108-407: Lightning is a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground , temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy , depending on the type. This discharge may produce
216-508: A thundercloud moves over the surface of the Earth, an equal electric charge , but of opposite polarity, is induced on the Earth's surface underneath the cloud. The induced positive surface charge, when measured against a fixed point, will be small as the thundercloud approaches, increasing as the center of the storm arrives and dropping as the thundercloud passes. The referential value of the induced surface charge could be roughly represented as
324-797: A 126-ton schooner , the Lalla Rookh and used it as a base for entertaining friends and scientific colleagues. His maritime interests continued in 1871 when he was appointed to the Board of Enquiry into the sinking of HMS Captain . In June 1873, Thomson and Jenkin were on board the Hooper , bound for Lisbon with 2,500 miles (4,020 km) of cable when the cable developed a fault. An unscheduled 16-day stop-over in Madeira followed, and Thomson became good friends with Charles R. Blandy and his three daughters. On 2 May 1874 he set sail for Madeira on
432-461: A base and carbon dioxide is an acidic gas, it is possible that charged water clouds in which the negative charge is in the form of the aqueous hydroxide ion, interact with atmospheric carbon dioxide to form aqueous carbonate ions and aqueous hydrogen carbonate ions. The typical cloud-to-ground lightning flash culminates in the formation of an electrically conducting plasma channel through the air in excess of 5 km (3.1 mi) tall, from within
540-523: A bell curve. The oppositely charged regions create an electric field within the air between them. This electric field varies in relation to the strength of the surface charge on the base of the thundercloud – the greater the accumulated charge, the higher the electrical field. The best-studied and understood form of lightning is cloud to ground (CG) lightning. Although more common, intra-cloud (IC) and cloud-to-cloud (CC) flashes are very difficult to study given there are no "physical" points to monitor inside
648-459: A bidirectional leader initiates between the main negative and lower positive charge regions in a thundercloud. The weaker positive charge region is filled quickly by the negative leader which then propagates toward the inductively-charged ground. The positively and negatively charged leaders proceed in opposite directions, positive upwards within the cloud and negative towards the earth. Both ionic channels proceed, in their respective directions, in
756-544: A brilliant, blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder . High-speed videos (examined frame-by-frame) show that most negative CG lightning flashes are made up of 3 or 4 individual strokes, though there may be as many as 30. Each re-strike
864-420: A charge opposite of that of the leader tip. The negative end of the bidirectional leader fills a positive charge region, also called a well, inside the cloud while the positive end fills a negative charge well. Leaders often split, forming branches in a tree-like pattern. In addition, negative and some positive leaders travel in a discontinuous fashion, in a process called "stepping". The resulting jerky movement of
972-409: A conductive portion of the main leader network, a return stroke-like process occurs and a dart leader travels across all or a portion of the length of the original leader. The dart leaders making connections with the ground are what cause a majority of subsequent return strokes. Each successive stroke is preceded by intermediate dart leader strokes that have a faster rise time but lower amplitude than
1080-426: A copy of his paper, but when Joule eventually read it he wrote to Thomson on 6 October, claiming that his studies had demonstrated conversion of heat into work but that he was planning further experiments. Thomson replied on 27 October, revealing that he was planning his own experiments and hoping for a reconciliation of their two sides. Thomson returned to critique Carnot's original publication and read his analysis to
1188-481: A form of the second law: It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects. In the paper, Thomson supports the theory that heat was a form of motion but admits that he had been influenced only by the thought of Sir Humphry Davy and the experiments of Joule and Julius Robert von Mayer , maintaining that experimental demonstration of
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#17327719604971296-482: A great distance but not heard; dry lightning , which can cause forest fires ; and ball lightning , which is rarely observed scientifically. Humans have deified lightning for millennia. Idiomatic expressions derived from lightning, such as the English expression "bolt from the blue", are common across languages. At all times people have been fascinated by the sight and difference of lightning. The fear of lightning
1404-445: A high-resistance medium must obstruct the free, unimpeded equalization of the opposite charges. The atmosphere provides the electrical insulation, or barrier, that prevents free equalization between charged regions of opposite polarity. It is well understood that during a thunderstorm there is charge separation and aggregation in certain regions of the cloud; however, the exact processes by which this occurs are not fully understood. As
1512-412: A negative charge. Updrafts within a storm cloud separate the lighter ice crystals from the heavier graupel, causing the top region of the cloud to accumulate a positive space charge while the lower level accumulates a negative space charge. Because the concentrated charge within the cloud must exceed the insulating properties of air, and this increases proportionally to the distance between the cloud and
1620-600: A number of much shorter flashes (strokes) of around 60 to 70 microseconds . Many factors affect the frequency, distribution, strength and physical properties of a typical lightning flash in a particular region of the world. These factors include ground elevation, latitude , prevailing wind currents, relative humidity , and proximity to warm and cold bodies of water. To a certain degree, the proportions of intra-cloud, cloud-to-cloud, and cloud-to-ground lightning may also vary by season in middle latitudes . Because human beings are terrestrial and most of their possessions are on
1728-465: A number of successive spurts. Each leader "pools" ions at the leading tips, shooting out one or more new leaders, momentarily pooling again to concentrate charged ions, then shooting out another leader. The negative leader continues to propagate and split as it heads downward, often speeding up as it gets closer to the Earth's surface. About 90% of ionic channel lengths between "pools" are approximately 45 m (148 ft) in length. The establishment of
1836-514: A scale would be "quite independent of the physical properties of any specific substance." By employing such a "waterfall", Thomson postulated that a point would be reached at which no further heat (caloric) could be transferred, the point of absolute zero about which Guillaume Amontons had speculated in 1702. "Reflections on the Motive Power of Heat", published by Carnot in French in 1824,
1944-491: A series of countless events as a feature created by nature. The act of: Violent meteorological phenomena are called storms . Regular, cyclical phenomena include seasons and atmospheric circulation . climate change is often semi-regular. Atmospheric optical phenomena include: William Thomson, 1st Baron Kelvin William Thomson, 1st Baron Kelvin (26 June 1824 – 17 December 1907 )
2052-426: A third, more substantial P.Q.R. paper On the uniform motion of heat in homogeneous solid bodies, and its connection with the mathematical theory of electricity . In the paper he made remarkable connections between the mathematical theories of thermal conduction and electrostatics , an analogy that James Clerk Maxwell was ultimately to describe as one of the most valuable science-forming ideas . William's father
2160-451: A threshold and form upward streamers. Once a downward leader connects to an available upward leader, a process referred to as attachment, a low-resistance path is formed and discharge may occur. Photographs have been taken in which unattached streamers are clearly visible. The unattached downward leaders are also visible in branched lightning, none of which are connected to the earth, although it may appear they are. High-speed videos can show
2268-472: A whole the reverse of concentration is gradually going on – I believe that no physical action can ever restore the heat emitted from the Sun, and that this source is not inexhaustible; also that the motions of the Earth and other planets are losing vis viva which is converted into heat; and that although some vis viva may be restored for instance to the earth by heat received from the sun, or by other means, that
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#17327719604972376-519: A wide range of electromagnetic radiation , from heat created by the rapid movement of electrons , to brilliant flashes of visible light in the form of black-body radiation . Lightning causes thunder , a sound from the shock wave which develops as gases in the vicinity of the discharge experience a sudden increase in pressure. Lightning occurs commonly during thunderstorms as well as other types of energetic weather systems, but volcanic lightning can also occur during volcanic eruptions . Lightning
2484-485: Is an atmospheric electrical phenomenon and contributes to the global atmospheric electrical circuit . The three main kinds of lightning are distinguished by where they occur: either inside a single thundercloud (intra-cloud), between two clouds (cloud-to-cloud), or between a cloud and the ground (cloud-to-ground), in which case it is referred to as a lightning strike . Many other observational variants are recognized, including " heat lightning ", which can be seen from
2592-563: Is called astraphobia . The first known photograph of lightning is from 1847, by Thomas Martin Easterly . The first surviving photograph is from 1882, by William Nicholson Jennings , a photographer who spent half his life capturing pictures of lightning and proving its diversity. There is growing evidence that lightning activity is increased by particulate emissions (a form of air pollution). However, lightning may also improve air quality and clean greenhouse gases such as methane from
2700-415: Is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science , whatever the matter may be. Though eminent in the academic field, Thomson was obscure to the general public. In September 1852, he married childhood sweetheart Margaret Crum, daughter of Walter Crum ; but her health broke down on their honeymoon, and over
2808-417: Is separated by a relatively large amount of time, typically 40 to 50 milliseconds, as other charged regions in the cloud are discharged in subsequent strokes. Re-strikes often cause a noticeable " strobe light " effect. To understand why multiple return strokes utilize the same lightning channel, one needs to understand the behavior of positive leaders, which a typical ground flash effectively becomes following
2916-474: Is strongest on grounded objects whose tops are closest to the base of the thundercloud, such as trees and tall buildings. If the electric field is strong enough, a positively charged ionic channel, called a positive or upward streamer , can develop from these points. This was first theorized by Heinz Kasemir. As negatively charged leaders approach, increasing the localized electric field strength, grounded objects already experiencing corona discharge will exceed
3024-460: Is usually negatively charged, this is where most CG lightning originates. This region is typically at the elevation where freezing occurs within the cloud. Freezing, combined with collisions between ice and water, appears to be a critical part of the initial charge development and separation process. During wind-driven collisions, ice crystals tend to develop a positive charge, while a heavier, slushy mixture of ice and water (called graupel ) develops
3132-535: The Great Eastern . Thomson introduced a new method of deep-sea depth sounding , in which a steel piano wire replaces the ordinary hand line. The wire glides so easily to the bottom that "flying soundings" can be taken while the ship is at full speed. Thomson added a pressure gauge to register the depth of the sinker. About the same time he revived the Sumner method of finding a ship's position, and calculated
3240-624: The British Association for the Advancement of Science annual meeting in Oxford . At that meeting, he heard James Prescott Joule making yet another of his, so far, ineffective attempts to discredit the caloric theory of heat and the theory of the heat engine built upon it by Sadi Carnot and Émile Clapeyron . Joule argued for the mutual convertibility of heat and mechanical work and for their mechanical equivalence. Thomson
3348-617: The County of Ayr . The title refers to the River Kelvin , which flows near his laboratory at the University of Glasgow's Gilmorehill home at Hillhead . Despite offers of elevated posts from several world-renowned universities, Kelvin refused to leave Glasgow, remaining until his retirement from that post in 1899. Active in industrial research and development, he was recruited around 1899 by George Eastman to serve as vice-chairman of
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3456-455: The Kelvin water dropper . The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. The electrical charging of solid water ice has also been considered. The charged species were again considered to be the hydrogen ion and the hydroxide ion. An electron is not stable in liquid water concerning a hydroxide ion plus dissolved hydrogen for
3564-524: The Lalla Rookh . As he approached the harbour, he signalled to the Blandy residence "Will you marry me?" and Fanny (Blandy's daughter Frances Anna Blandy) signalled back "Yes". Thomson married Fanny, 13 years his junior, on 24 June 1874. Over the period 1855 to 1867, Thomson collaborated with Peter Guthrie Tait on a textbook that founded the study of mechanics first on the mathematics of kinematics ,
3672-689: The Royal Society of Edinburgh in January 1849, still convinced that the theory was fundamentally sound. However, though Thomson conducted no new experiments, over the next two years he became increasingly dissatisfied with Carnot's theory and convinced of Joule's. In February 1851 he sat down to articulate his new thinking. He was uncertain of how to frame his theory, and the paper went through several drafts before he settled on an attempt to reconcile Carnot and Joule. During his rewriting, he seems to have considered ideas that would subsequently give rise to
3780-521: The University of Glasgow , not out of any precociousness; the university provided many of the facilities of an elementary school for able pupils, and this was a typical starting age. In school, he showed a keen interest in the classics along with his natural interest in the sciences. At age 12 he won a prize for translating Lucian of Samosata's Dialogues of the Gods from Ancient Greek to English. In
3888-584: The elevation is around 975 m (3,200 ft). On average, this region receives 158 lightning strikes per square kilometre per year (410/sq mi/yr). Other lightning hotspots include Singapore and Lightning Alley in Central Florida . According to the World Meteorological Organization , on April 29, 2020, a bolt 768 km (477.2 mi) long was observed in the southern U.S.—sixty km (37 mi) longer than
3996-458: The heat death paradox (Kelvin's paradox) in 1862, which uses the second law of thermodynamics to disprove the possibility of an infinitely old universe; this paradox was later extended by William Rankine . In final publication, Thomson retreated from a radical departure and declared "the whole theory of the motive power of heat is founded on ... two ... propositions, due respectively to Joule, and to Carnot and Clausius." Thomson went on to state
4104-425: The second law of thermodynamics . In Carnot's theory, lost heat was absolutely lost, but Thomson contended that it was " lost to man irrecoverably; but not lost in the material world". Moreover, his theological beliefs led Thomson to extrapolate the second law to the cosmos, originating the idea of universal heat death . I believe the tendency in the material world is for motion to become diffused, and that as
4212-402: The transatlantic telegraph project , he was knighted in 1866 by Queen Victoria , becoming Sir William Thomson. He had extensive maritime interests and worked on the mariner's compass , which previously had limited reliability. Kelvin was ennobled in 1892 in recognition of his achievements in thermodynamics, and of his opposition to Irish Home Rule , becoming Baron Kelvin, of Largs in
4320-475: The triboelectric effect leading to electron or ion transfer between colliding bodies. Uncharged, colliding water-drops can become charged because of charge transfer between them (as aqueous ions) in an electric field as would exist in a thunder cloud. The main charging area in a thunderstorm occurs in the central part of the storm where air is moving upward rapidly (updraft) and temperatures range from −15 to −25 °C (5 to −13 °F); see Figure 1. In that area,
4428-583: The tropics where atmospheric convection is the greatest. This occurs from both the mixture of warmer and colder air masses , as well as differences in moisture concentrations, and it generally happens at the boundaries between them . The flow of warm ocean currents past drier land masses, such as the Gulf Stream , partially explains the elevated frequency of lightning in the Southeast United States . Because large bodies of water lack
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4536-611: The "continental" mathematics resisted by a British establishment still working in the shadow of Sir Isaac Newton . Unsurprisingly, Fourier's work had been attacked by domestic mathematicians, Philip Kelland authoring a critical book. The book motivated Thomson to write his first published scientific paper under the pseudonym P.Q.R. , defending Fourier, which was submitted to The Cambridge Mathematical Journal by his father. A second P.Q.R. paper followed almost immediately. While on holiday with his family in Lamlash in 1841, he wrote
4644-415: The 1840s as has the electrification of pure liquid water by the triboelectric effect. William Thomson (Lord Kelvin) demonstrated that charge separation in water occurs in the usual electric fields at the Earth's surface and developed a continuous electric field measuring device using that knowledge. The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with
4752-470: The Carnot–Clapeyron theory further through his dissatisfaction that the gas thermometer provided only an operational definition of temperature. He proposed an absolute temperature scale in which "a unit of heat descending from a body A at the temperature T ° of this scale, to a body B at the temperature ( T −1)°, would give out the same mechanical effect [work] , whatever be the number T ." Such
4860-424: The Earth where lightning can damage or destroy them, cloud-to-ground (CG) lightning is the most studied and best understood of the three types, even though in-cloud (IC) and cloud-to-cloud (CC) are more common types of lightning. Lightning's relative unpredictability limits a complete explanation of how or why it occurs, even after hundreds of years of scientific investigation. About 70% of lightning occurs over land in
4968-750: The Kelvin–Joule effect, and the published results did much to bring about general acceptance of Joule's work and the kinetic theory . Thomson published more than 650 scientific papers and applied for 70 patents (not all were issued). Regarding science, Thomson wrote the following: In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge
5076-427: The academic year 1839/1840, Thomson won the class prize in astronomy for his "Essay on the figure of the Earth" which showed an early facility for mathematical analysis and creativity. His physics tutor at this time was his namesake, David Thomson . Throughout his life, he would work on the problems raised in the essay as a coping strategy during times of personal stress. On the title page of this essay Thomson wrote
5184-547: The access he was given unsatisfactory, and the Agamemnon had to return home following a disastrous storm in June 1858. In London, the board was about to abandon the project and mitigate their losses by selling the cable. Thomson, Cyrus West Field and Curtis M. Lampson argued for another attempt and prevailed, Thomson insisting that the technical problems were tractable. Though employed in an advisory capacity, Thomson had, during
5292-410: The adulation. Thomson, along with the other principals of the project, was knighted on 10 November 1866. To exploit his inventions for signalling on long submarine cables, Thomson entered into a partnership with C. F. Varley and Fleeming Jenkin . In conjunction with the latter, he also devised an automatic curb sender , a kind of telegraph key for sending messages on a cable. Thomson took part in
5400-434: The atmosphere, while creating nitrogen oxide and ozone at the same time. Lightning is also the major cause of wildfire, and wildfire can contribute to climate change as well. More studies are warranted to clarify their relationship. The details of the charging process are still being studied by scientists, but there is general agreement on some of the basic concepts of thunderstorm electrification. Electrification can be by
5508-652: The atmospheric electric field. Thomson's water dropper electrometer was used for measuring the atmospheric electric field at Kew Observatory and Eskdalemuir Observatory for many years, and one was still in use operationally at the Kakioka Observatory in Japan until early 2021. Thomson may have unwittingly observed atmospheric electrical effects caused by the Carrington event (a significant geomagnetic storm) in early September 1859. Between 1870 and 1890
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#17327719604975616-401: The attachment process in progress. Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, there is a large drop in resistance across the lightning channel. Electrons accelerate rapidly as a result in a zone beginning at the point of attachment, which expands across the entire leader network at up to one third of
5724-645: The attention of the project's undertakers. In December 1856, he was elected to the board of directors of the Atlantic Telegraph Company. Thomson became scientific adviser to a team with Whitehouse as chief electrician and Sir Charles Tilston Bright as chief engineer, but Whitehouse had his way with the specification, supported by Faraday and Samuel F. B. Morse . Thomson sailed on board the cable-laying ship HMS Agamemnon in August 1857, with Whitehouse confined to land owing to illness, but
5832-671: The board of the British company Kodak Limited, affiliated with Eastman Kodak . In 1904 he became chancellor of the University of Glasgow . Kelvin resided in Netherhall, a redstone mansion in Largs , which he built in the 1870s and where he died in 1907. The Hunterian Museum at the University of Glasgow has a permanent exhibition on the work of Kelvin, which includes many of his original papers, instruments, and other artefacts, including his smoking pipe. Thomson's father, James Thomson ,
5940-476: The board that using purer copper for replacing the lost section of cable would improve data capacity, that he first made a difference to the execution of the project. The board insisted that Thomson join the 1858 cable-laying expedition, without any financial compensation, and take an active part in the project. In return, Thomson secured a trial for his mirror galvanometer, which the board had been unenthusiastic about, alongside Whitehouse's equipment. Thomson found
6048-683: The boys were tutored in French in Paris. Much of Thomson's life during the mid-1840s was spent in Germany and the Netherlands . Language study was given a high priority. His sister, Anna Thomson, was the mother of physicist James Thomson Bottomley FRSE. Thomson attended the Royal Belfast Academical Institution, where his father was a professor in the university department. In 1834, aged 10, he began studying at
6156-446: The cable must be "abandoned as being practically and commercially impossible". Thomson attacked Whitehouse's contention in a letter to the popular Athenaeum magazine, pitching himself into the public eye. Thomson recommended a larger conductor with a larger cross section of insulation . He thought Whitehouse no fool and suspected that he might have the practical skill to make the existing design work. Thomson's work had attracted
6264-459: The cable-laying expedition of the SS ; Great Eastern , but the voyage was dogged by technical problems. The cable was lost after 1,200 miles (1,900 km) had been laid, and the project was abandoned. A further attempt in 1866 laid a new cable in two weeks, and then recovered and completed the 1865 cable. The enterprise was feted as a triumph by the public, and Thomson enjoyed a large share of
6372-427: The case of biased percolation, describes random connectivity phenomena, which produce an evolution of connected structures similar to that of lightning strikes. A streamer avalanche model has recently been favored by observational data taken by LOFAR during storms. When a stepped leader approaches the ground, the presence of opposite charges on the ground enhances the strength of the electric field . The electric field
6480-444: The celebrated Henri Victor Regnault , at Paris; but in 1846 he was appointed to the chair of natural philosophy in the University of Glasgow. At age 22 he found himself wearing the gown of a professor in one of the oldest universities in the country and lecturing to the class of which he was a first year student a few years before. By 1847, Thomson had already gained a reputation as a precocious and maverick scientist when he attended
6588-515: The cloud to the ground's surface. The actual discharge is the final stage of a very complex process. At its peak, a typical thunderstorm produces three or more strikes to the Earth per minute. Lightning primarily occurs when warm air is mixed with colder air masses, resulting in atmospheric disturbances necessary for polarizing the atmosphere. Lightning can also occur during dust storms , forest fires , tornadoes , volcanic eruptions , and even in
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#17327719604976696-476: The clouds. Also, given the very low probability of lightning striking the same point repeatedly and consistently, scientific inquiry is difficult even in areas of high CG frequency. In a process not well understood, a bidirectional channel of ionized air, called a " leader ", is initiated between oppositely-charged regions in a thundercloud. Leaders are electrically conductive channels of ionized gas that propagate through, or are otherwise attracted to, regions with
6804-417: The cold of winter, where the lightning is known as thundersnow . Hurricanes typically generate some lightning, mainly in the rainbands as much as 160 km (99 mi) from the center. Lightning is not distributed evenly around Earth . On Earth, the lightning frequency is approximately 44 (± 5) times per second, or nearly 1.4 billion flashes per year and the median duration is 0.52 seconds made up from
6912-430: The combination of temperature and rapid upward air movement produces a mixture of super-cooled cloud droplets (small water droplets below freezing), small ice crystals, and graupel (soft hail). The updraft carries the super-cooled cloud droplets and very small ice crystals upward. At the same time, the graupel, which is considerably larger and denser, tends to fall or be suspended in the rising air. The differences in
7020-492: The conversion of heat into work was still outstanding. As soon as Joule read the paper he wrote to Thomson with his comments and questions. Thus began a fruitful, though largely epistolary, collaboration between the two men, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856, its discoveries including the Joule–Thomson effect , sometimes called
7128-435: The description of motion without regard to force . The text developed dynamics in various areas but with constant attention to energy as a unifying principle. A second edition appeared in 1879, expanded to two separately bound parts. The textbook set a standard for early education in mathematical physics . Thomson made significant contributions to atmospheric electricity for the relatively short time for which he worked on
7236-429: The first mathematical development of Michael Faraday 's idea that electric induction takes place through an intervening medium, or " dielectric ", and not by some incomprehensible "action at a distance". He also devised the mathematical technique of electrical images, which became a powerful agent in solving problems of electrostatics , the science which deals with the forces between electrically charged bodies at rest. It
7344-506: The following lines from Alexander Pope 's " An Essay on Man ". These lines inspired Thomson to understand the natural world using the power and method of science: Go, wondrous creature! mount where Science guides; Go measure earth, weigh air, and state the tides; Instruct the planets in what orbs to run, Correct old Time, and regulate the sun; Thomson became intrigued with Joseph Fourier's Théorie analytique de la chaleur ( The Analytical Theory of Heat ) and committed himself to study
7452-524: The ground and tops up to 15 km (9.3 mi) in height. The place on Earth where lightning occurs most often is over Lake Maracaibo , wherein the Catatumbo lightning phenomenon produces 250 bolts of lightning a day. This activity occurs on average, 297 days a year. The second most lightning density is near the village of Kifuka in the mountains of the eastern Democratic Republic of the Congo , where
7560-493: The ground, the proportion of CG strikes (versus CC or IC discharges) becomes greater when the cloud is closer to the ground. In the tropics, where the freezing level is generally higher in the atmosphere, only 10% of lightning flashes are CG. At the latitude of Norway (around 60° North latitude), where the freezing elevation is lower, 50% of lightning is CG. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2 km (0.62–1.24 mi) above
7668-402: The ground. Called step potentials, they are responsible for more injuries and deaths in groups of people or of other animals than the strike itself. Electricity takes every path available to it. Such step potentials will often cause current to flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes. The electric current of
7776-685: The initial return stroke. Each subsequent stroke usually re-uses the discharge channel taken by the previous one, but the channel may be offset from its previous position as wind displaces the hot channel. Natural phenomenon A natural phenomenon is an observable event which is not man-made. Examples include: sunrise , weather , fog , thunder , tornadoes ; biological processes , decomposition , germination ; physical processes , wave propagation , erosion ; tidal flow , and natural disasters such as electromagnetic pulses , volcanic eruptions , hurricanes and earthquakes . Over many intervals of time, natural phenomena have been observed by
7884-438: The ionic channel takes a comparatively long amount of time (hundreds of milliseconds ) in comparison to the resulting discharge, which occurs within a few dozen microseconds. The electric current needed to establish the channel, measured in the tens or hundreds of amperes , is dwarfed by subsequent currents during the actual discharge. Initiation of the lightning leader is not well understood. The electric field strength within
7992-752: The laying of the French Atlantic submarine communications cable of 1869, and with Jenkin was engineer of the Western and Brazilian and Platino-Brazilian cables, assisted by vacation student James Alfred Ewing . He was present at the laying of the Pará to Pernambuco section of the Brazilian coast cables in 1873. Thomson's wife, Margaret, died on 17 June 1870, and he resolved to make changes in his life. Already addicted to seafaring, in September he purchased
8100-403: The lead of Thomson and Tait, the branch of topology called knot theory was developed. Thomson's initiative in this complex study that continues to inspire new mathematics has led to persistence of the topic in history of science . Thomson was an enthusiastic yachtsman, his interest in all things relating to the sea perhaps arising from, or fostered by, his experiences on the Agamemnon and
8208-408: The leaders can be readily observed in slow-motion videos of lightning flashes. It is possible for one end of the leader to fill the oppositely-charged well entirely while the other end is still active. When this happens, the leader end which filled the well may propagate outside of the thundercloud and result in either a cloud-to-air flash or a cloud-to-ground flash. In a typical cloud-to-ground flash,
8316-445: The loss cannot be precisely compensated and I think it probable that it is under-compensated. Compensation would require a creative act or an act possessing similar power , resulting in a rejuvenating universe (as Thomson had previously compared universal heat death to a clock running slower and slower, although he was unsure whether it would eventually reach thermodynamic equilibrium and stop for ever ). Thomson also formulated
8424-434: The lower part of the storm. The result is that the upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. The upward motions within the storm and winds at higher levels in the atmosphere tend to cause the small ice crystals (and positive charge) in the upper part of the thunderstorm cloud to spread out horizontally some distance from
8532-416: The movement of the precipitation cause collisions to occur. When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged; see Figure 2. The updraft carries the positively charged ice crystals upward toward the top of the storm cloud. The larger and denser graupel is either suspended in the middle of the thunderstorm cloud or falls toward
8640-426: The negative leader's connection with the ground. Positive leaders decay more rapidly than negative leaders do. For reasons not well understood, bidirectional leaders tend to initiate on the tips of the decayed positive leaders in which the negative end attempts to re-ionize the leader network. These leaders, also called recoil leaders , usually decay shortly after their formation. When they do manage to make contact with
8748-419: The next 17 years Thomson was distracted by her suffering. On 16 October 1854, George Gabriel Stokes wrote to Thomson to try to re-interest him in work by asking his opinion on some experiments of Faraday on the proposed transatlantic telegraph cable . Faraday had demonstrated how the construction of a cable would limit the rate at which messages could be sent—in modern terms, the bandwidth . Thomson jumped at
8856-491: The previous distance record (southern Brazil, October 31, 2018). A single flash in Uruguay and northern Argentina on June 18, 2020, lasted for 17.1 seconds—0.37 seconds longer than the previous record (March 4, 2019, also in northern Argentina). In order for an electrostatic discharge to occur, two preconditions are necessary: first, a sufficiently high potential difference between two regions of space must exist, and second,
8964-412: The problem and published his response that month. He expressed his results in terms of the data rate that could be achieved and the economic consequences in terms of the potential revenue of the transatlantic undertaking. In a further 1855 analysis, Thomson stressed the impact that the design of the cable would have on its profitability. Thomson contended that the signalling speed through a given cable
9072-470: The return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a ground-to-cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 100,000 km/s (one-third of
9180-402: The speed of light). The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 27,800 °C (50,000 °F), causing it to radiate with
9288-412: The speed of light. This is the "return stroke" and it is the most luminous and noticeable part of the lightning discharge. A large electric charge flows along the plasma channel, from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of
9396-465: The subject, around 1859. He developed several instruments for measuring the atmospheric electric field, using some of the electrometers he had initially developed for telegraph work, which he tested at Glasgow and whilst on holiday on Arran. His measurements on Arran were sufficiently rigorous and well-calibrated that they could be used to deduce air pollution from the Glasgow area, through its effects on
9504-564: The thundercloud is not typically large enough to initiate this process by itself. Many hypotheses have been proposed. One hypothesis postulates that showers of relativistic electrons are created by cosmic rays and are then accelerated to higher velocities via a process called runaway breakdown . As these relativistic electrons collide and ionize neutral air molecules, they initiate leader formation. Another hypothesis involves locally enhanced electric fields being formed near elongated water droplets or ice crystals. Percolation theory , especially for
9612-494: The thunderstorm cloud base. This part of the thunderstorm cloud is called the anvil. While this is the main charging process for the thunderstorm cloud, some of these charges can be redistributed by air movements within the storm (updrafts and downdrafts). In addition, there is a small but important positive charge buildup near the bottom of the thunderstorm cloud due to the precipitation and warmer temperatures. The induced separation of charge in pure liquid water has been known since
9720-432: The time scales involved in thunderstorms. The charge carrier in lightning is mainly electrons in a plasma. The process of going from charge as ions (positive hydrogen ion and negative hydroxide ion) associated with liquid water or solid water to charge as electrons associated with lightning must involve some form of electro-chemistry, that is, the oxidation and/or the reduction of chemical species. As hydroxide functions as
9828-405: The topographic variation that would result in atmospheric mixing, lightning is notably less frequent over the world's oceans than over land. The North and South Poles are limited in their coverage of thunderstorms and therefore result in areas with the least lightning. In general, CG lightning flashes account for only 25% of all total lightning flashes worldwide. Since the base of a thunderstorm
9936-555: The vortex atom theory, which purported that an atom was a vortex in the aether , was popular among British physicists and mathematicians. Thomson pioneered the theory, which was distinct from the 17th century vortex theory of René Descartes in that Thomson was thinking in terms of a unitary continuum theory, whereas Descartes was thinking in terms of three different types of matter, each relating respectively to emission, transmission, and reflection of light. About 60 scientific papers were written by approximately 25 scientists. Following
10044-457: The voyage ended after 380 miles (610 km) when the cable parted. Thomson contributed to the effort by publishing in the Engineer the whole theory of the stresses involved in the laying of a submarine communications cable , showing when the line is running out of the ship, at a constant speed in a uniform depth of water, it sinks in a slant or straight incline from the point where it enters
10152-425: The voyages, developed a real engineer's instincts and skill at practical problem-solving under pressure, often taking the lead in dealing with emergencies and being unafraid to assist in manual work. A cable was completed on 5 August. Thomson's fears were realised when Whitehouse's apparatus proved insufficiently sensitive and had to be replaced by Thomson's mirror galvanometer. Whitehouse continued to maintain that it
10260-407: The water to that where it touches the bottom. Thomson developed a complete system for operating a submarine telegraph that was capable of sending a character every 3.5 seconds. He patented the key elements of his system, the mirror galvanometer and the siphon recorder , in 1858. Whitehouse still felt able to ignore Thomson's many suggestions and proposals. It was not until Thomson convinced
10368-504: The year of Lord Kelvin's birth, used −267 as an estimate of the absolute zero temperature. Thomson used data published by Regnault to calibrate his scale against established measurements. In his publication, Thomson wrote: ... The conversion of heat (or caloric ) into mechanical effect is probably impossible, certainly undiscovered —But a footnote signalled his first doubts about the caloric theory, referring to Joule's very remarkable discoveries . Surprisingly, Thomson did not send Joule
10476-462: Was a British mathematician, mathematical physicist and engineer. Born in Belfast, he was the professor of Natural Philosophy at the University of Glasgow for 53 years, where he undertook significant research and mathematical analysis of electricity, was instrumental in the formulation of the first and second laws of thermodynamics , and contributed significantly to unifying physics , which
10584-526: Was a teacher of mathematics and engineering at the Royal Belfast Academical Institution and the son of a farmer. James Thomson married Margaret Gardner in 1817 and, of their children, four boys and two girls survived infancy. Margaret Thomson died in 1830 when William was six years old. William and his elder brother James were tutored at home by their father while the younger boys were tutored by their elder sisters. James
10692-483: Was able to make a generous provision for his favourite son's education and, in 1841, installed him, with extensive letters of introduction and ample accommodation, at Peterhouse, Cambridge . While at Cambridge, Thomson was active in sports, athletics and sculling , winning the Colquhoun Sculls in 1843. He took a lively interest in the classics, music, and literature; but the real love of his intellectual life
10800-540: Was established by the Board of Trade and the Atlantic Telegraph Company. Most of the blame for the cable's failure was found to rest with Whitehouse. The committee found that, though underwater cables were notorious in their lack of reliability , most of the problems arose from known and avoidable causes. Thomson was appointed one of a five-member committee to recommend a specification for a new cable. The committee reported in October 1863. In July 1865, Thomson sailed on
10908-501: Was his equipment that was providing the service and started to engage in desperate measures to remedy some of the problems. He fatally damaged the cable by applying 2,000 volts . When the cable failed completely Whitehouse was dismissed, though Thomson objected and was reprimanded by the board for his interference. Thomson subsequently regretted that he had acquiesced too readily to many of Whitehouse's proposals and had not challenged him with sufficient vigour. A joint committee of inquiry
11016-470: Was intended to benefit from the major share of his father's encouragement, affection and financial support and was prepared for a career in engineering. In 1832, his father was appointed professor of mathematics at Glasgow , and the family moved there in October 1833. The Thomson children were introduced to a broader cosmopolitan experience than their father's rural upbringing, spending mid-1839 in London, and
11124-428: Was intrigued but sceptical. Though he felt that Joule's results demanded theoretical explanation, he retreated into an even deeper commitment to the Carnot–Clapeyron school. He predicted that the melting point of ice must fall with pressure , otherwise its expansion on freezing could be exploited in a perpetuum mobile . Experimental confirmation in his laboratory did much to bolster his beliefs. In 1848, he extended
11232-602: Was inversely proportional to the square of the length of the cable. Thomson's results were disputed at a meeting of the British Association in 1856 by Wildman Whitehouse , the electrician of the Atlantic Telegraph Company . Whitehouse had possibly misinterpreted the results of his own experiments but was doubtless feeling financial pressure as plans for the cable were already well under way. He believed that Thomson's calculations implied that
11340-444: Was known before his work, Kelvin determined its correct value as approximately −273.15 degrees Celsius or −459.67 degrees Fahrenheit . The Joule–Thomson effect is also named in his honour. Kelvin worked closely with mathematics professor Hugh Blackburn in his work. He also had a career as an electrical telegraph engineer and inventor which propelled him into the public eye and earned him wealth, fame, and honours. For his work on
11448-456: Was partly in response to his encouragement that Faraday undertook the research in September 1845 that led to the discovery of the Faraday effect , which established that light and magnetic (and thus electric) phenomena were related. He was elected a fellow of St. Peter's (as Peterhouse was often called at the time) in June 1845. On gaining the fellowship, he spent some time in the laboratory of
11556-436: Was the pursuit of science. The study of mathematics, physics, and in particular, of electricity, had captivated his imagination. In 1845 Thomson graduated as second wrangler . He also won the first Smith's Prize , which, unlike the tripos , is a test of original research. Robert Leslie Ellis , one of the examiners, is said to have declared to another examiner "You and I are just about fit to mend his pens." In 1845, he gave
11664-524: Was then in its infancy of development as an emerging academic discipline. He received the Royal Society 's Copley Medal in 1883 and served as its president from 1890 to 1895. In 1892, he became the first scientist to be elevated to the House of Lords . Absolute temperatures are stated in units of kelvin in Lord Kelvin's honour. While the existence of a coldest possible temperature, absolute zero ,
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