missions that was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system...

 missions of the 1970s and '80s, signals suggesting lightning may be present in the upper atmosphere were detected. However, recently the Cassini–Huygens mission fly-by of Venus detected no signs of lightning at all. Despite this, it has been suggested that radio pulses recorded by the spacecraft Venus Express
Venus Express
Venus Express is the first Venus exploration mission of the European Space Agency. Launched in November 2005, it arrived at Venus in April 2006 and has been continuously sending back science data from its polar orbit around Venus. Equipped with seven science instruments, the main objective of the...

 may originate from lightning on Venus.

High energy radiation emissions due to lightning

The production of X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...

s by a bolt of lightning was theoretically predicted as early as 1925 but no evidence was found until 2001/2002, when researchers at the New Mexico Institute of Mining and Technology
New Mexico Institute of Mining and Technology
New Mexico Institute of Mining and Technology is a university located in Socorro, New Mexico....

 detected X-ray emissions from an induced lightning strike along a wire trailed behind a rocket shot into a storm cloud. In the same year University of Florida
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...

 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. 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.

Terrestrial gamma-ray flashes

A number of observations by space-based telescopes have revealed even higher energy gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

 emissions, the so-called terrestrial gamma-ray flashes (TGFs). These observations pose a challenge to current theories of lightning, especially with the discovery of the clear signatures of antimatter
Antimatter
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...

 produced in lightning.

It has been discovered in the past 15 years that among the processes of lightning is some mechanism capable of generating gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...

s, which escape the atmosphere and are observed by orbiting spacecraft. Brought to light by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's Gerald Fishman in 1994 in an article in Science, these so-called terrestrial gamma-ray flash
Terrestrial gamma-ray flash
Terrestrial gamma-ray flashes are bursts of gamma rays in the Earth's atmosphere. TGFs have been recorded to last 0.2 to 3.5 milliseconds, and have energies of up to 20 MeV. They are probably caused by electric fields produced above thunderstorms...

es (TGFs) were observed by accident, while he was documenting instances of extraterrestrial gamma ray bursts observed by the Compton Gamma Ray Observatory (CGRO). TGFs are much shorter in duration, however, lasting only about 1 ms.

Professor Umran Inan of Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...

 linked a TGF to an individual lightning stroke occurring within 1.5 ms of the TGF event, proving for the first time that the TGF was of atmospheric origin and associated with lightning strikes.

CGRO recorded only about 77 events in 10 years; however, more recently the Reuven Ramaty High Energy Solar Spectroscopic Imager
Reuven Ramaty High Energy Solar Spectroscopic Imager
Reuven Ramaty High Energy Solar Spectroscopic Imager is the sixth mission in the line of NASA Small Explorer missions...

 (RHESSI) spacecraft, as reported by David Smith of UC Santa Cruz
University of California, Santa Cruz
The University of California, Santa Cruz, also known as UC Santa Cruz or UCSC, is a public, collegiate university; one of ten campuses in the University of California...

, has been observing TGFs at a much higher rate, indicating that these occur about 50 times per day globally (still a very small fraction of the total lightning on the planet). The energy levels recorded exceed 20 MeV.

Scientists from Duke University
Duke University
Duke University is a private research university located in Durham, North Carolina, United States. Founded by Methodists and Quakers in the present day town of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco industrialist James B...

 have also been studying the link between certain lightning events and the mysterious gamma ray emissions that emanate from the Earth's own atmosphere, in light of newer observations of TGFs made by RHESSI. Their study suggests that this gamma radiation fountains upward from starting points at surprisingly low altitudes in thunderclouds.

Steven Cummer, from Duke University's Pratt School of Engineering
Edmund T. Pratt Jr. School of Engineering
The Edmund T. Pratt Jr. School of Engineering is one of two undergraduate schools at Duke University in Durham, North Carolina, USA. The other is the Trinity College of Arts and Sciences. It is also one of ten graduate and professional schools at Duke...

, said, "These are higher energy gamma rays than come from the sun. And yet here they are coming from the kind of terrestrial thunderstorm that we see here all the time."

Early hypotheses of this pointed to lightning generating high electric fields and driving relativistic runaway electron avalanche at altitudes well above the cloud where the thin atmosphere allows gamma rays to easily escape into space, similar to the way sprites
Upper-atmospheric lightning
Upper-atmospheric lightning or upper-atmospheric discharge are terms sometimes used by researchers to refer to a family of short-lived electrical-breakdown phenomena that occur well above the altitudes of normal lightning and storm clouds. Upper-atmospheric lightning is believed to be electrically...

 are generated. Subsequent evidence however, has suggested instead that TGFs may be produced by driving relativistic electron avalanches within or just above high thunderclouds. Though hindered by atmospheric absorption of the escaping gamma rays, these theories do not require the exceptionally intense lightning that high altitude theories of TGF generation rely on.

The role of TGFs and their relationship to lightning remains a subject of ongoing scientific study.

Sound

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
Kinetic theory
The kinetic theory of gases describes a gas as a large number of small particles , all of which are in constant, random motion. The rapidly moving particles constantly collide with each other and with the walls of the container...

 dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...

 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
Echo (phenomenon)
In audio signal processing and acoustics, an echo is a reflection of sound, arriving at the listener some time after the direct sound. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single...

 from terrain, and by the typically multiple-stroke characteristic of the lightning strike.

Since light travels
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...

 at a significantly greater speed than sound
Speed of sound
The speed of sound is the distance travelled during a unit of time by a sound wave propagating through an elastic medium. In dry air at , the speed of sound is . This is , or about one kilometer in three seconds or approximately one mile in five seconds....

 through air, an observer can approximate the distance to the strike by timing the interval between the visible lightning and the audible thunder it generates. At standard
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

 atmospheric temperature and pressures near ground level, sound will travel at roughly 343 m/s
Metre per second
Metre per second is an SI derived unit of both speed and velocity , defined by distance in metres divided by time in seconds....

 (1125 ft/sec
Feet per second
The foot per second is a unit of both speed and velocity . It expresses the distance in feet traveled or displaced, divided by the time in seconds...

); a lightning flash preceding its thunder by five seconds would be about one mile (1.6 km) distant. A flash preceding thunder by three seconds is about one kilometer distant. Consequently, a lightning strike observed at a very close distance (within 100 meters) will be accompanied by the sound of a loud snap, thunder almost instantaneously and the smell of ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...

 (O3).

Lightning-induced magnetism

The movement of electrical charges produces a magnetic field (see electromagnetism
Electromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...

). 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
Remanence
Remanence or remanent magnetization is the magnetization left behind in a ferromagnetic material after an external magnetic field is removed. It is also the measure of that magnetization. Colloquially, when a magnet is "magnetized" it has remanence...

 magnetism, or LIRM. These currents follow the least resistive path, often horizontally near the surface but sometimes vertically, where faults, ore bodies, or ground water offers a less resistive path. Lightning-induced magnetic anomalies can be mapped in the ground, and analysis of magnetized materials can confirm lightning was the source of the magnetization and provide an estimate of the peak current of the lightning discharge.

Records and locations




An old estimate of the frequency of lightning on Earth was 100 times a second. Now that there are satellites that can detect lightning, including in places where there is nobody to observe it, it is known to occur on average 44 ± 5 times a second, for a total of nearly 1.4 billion flashes per year; 75% of these flashes are either cloud-to-cloud or intra-cloud and 25% are cloud-to-ground.

The maps on the right show that lightning is not distributed evenly around the planet. Approximately 70% of lightning occurs in the tropics where the majority of thunderstorms occur. The place where lightning occurs most often (according to the data from 2004–2005) is near the small village of Kifuka in the mountains of eastern Democratic Republic of the Congo
Democratic Republic of the Congo
The Democratic Republic of the Congo is a state located in Central Africa. It is the second largest country in Africa by area and the eleventh largest in the world...

, where the elevation
Elevation
The elevation of a geographic location is its height above a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface ....

 is around 975 metres (3,198.8 ft). On average this region receives 158 lightning strikes per square kilometre (approx. 0.4 square mile) a year. Above the Catatumbo river, which feeds Lake Maracaibo
Lake Maracaibo
Lake Maracaibo is a large brackish bay in Venezuela at . It is connected to the Gulf of Venezuela by Tablazo Strait at the northern end, and fed by numerous rivers, the largest being the Catatumbo. It is commonly considered a lake rather than a bay or lagoon, and at 13,210 km² it would be the...

 in Venezuela, Catatumbo lightning
Catatumbo lightning
The Catatumbo Lightning is an atmospheric phenomenon in Venezuela. It occurs strictly in an area located over the mouth of the Catatumbo River where it empties into Lake Maracaibo...

 flashes several times per minute, 140 to 160 nights per year, accounting for 25% of the world's production of upper-atmospheric ozone. Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

 has one of the highest rates of lightning activity in the world. The city of Teresina
Teresina
Teresina is the capital and most populous municipality in the Brazilian state of Piauí. It is located in North-central Piauí 366 km from the coast.It is therefore, the only capital in the Northeast that is not located on the shores of the Atlantic Ocean. With 814 439 inhabitants, it is the 19th...

 in northern Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 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"). In the US, Central Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 sees more lightning than any other area. For example, in what is called "Lightning Alley", an area from Tampa
Tampa, Florida
Tampa is a city in the U.S. state of Florida. It serves as the county seat for Hillsborough County. Tampa is located on the west coast of Florida. The population of Tampa in 2010 was 335,709....

, to Orlando
Orlando, Florida
Orlando is a city in the central region of the U.S. state of Florida. It is the county seat of Orange County, and the center of the Greater Orlando metropolitan area. According to the 2010 US Census, the city had a population of 238,300, making Orlando the 79th largest city in the United States...

, there are as many as 50 strikes per square mile (about 20 per km²) per year. The Empire State Building
Empire State Building
The Empire State Building is a 102-story landmark skyscraper and American cultural icon in New York City at the intersection of Fifth Avenue and West 34th Street. It has a roof height of 1,250 feet , and with its antenna spire included, it stands a total of 1,454 ft high. Its name is derived...

 is struck by lightning on average 23 times each year, and was once struck 8 times in 24 minutes.
  • Roy Sullivan
    Roy Sullivan
    Roy Cleveland Sullivan was a U.S. park ranger in Shenandoah National Park in Virginia. Between 1942 and 1977, Sullivan was hit by lightning on seven different occasions and survived all of them. For this reason, he gained a nickname "Human Lightning Conductor" or "Human Lightning Rod"...

     held a Guinness World Record after surviving 7 different lightning strikes across 35 years.

  • In July 2007, lightning killed up to 30 people when it struck a remote mountain village Ushari Dara in northwestern Pakistan
    Pakistan
    Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...

    .

  • On 31 October 2005, sixty-eight dairy cows, all in full milk, died on a farm at Fernbrook on the Waterfall Way
    Waterfall Way
    The Waterfall Way is a road and State Highway 78 in New South Wales, Australia. It runs east-west from the Pacific Highway to the New England Highway at Armidale. The route passes through some of New South Wales' most scenic countryside and has become well known as New South Wales best and...

     near Dorrigo, New South Wales
    Dorrigo, New South Wales
    Dorrigo is a small town located on the Waterfall Way in northern New South Wales, Australia. It is approximately 580 kilometres north of the state capital, Sydney via the Pacific Highway, and 60 kilometres from the coastal city of Coffs Harbour. The town is situated on the Dorrigo Plateau near the...

     after being struck by lightning. Three others were paralysed for several hours but they later made a full recovery. The cows were sheltering under a tree when it was struck by lightning and the electricity spread onto the surrounding soil killing the animals.


Lightning rarely strikes the open ocean, although some sea regions are lightning "hot spots". Winter storms passing off the east coast of the United States often erupt with electrical activity when they cross the warm waters of the Gulf Stream
Gulf Stream
The Gulf Stream, together with its northern extension towards Europe, the North Atlantic Drift, is a powerful, warm, and swift Atlantic ocean current that originates at the tip of Florida, and follows the eastern coastlines of the United States and Newfoundland before crossing the Atlantic Ocean...

. The Gulf Stream endures about the same number of lightning strikes as the southern plains of the USA.

Lightning detection

The earliest detector invented to warn of the approach of a thunder storm was the lightning bell. Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

 installed one such device in his house. The detector was based on an electrostatic device called the 'electric chimes' invented by Andrew Gordon
Andrew Gordon (Benedictine)
Andrew Gordon was a Scottish Benedictine monk, physicist, and inventor. He made the first electric motor.-Life:...

 in 1742.

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

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.

Notable lightning strikes

Some lightning strike
Lightning strike
Lightning strikes are electrical discharges caused by lightning, typically during thunderstorms.Humans can be hit by lightning directly when outdoors. Contrary to popular notion, there is no 'safe' location outdoors. People have been struck in sheds and makeshift shelters...

s have caused either numerous fatalities or great damage. The following is a partial list:
  • In 1660, lightning struck the gunpowder magazine at Osaka Castle
    Osaka Castle
    is a Japanese castle in Chūō-ku, Osaka, Japan.Originally called Ozakajō, it is one of Japan's most famous castles, and played a major role in the unification of Japan during the sixteenth century of the Azuchi-Momoyama period.-Description:...

    , Japan
    Japan
    Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

    ; the resultant explosion set the castle on fire. In 1665, lightning struck the main tower of the castle and it burned down to the foundation.
  • A particularly deadly lightning incident occurred in Brescia
    Brescia
    Brescia is a city and comune in the region of Lombardy in northern Italy. It is situated at the foot of the Alps, between the Mella and the Naviglio, with a population of around 197,000. It is the second largest city in Lombardy, after the capital, Milan...

    , Italy
    Italy
    Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

     in 1769. Lightning struck the Church of St. Nazaire, igniting the 100 tons of gunpowder in its vaults; the resulting explosion killed 3000 people and destroyed a sixth of the city.
  • 1902: A lightning strike damaged the upper section of the Eiffel Tower
    Eiffel Tower
    The Eiffel Tower is a puddle iron lattice tower located on the Champ de Mars in Paris. Built in 1889, it has become both a global icon of France and one of the most recognizable structures in the world...

    , requiring the reconstruction of its top
  • December 8, 1963: Pan Am Flight 214
    Pan Am Flight 214
    Pan Am Flight 214, a Boeing 707-121 registered as , was en route from Baltimore to Philadelphia on December 8, 1963, when it crashed near Elkton, Maryland after being hit by lightning, killing all 81 on board.-Flight history:...

     crashed as result of a lightning strike, killing all 81 people on board.
  • July 12, 1970, the central mast of the Orlunda radio transmitter collapsed after a lightning strike destroyed its basement insulator.
  • December 24, 1971: LANSA Flight 508
    LANSA Flight 508
    LANSA Flight 508 was a Lockheed L-188A Electra turboprop, registered OB-R-941, operated as a scheduled domestic passenger flight by Lineas Aéreas Nacionales Sociedad Anonima , that crashed in a thunderstorm en route from Lima, Peru to Pucallpa, Peru, on December 24, 1971, killing 91 people –...

     crashed as a result of lightning in Peru
    Peru
    Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

    , with 91 people killed.
  • November 2, 1994, lightning struck fuel tanks in Dronka, Egypt
    Egypt
    Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

     and caused 469 fatalities.

Harvesting lightning energy

Since the late 1980s there have been several attempts to investigate the possibility of harvesting energy from lightning. While a single bolt of lightning carries a relatively large amount of energy (approximately 5 billion joules), this energy is concentrated in a small location and is passed during an extremely short period of time (millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....

s); therefore, extremely high electrical power is involved. It has been proposed that the energy contained in lightning be used to generate hydrogen
Hydrogen economy
The hydrogen economy is a proposed system of delivering energy using hydrogen. The term hydrogen economy was coined by John Bockris during a talk he gave in 1970 at General Motors Technical Center....

 from water, or to harness the energy from rapid heating of water due to lightning.

A technology capable of harvesting lightning energy would need to be able to rapidly capture the high power involved in a lightning bolt. Several schemes have been proposed, but the ever-changing energy involved in each lightning bolt render lightning power harvesting from ground based rods impractical - too high, it will damage the storage, too low and it may not work. According to Northeastern University physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

s Stephen Reucroft and John Swain, a lightning bolt carries a few million joules of energy, enough to power a 100-watt bulb for 5.5 hours. Additionally, lightning is sporadic, and therefore energy would have to be collected and stored; it is difficult to convert high-voltage electrical power to the lower-voltage power that can be stored.

In the summer of 2007, an alternative energy
Alternative energy
Alternative energy is an umbrella term that refers to any source of usable energy intended to replace fuel sources without the undesired consequences of the replaced fuels....

 company called Alternate Energy Holdings, Inc. (AEHI) tested a method for capturing the energy in lightning bolts. The design for the system had been purchased from an Illinois
Illinois
Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

 inventor named Steve LeRoy, who had reportedly been able to power a 60-watt light bulb for 20 minutes using the energy captured from a small flash of artificial lightning. The method involved a tower, a means of shunting off a large portion of the incoming energy, and a capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...

 to store the rest. According to Donald Gillispie, CEO of AEHI, they "couldn't make it work," although "given enough time and money, you could probably scale this thing up... it's not black magic; it's truly math and science, and it could happen."

According to Dr. Martin A. Uman
Martin A. Uman
Martin Allan Uman is an American engineer. He has been acknowledged by the American Geophysical Union as one of the world's leading authorities on lightning....

, co-director of the Lightning Research Laboratory at the University of Florida
University of Florida
The University of Florida is an American public land-grant, sea-grant, and space-grant research university located on a campus in Gainesville, Florida. The university traces its historical origins to 1853, and has operated continuously on its present Gainesville campus since September 1906...

 and a leading authority on lightning, a single lightning strike, while fast and bright, contains very little energy, and dozens of lighting towers like those used in the system tested by AEHI would be needed to operate five 100-watt light bulbs for the course of a year. When interviewed by The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

, he stated that the energy in a thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

 is comparable to that of an atomic bomb, but trying to harvest the energy of lightning from the ground is "hopeless".

Another major challenge when attempting to harvest energy from lighting is the impossibility of predicting when and where thunderstorms will occur. Even during a storm, it is very difficult to tell where exactly lightning will strike.

A relatively easy method is the direct harvesting of atmospheric charge before it turns into lightning. At a small scale, it was done a few times with the most known example being Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

's experiment with his kite. However, to collect reasonable amounts of energy very large constructions are required, and it is relatively hard to utilize the resulting extremely high voltage with reasonable efficiency.

As expressions and symbols

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
Probability
Probability is ordinarily used to describe an attitude of mind towards some proposition of whose truth we arenot certain. The proposition of interest is usually of the form "Will a specific event occur?" The attitude of mind is of the form "How certain are we that the event will occur?" The...

 of strikes at any given location, repeat lightning strikes have a very low probability (but are not impossible). Similarly, "A bolt from the blue" refers to something totally unexpected.

Some political parties use lightning flashes as a symbol of power, such as the People's Action Party
People's Action Party
The People's Action Party is the leading political party in Singapore. It has been the city-state's ruling political party since 1959....

 in Singapore
Singapore
Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...

 and the British Union of Fascists
British Union of Fascists
The British Union was a political party in the United Kingdom formed in 1932 by Sir Oswald Mosley as the British Union of Fascists, in 1936 it changed its name to the British Union of Fascists and National Socialists and then in 1937 to simply the British Union...

 during the 1930s. The Schutzstaffel
Schutzstaffel
The Schutzstaffel |Sig runes]]) was a major paramilitary organization under Adolf Hitler and the Nazi Party. Built upon the Nazi ideology, the SS under Heinrich Himmler's command was responsible for many of the crimes against humanity during World War II...

, the secret police
Secret police
Secret police are a police agency which operates in secrecy and beyond the law to protect the political power of an individual dictator or an authoritarian political regime....

 of the Nazi Party, used the Sig rune in their logo which symbolizes lightning. The German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

 word Blitzkrieg
Blitzkrieg
For other uses of the word, see: Blitzkrieg Blitzkrieg is an anglicized word describing all-motorised force concentration of tanks, infantry, artillery, combat engineers and air power, concentrating overwhelming force at high speed to break through enemy lines, and, once the lines are broken,...

, which means "lightning war", was a major offensive strategy of the German army during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

.

In French
French language
French is a Romance language spoken as a first language in France, the Romandy region in Switzerland, Wallonia and Brussels in Belgium, Monaco, the regions of Quebec and Acadia in Canada, and by various communities elsewhere. Second-language speakers of French are distributed throughout many parts...

 and Italian
Italian language
Italian is a Romance language spoken mainly in Europe: Italy, Switzerland, San Marino, Vatican City, by minorities in Malta, Monaco, Croatia, Slovenia, France, Libya, Eritrea, and Somalia, and by immigrant communities in the Americas and Australia...

, 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
Cognate
In linguistics, cognates are words that have a common etymological origin. This learned term derives from the Latin cognatus . Cognates within the same language are called doublets. Strictly speaking, loanwords from another language are usually not meant by the term, e.g...

 of the English word "rays". The name of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's most celebrated thoroughbred
Thoroughbred
The Thoroughbred is a horse breed best known for its use in horse racing. Although the word thoroughbred is sometimes used to refer to any breed of purebred horse, it technically refers only to the Thoroughbred breed...

 horse, Phar Lap
Phar Lap
Phar Lap was a champion Thoroughbred racehorse whose achievements captured the public's imagination during the early years of the Great Depression. Foaled in New Zealand, he was trained and raced in Australia. Phar Lap dominated Australian racing during a distinguished career, winning a Melbourne...

, derives from the shared Zhuang
Standard Zhuang
The standard Zhuang language is the variety of Zhuang spoken in Wuming County in the Guangxi Zhuang Autonomous Region of the People's Republic of China, where it is an official language.-Classification:...

 and Thai
Thai language
Thai , also known as Central Thai and Siamese, is the national and official language of Thailand and the native language of the Thai people, Thailand's dominant ethnic group. Thai is a member of the Tai group of the Tai–Kadai language family. Historical linguists have been unable to definitively...

 word for lightning.

The bolt of lightning in heraldry
Heraldry
Heraldry is the profession, study, or art of creating, granting, and blazoning arms and ruling on questions of rank or protocol, as exercised by an officer of arms. Heraldry comes from Anglo-Norman herald, from the Germanic compound harja-waldaz, "army commander"...

 is called a thunderbolt
Thunderbolt
A thunderbolt is a discharge of lightning accompanied by a loud thunderclap or its symbolic representation. In its original usage the word may also have been a description of meteors, or, as Plato suggested in Timaeus, of the consequences of a close approach between two planetary cosmic bodies,...

 and is shown as a zigzag with non-pointed ends. This symbol usually represents power and speed. In Hindu mythology
Hindu mythology
Hindu religious literature is the large body of traditional narratives related to Hinduism, notably as contained in Sanskrit literature, such as the Sanskrit epics and the Puranas. As such, it is a subset of Nepali and Indian culture...

 the thunderbolt (Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 Vajra
Vajra
Vajra is a Sanskrit word meaning both thunderbolt and diamond...

) is an attribute of the Hindu god
Deva (Hinduism)
' is the Sanskrit word for god or deity, its related feminine term is devi. In modern Hinduism, it can be loosely interpreted as any benevolent supernatural beings. The devs in Hinduism, also called Suras, are often juxtaposed to the Asuras, their half brothers. Devs are also the maintainers of...

 Indra
Indra
' or is the King of the demi-gods or Devas and Lord of Heaven or Svargaloka in Hindu mythology. He is also the God of War, Storms, and Rainfall.Indra is one of the chief deities in the Rigveda...

. The lightning bolt or thunderbolt appears also as a heraldic charge
Charge (heraldry)
In heraldry, a charge is any emblem or device occupying the field of an escutcheon . This may be a geometric design or a symbolic representation of a person, animal, plant, object or other device...

.

The lightning bolt is used to represent the instantaneous communication capabilities of electrically-powered telegraphs and radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...

s, and is a common insignia for military communications
Military communications
Historically, the first military communications had the form of sending/receiving simple signals . Respectively, the first distinctive tactics of military communications were called Signals, while units specializing in those tactics received the Signal Corps name...

 units throughout the world. A lightning bolt is also the NATO symbol for a signal asset.

Ceraunoscopy

This is divination
Divination
Divination is the attempt to gain insight into a question or situation by way of an occultic standardized process or ritual...

 by observing lightning or by listening to thunder. It is a type of aeromancy
Aeromancy
Aeromancy is divination conducted by interpreting atmospheric conditions. Alternate spellings include Arologie, Aeriology and Aërology.-Practice:...

. People have also sought to control lightning by conducting rituals or casting spells.

Religion

Over the centuries, lightning in cultures was viewed as part of a deity or a deity in of itself. One of the most classic portrayals of this is of the Greek god Zeus
Zeus
In the ancient Greek religion, Zeus was the "Father of Gods and men" who ruled the Olympians of Mount Olympus as a father ruled the family. He was the god of sky and thunder in Greek mythology. His Roman counterpart is Jupiter and his Etruscan counterpart is Tinia.Zeus was the child of Cronus...

. An ancient story is when Zeus
Zeus
In the ancient Greek religion, Zeus was the "Father of Gods and men" who ruled the Olympians of Mount Olympus as a father ruled the family. He was the god of sky and thunder in Greek mythology. His Roman counterpart is Jupiter and his Etruscan counterpart is Tinia.Zeus was the child of Cronus...

 was at war against Kronus and the Titans
Titan (mythology)
In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age....

, he released his brothers, Hades
Hades
Hades , Hadēs, originally , Haidēs or , Aidēs , meaning "the unseen") was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...

 and Poseidon
Poseidon
Poseidon was the god of the sea, and, as "Earth-Shaker," of the earthquakes in Greek mythology. The name of the sea-god Nethuns in Etruscan was adopted in Latin for Neptune in Roman mythology: both were sea gods analogous to Poseidon...

, along with the Cyclopes
Cyclops
A cyclops , in Greek mythology and later Roman mythology, was a member of a primordial race of giants, each with a single eye in the middle of his forehead...

. In turn, the Cyclopes gave Zeus the thunderbolt as a weapon, which was near the beginning of Zeus himself. The thunderbolt became a popular symbol of Zeus and continues to be today.


The Aztecs portrayed lightning as a supernatural power of the god Tlaloc
Tlaloc
Tlaloc was an important deity in Aztec religion, a god of rain, fertility, and water. He was a beneficent god who gave life and sustenance, but he was also feared for his ability to send hail, thunder and lightning, and for being the lord of the powerful element of water. In Aztec iconography he...

, visualized as his axe. In mythology, Tlaloc was the bringer not only of beneficial rain but of storms, killer lightning bolts, flood, and disease.

The Classic Mayas personified lightning as a rain deity classified by scholars as God K
God K
God K is the Schellhas-Zimmermann-Taube designation of a codical Maya deity representing lightning . In earlier, especially Classic depictions, his main characteristics are a blade or torch running through his forehead, and a serpent for one of his legs...

. This deity has a leg shaped like a lightning serpent, and a forehead perforated by a lightning celt. A miniature God K is often wielded as an axe by the king.

In Slavic mythology
Slavic mythology
Slavic mythology is the mythological aspect of the polytheistic religion that was practised by the Slavs before Christianisation.The religion possesses many common traits with other religions descended from the Proto-Indo-European religion....

 the highest god of the pantheon is Perun
Perun
In Slavic mythology, Perun is the highest god of the pantheon and the god of thunder and lightning. His other attributes were the fire, mountains, the oak, iris, eagle, firmament , horses and carts, weapons and war...

, the god of thunder and lightning.

Pērkons/Perkūnas
Perkunas
Perkūnas was the common Baltic god of thunder, one of the most important deities in the Baltic pantheon. In both Lithuanian and Latvian mythology, he is documented as the god of thunder, rain, mountains, oak trees and the sky.-Etymology:...

 is the common Baltic
Baltic languages
The Baltic languages are a group of related languages belonging to the Balto-Slavic branch of the Indo-European language family and spoken mainly in areas extending east and southeast of the Baltic Sea in Northern Europe...

 god of thunder, one of the most important deities in the Baltic pantheon. In both Latvian and Lithuanian mythology, he is documented as the god of thunder, rain, mountains, oak trees and the sky.

In Norse mythology
Norse mythology
Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

, Thor
Thor
In Norse mythology, Thor is a hammer-wielding god associated with thunder, lightning, storms, oak trees, strength, the protection of mankind, and also hallowing, healing, and fertility...

 is the god of thunder and the sound of thunder comes from the chariot he rides across the sky. The lightning comes from his hammer Mjölnir.

In Finnish mythology
Finnish mythology
Finnish mythology is the mythology that went with Finnish paganism which was practised by the Finnish people prior to Christianisation. It has many features shared with fellow Finnic Estonian mythology and its non-Finnic neighbours, the Balts and the Scandinavians...

, Ukko
Ukko
In Finnish mythology, Ukko, in Estonian mythology Uku, is a god of sky, weather, crops and other natural things. He is the most significant god in Finnish and Estonian mythologies, and created the goddess Ilmatar, creator of the world. The Finnish word ukkonen, thunderstorm, is derived from his...

 (engl. Old Man) is the god of thunder, sky and weather. The Finnish word for thunder is ukkonen, derived from the god's name.

In the Jewish religion, a blessing "...He who does acts of creation" is to be recited, upon sighting lightning. The Talmud
Talmud
The Talmud is a central text of mainstream Judaism. It takes the form of a record of rabbinic discussions pertaining to Jewish law, ethics, philosophy, customs and history....

 refers to the Hebrew word for the sky, ("Shamaim") - as built from fire and water ("Esh Umaim"), since the sky is the source of the inexplicable mixture of "fire" and water that come together, during rainstorms. This is mentioned in various prayers and discussed in writings of Kabbalah
Kabbalah
Kabbalah/Kabala is a discipline and school of thought concerned with the esoteric aspect of Rabbinic Judaism. It was systematized in 11th-13th century Hachmei Provence and Spain, and again after the Expulsion from Spain, in 16th century Ottoman Palestine...

.

In Islam
Islam
Islam . The most common are and .   : Arabic pronunciation varies regionally. The first vowel ranges from ~~. The second vowel ranges from ~~~...

, the Quran states: "He it is Who showeth you the lightning, a fear and a hope, and raiseth the heavy clouds. The thunder hymneth His praise and (so do) the angels for awe of Him. He launcheth the thunder-bolts and smiteth with them whom He will." (Qur'an 13:12–13) and, "Have you not seen how God makes the clouds move gently, then joins them together, then makes them into a stack, and then you see the rain come out of it..." (Quran, 24:43). The preceding verse, after mentioning clouds and rain, speaks about hail and lightning, "...And He sends down hail from mountains (clouds) in the sky, and He strikes with it whomever He wills, and turns it from whomever He wills."

In India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

, the Hindu
Hindu
Hindu refers to an identity associated with the philosophical, religious and cultural systems that are indigenous to the Indian subcontinent. As used in the Constitution of India, the word "Hindu" is also attributed to all persons professing any Indian religion...

 god Indra
Indra
' or is the King of the demi-gods or Devas and Lord of Heaven or Svargaloka in Hindu mythology. He is also the God of War, Storms, and Rainfall.Indra is one of the chief deities in the Rigveda...

 is considered the god of rains and lightning and the king of the Deva
Deva (Hinduism)
' is the Sanskrit word for god or deity, its related feminine term is devi. In modern Hinduism, it can be loosely interpreted as any benevolent supernatural beings. The devs in Hinduism, also called Suras, are often juxtaposed to the Asuras, their half brothers. Devs are also the maintainers of...

s.

In Japan, the Shinto
Shinto
or Shintoism, also kami-no-michi, is the indigenous spirituality of Japan and the Japanese people. It is a set of practices, to be carried out diligently, to establish a connection between present day Japan and its ancient past. Shinto practices were first recorded and codified in the written...

 god Raijin
Raijin
is a god of lightning, thunder and storms in the Shinto religion and in Japanese mythology.His name is derived from the Japanese words rai and shin . He is typically depicted as a demon beating drums to create thunder, usually with the symbol tomoe drawn on the drums...

 is considered the god of lightning and thunder. He is depicted as a demon who strikes a drum to create lightning.

In the traditional religion of the African Bantu
Bantu
Bantu is used as a general label for 300-600 ethnic groups in Africa of speakers of Bantu languages, distributed from Cameroon east across Central Africa and Eastern Africa to Southern Africa...

 tribes, such as the Baganda
Baganda
The Ganda are an ethnic group native to Buganda, a subnational kingdom within Uganda. Traditionally comprising 52 tribes the Ganda have a rich history and culture...

 and Banyoro of Uganda
Uganda
Uganda , officially the Republic of Uganda, is a landlocked country in East Africa. Uganda is also known as the "Pearl of Africa". It is bordered on the east by Kenya, on the north by South Sudan, on the west by the Democratic Republic of the Congo, on the southwest by Rwanda, and on the south by...

, lightning is a sign of the ire of the gods. The Baganda specifically attribute the lightning phenomenon to the god Kiwanuka
Kiwanuka
Kiwanuka may refer to:* Benedicto Kiwanuka , first Prime Minister of Uganda* Mathias Kiwanuka , player in the NFL, grandson of Benedicto Kiwanuka* Michael Kiwanuka, British soul musician...

, one of the main trio in the Lubaale gods of the sea or lake. Kiwanuka starts wild fires, strikes trees and other high buildings, and a number of shrines are established in the hills, mountains and plains to stay in his favor. Lightning is also known to be invoked upon one's enemies by uttering certain chants, prayers, and making sacrifices.

External links


Jets, sprites & elves

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