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Monday, August 18, 2014

Nikola Tesla

Nikola Tesla

From Wikipedia, the free encyclopedia 

Nikola Tesla
Tesla circa 1890.jpeg
Tesla, aged 34, 1890, photo by Napoleon Sarony
Born 10 July 1856
Smiljan, Austrian Empire (modern-day Croatia)
Died 7 January 1943 (aged 86)
New York City, New York, USA
Citizenship Austrian Empire (10 July 1856 – 1867)
United States (30 July 1891 – 7 January 1943)
Engineering career
Engineering discipline Electrical engineering
Mechanical engineering
Significant projects Alternating current,
high-voltage, high-frequency power experiments
Significant design Induction motor
Rotating magnetic field
Tesla coil
Radio remote control vehicle (torpedo)[1]:355
Significant awards
Signature TeslaSignature.svg

Nikola Tesla (Serbian Cyrillic: Никола Тесла; 10 July 1856 – 7 January 1943) was a Serbian American[2][3][4][5] inventor, electrical engineer, mechanical engineer, and futurist best known for his contributions to the design of the modern alternating current (AC) electricity supply system.[6]

Tesla gained experience in telephony and electrical engineering before immigrating to the United States in 1884 to work for Thomas Edison in New York City. He soon struck out on his own with financial backers, setting up laboratories and companies to develop a range of electrical devices. His patented AC induction motor and transformer were licensed by George Westinghouse, who also hired Tesla for a short time as a consultant. His work in the formative years of electric power development was also involved in the corporate struggle between making alternating current or direct current the power transmission standard, referred to as the war of currents. Tesla went on to pursue his ideas of wireless lighting and electricity distribution in his high-voltage, high-frequency power experiments in New York and Colorado Springs and made early (1893) pronouncements on the possibility of wireless communication with his devices. He tried to put these ideas to practical use in his ill-fated attempt at intercontinental wireless transmission; his unfinished Wardenclyffe Tower project.[7] In his lab he also conducted a range of experiments with mechanical oscillator/generators, electrical discharge tubes, and early X-ray imaging. He even built a wireless controlled boat which may have been the first such device ever exhibited.

Tesla was renowned for his achievements and showmanship, eventually earning him a reputation in popular culture as an archetypal "mad scientist."[8] His patents earned him a considerable amount of money, much of which was used to finance his own projects with varying degrees of success.[9]:121,154 He lived most of his life in a series of New York hotels, through his retirement. He died on 7 January 1943.[10]

Tesla's work fell into relative obscurity after his death, but in 1960 the General Conference on Weights and Measures named the SI unit of magnetic field strength the tesla in his honor.[11] Tesla has experienced a resurgence in interest in popular culture since the 1990s.[12]

Early years (1856–1885)


Tesla wearing a folk costume, c. 1880.

Rebuilt, Tesla's house (parish hall) in Smiljan, Croatia, where he was born, and the rebuilt church, where his father served. During the Yugoslav Wars, several of the buildings were severely damaged by fire. They were restored and reopened in 2006.[13]

Tesla's baptismal record, 28 June 1856.

Nikola Tesla's father Milutin, Orthodox priest in the village of Smiljan.

Nikola Tesla was born on 10 July (O.S. 28 June) 1856 to Serbian parents in the village of Smiljan, Austrian Empire (modern-day Croatia).[14][15] His father, Milutin Tesla, was an Orthodox priest.[5] Tesla's mother, Đuka Tesla (née Mandić), whose father was also an Orthodox priest,[14]:10 had a talent for making home craft tools, mechanical appliances, and the ability to memorize Serbian epic poems. Đuka had never received a formal education. Nikola credited his eidetic memory and creative abilities to his mother's genetics and influence.[9][16] Tesla's progenitors were from western Serbia, near Montenegro.[14]:12

Tesla was the fourth of five children. He had an older brother named Dane and three sisters, Milka, Angelina and Marica. Dane was killed in a horse-riding accident when Nikola was five.[17] In 1861, Tesla attended the "Lower" or "Primary" School in Smiljan where he studied German, arithmetic, and religion.[18] In 1862, the Tesla family moved to Gospić, Austrian Empire, where Tesla's father worked as a pastor. Nikola completed "Lower" or "Primary" School, followed by the "Lower Real Gymnasium" or "Normal School."[19]

In 1870, Tesla moved to Karlovac to attend school at Higher Real Gymnasium, where he was profoundly influenced by a math teacher Martin Sekulić.[14]:32[20] Tesla was able to perform integral calculus in his head, which prompted his teachers to believe that he was cheating.[21] He finished a four-year term in three years, graduating in 1873.[14]:33

In 1873, Tesla returned to his birthtown, Smiljan. Shortly after he arrived, Tesla contracted cholera; he was bedridden for nine months and was near death multiple times. Tesla's father, in a moment of despair, promised to send him to the best engineering school if he recovered from the illness[20][22] (his father had originally wanted him to enter the priesthood).[23]

In 1874, Tesla evaded being drafted into the Austro-Hungarian Army in Smiljan[24] by running away to Tomingaj, near Gračac. There, he explored the mountains in hunter's garb. Tesla claimed that this contact with nature made him stronger, both physically and mentally.[20] He read many books while in Tomingaj, and later claimed that Mark Twain's works had helped him to miraculously recover from his earlier illness.[22]

In 1875, Tesla enrolled at Austrian Polytechnic in Graz, Austria, on a Military Frontier scholarship. During his first year, Tesla never missed a lecture, earned the highest grades possible, passed nine exams[20][22] (nearly twice as many required[14]), started a Serbian culture club,[20] and even received a letter of commendation from the dean of the technical faculty to his father, which stated, "Your son is a star of first rank."[14] Tesla claimed that he worked from 3 a.m. to 11 p.m., no Sundays or holidays excepted.[22] He was "mortified when [his] father made light of [those] hard won honors." After his father's death in 1879,[24] Tesla found a package of letters from his professors to his father, warning that unless he were removed from the school, Tesla would be killed through overwork.[22]
During his second year, Tesla came into conflict with Professor Poeschl over the Gramme dynamo, when Tesla suggested that commutators weren't necessary. At the end of his second year, Tesla lost his scholarship and became addicted to gambling.[20][22] During his third year, Tesla gambled away his allowance and his tuition money, later gambling back his initial losses and returning the balance to his family. Tesla claimed that he "conquered [his] passion then and there," but later he was known to play billiards in the US. When exam time came, Tesla was unprepared and asked for an extension to study, but was denied. He never graduated from the university and did not receive grades for the last semester.[24]

In December 1878, Tesla left Graz and severed all relations with his family to hide the fact that he dropped out of school.[24] His friends thought that he had drowned in the Mur River.[25] Tesla went to Maribor (now in Slovenia), where he worked as a draftsman for 60 florins a month. He spent his spare time playing cards with local men on the streets.[24] In March 1879, Milutin Tesla went to Maribor to beg his son to return home, but Nikola refused.[26] Nikola suffered a nervous breakdown at around the same time.[25]

Tesla aged 23, c. 1879

On 24 March 1879, Tesla was returned to Gospić under police guard for not having a residence permit. On 17 April 1879, Milutin Tesla died at the age of 60 after contracting an unspecified illness[27] (although some sources claim that he died of a stroke[28] ). During that year, Tesla taught a large class of students in his old school, Higher Real Gymnasium, in Gospić.[27]

In January 1880, two of Tesla's uncles put together enough money to help him leave Gospić for Prague where he was to study. Unfortunately, he arrived too late to enroll at Charles-Ferdinand University; he never studied Greek, a required subject; and he was illiterate in Czech, another required subject. Tesla did, however, attend lectures at the university, although, as an auditor, he did not receive grades for the courses.[29][30][31]

In 1881, Tesla moved to Budapest to work under Ferenc Puskas at a telegraph company, the Budapest Telephone Exchange. Upon arrival, Tesla realized that the company, then under construction, was not functional, so he worked as a draftsman in the Central Telegraph Office instead. Within a few months, the Budapest Telephone Exchange became functional and Tesla was allocated the chief electrician position.[32] During his employment, Tesla made many improvements to the Central Station equipment and claimed to have perfected a telephone repeater or amplifier, which was never patented nor publicly described.[22]

Working for Edison

In 1882, Tesla began working for the Continental Edison Company in France, designing and making improvements to electrical equipment.[33] In June 1884, he relocated to New York City[14]:57–60[34] where he was hired by Thomas Edison to work for his Edison Machine Works. Tesla's work for Edison began with simple electrical engineering and quickly progressed to solving more difficult problems.[35]

Tesla was offered the task of completely redesigning the Edison Company's direct current generators. In 1885, he claimed that he could redesign Edison's inefficient motor and generators, making an improvement in both service and economy. According to Tesla, Edison remarked, "There's fifty thousand dollars in it for you—if you can do it"[9]:54–57—this has been noted as an odd statement from an Edison whose company was stingy with pay and who did not have that sort of cash on hand.[1]:110 After months of work, Tesla fulfilled the task and inquired about payment. Edison, claiming that he was only joking, replied, "Tesla, you don't understand our American humor."[14]:64[36] Instead, Edison offered a US$10 a week raise over Tesla's US$18 per week salary; Tesla refused the offer and immediately resigned.[9]

Middle years (1886–1899)

After leaving Edison's company Tesla partnered with two businessmen in 1886, Robert Lane and Benjamin Vale, who agreed to finance an electric lighting company in Tesla's name, Tesla Electric Light & Manufacturing.[37] The company installed electrical arc light based illumination systems designed by Tesla and also had designs for dynamo electric machine commutators, the first patents issued to Tesla in the US.[1]

The investors showed little interest in Tesla's ideas for new types of motors and electrical transmission equipment and also seemed to think it was better to develop an electrical utility than invent new systems.[38] They eventually forced Tesla out leaving him penniless. He even lost control of the patents he had generated since he had assigned them to the company in lieu of stock.[38] He had to work at various electrical repair jobs and even as a ditch digger for $2 per day. Tesla considered the winter of 1886/1887 as a time of "terrible headaches and bitter tears." During this time, he questioned the value of his education.[1][39]

AC and the induction motor


Drawing from U.S. Patent 381,968, illustrating principle of Tesla's alternating current induction motor

In late 1886 Tesla met Alfred S. Brown, a Western Union superintendent, and New York attorney Charles F. Peck. The two men were experienced in setting up companies and promoting inventions and patents for financial gain.[40] Based on Tesla's patents and other ideas they agreed to financially back him and handle his patents. Together in April 1887 they formed the Tesla Electric Company with an agreement that profits from generated patents would go 1/3 to Tesla, 1/3 to Peck and Brown, and 1/3 to fund development.[40] They set up a laboratory for Tesla at 89 Liberty Street in Manhattan where he worked on improving and developing new types of electric motors, generators and other devices.

One of the things Tesla developed at that laboratory in 1887 was an induction motor that ran on alternating current, a power system format that was starting to be built in Europe and the US because its advantages in long distance high voltage transmission. The motor used polyphase current which generated a rotating magnetic field to turn the motor (a principle Tesla claimed to have conceived of in 1882).[41][42][43] This innovative electric motor, patented in May 1888, was a simple self-starting design that did not need a commutator, thus avoiding sparking and the high maintenance of constantly servicing and replacing mechanical brushes.[1]:161[44]

In 1888, the editor of Electrical World magazine, Thomas Commerford Martin (a friend and publicist), arranged for Tesla to demonstrate his alternating current system, including his induction motor, at the American Institute of Electrical Engineers (now IEEE).[45] Engineers working for the Westinghouse Electric & Manufacturing Company reported to George Westinghouse that Tesla had a viable AC motor and related power system—something that Westinghouse had been trying to secure the patents to. Westinghouse looked into getting a patent on a similar commutatorless rotating magnetic field based induction motor presented in a paper in March 1888 by the Italian physicist Galileo Ferraris but decided Tesla's patent would probably control the market.[1]:160–162[46]

Nikola Tesla's AC dynamo-electric machine (AC Electric generator) in an 1888 U.S. Patent 390,721.

In July 1888, Brown and Peck negotiated a licensing deal with George Westinghouse for Tesla's polyphase induction motor and transformer designs for $60,000 in cash and stock and a royalty of $2.50 per AC horsepower produced by each motor. Westinghouse also hired Tesla for one year for the large fee of $2,000 ($52,500 in today's dollars[47]) per month to be a consultant at the Westinghouse Electric & Manufacturing Company's Pittsburgh labs.[48]

During that year, Tesla worked in Pittsburgh, helping to create an alternating current system to power the city's streetcars. He found the time there frustrating because of conflicts between him and the other Westinghouse engineers over how best to implement AC power. Between them, they settled on a 60-cycle AC current system Tesla proposed (to match the working frequency of Tesla's motor), although they soon found that, since Tesla's induction motor could only run at a constant speed, it would not work for street cars. They ended up using a DC traction motor instead.[49][50]

War of Currents

Tesla's alternating current work put him firmly on the "AC" side of the so-called "War of Currents,"[51] an electrical standards battle waged between Thomas Edison and George Westinghouse.[52][53] Tesla's patents, along with the others that Westinghouse's company had acquired or developed, allowed Westinghouse to build a rival AC system that could compete with Thomas Edison's DC system.[54]

In 1893, George Westinghouse won the bid to electrify the 1893 World's Columbian Exposition in Chicago with alternating current, beating out a bid by Edison to electrify the fair with direct current. This World's Fair devoted a building to electrical exhibits. It was a key event in the history of AC power, as Westinghouse demonstrated the safety, reliability, and efficiency of alternating current to the American public.[55][56] At the Columbian Exposition, Tesla demonstrated a series of electrical effects previously performed throughout America and Europe,[9]:76 included using high-voltage, high-frequency alternating current to light a wireless gas-discharge lamp.[9]:79 An observer noted:
Within the room was suspended two hard-rubber plates covered with tin foil. These were about fifteen feet apart, and served as terminals of the wires leading from the transformers. When the current was turned on, the lamps or tubes, which had no wires connected to them, but lay on a table between the suspended plates, or which might be held in the hand in almost any part of the room, were made luminous. These were the same experiments and the same apparatus shown by Tesla in London about two years previous, "where they produced so much wonder and astonishment".[57]
Tesla also explained the principles of a rotating magnetic field and induction motor by demonstrating how to make a copper egg stand on end using a device he constructed known as the Egg of Columbus.[58]

By 1892 Edison's company was consolidated into the conglomerate General Electric by financier J. P. Morgan and the new company (by then switching over to an all AC system) was involved in take over attempts and patent battles with Westinghouse Electric. Although a patent sharing agreement was signed between the two companies in 1896[59] Westinghouse was still cashed strapped from the financial warfare. To secure further loans Westinghouse was forced to revisit Tesla's AC patent, which bankers considered a financial strain on the company[60][61] (at that point Westinghouse had paid out an estimated $200,000 in licenses and royalties to Tesla, Brown, and Peck[62]). In 1897, Westinghouse explained his financial difficulties to Tesla in stark terms, saying that if things continue the way they were he would no longer be in control of Westinghouse Electric and Tesla would have to "deal with the bankers" to try to collect future royalties. Westinghouse convinced Tesla to release his company from the licensing agreement over Tesla's AC patents in exchange for Westinghouse Electric purchasing the patents for a lump sum payment of $216,000;[9]:73–74 this provided Westinghouse a break from what, due to alternating current's rapid gain in popularity, had turned out to be an overly generous $2.50 per AC horsepower royalty.[48]

American citizenship

On 30 July 1891, at the age of 35, Tesla became a naturalized citizen of the United States,[63] and established his South Fifth Avenue laboratory, and later another at 46 E. Houston Street, in New York. He lit electric lamps wirelessly at both locations, demonstrating the potential of wireless power transmission.[64] In the same year, he patented the Tesla coil.[65]

Tesla served as vice president of the American Institute of Electrical Engineers, the forerunner (along with the Institute of Radio Engineers) of the modern-day IEEE, from 1892 to 1894.[66]

X-ray experimentation


X-ray of a hand taken by Tesla.

Starting in 1894, Tesla began investigating what he referred to as radiant energy of "invisible" kinds when he had noticed damaged film in his lab in previous experiments[67][68] (later identified as "Roentgen rays" or "X-Rays"). His early experiments were with Crookes tubes, a cold cathode electrical discharge tube. Soon after, much of Tesla's early research—hundreds of invention models, plans, notes, laboratory data, tools, photographs, valued at $50,000—was lost in the 5th Avenue laboratory fire of March 1895. Tesla is quoted by The New York Times as saying, "I am in too much grief to talk. What can I say?"[69] Tesla may have inadvertently captured an X-ray image (predating Wilhelm Röntgen's December 1895 announcement of the discovery of x-rays by a few weeks) when he tried to photograph Mark Twain illuminated by a Geissler tube, an earlier type of gas discharge tube. The only thing captured in the image was the metal locking screw on the camera lens.[9]:134

In March 1896, after hearing of Wilhelm Röntgen's discovery of X-ray and X-ray imaging (radiography),[70] Tesla proceeded to do his own experiments in X-ray imaging, developing a high energy single terminal vacuum tube of his own design that had no target electrode and that worked from the output of the Tesla Coil (the modern term for the phenomenon produced by this device is bremsstrahlung or braking radiation). In his research, Tesla devised several experimental setups to produce X-rays. Tesla held that, with his circuits, the "instrument will ... enable one to generate Roentgen rays of much greater power than obtainable with ordinary apparatus."[71]

Tesla noted the hazards of working with his circuit and single-node X-ray-producing devices. In his many notes on the early investigation of this phenomenon, he attributed the skin damage to various causes. He believed early on that damage to the skin was not caused by the Roentgen rays, but by the ozone generated in contact with the skin, and to a lesser extent, by nitrous acid. Tesla incorrectly believed that X-rays were longitudinal waves, such as those produced in waves in plasma. These plasma waves can occur in force-free magnetic fields.[72][73]

On 11 July 1934, the New York Herald Tribune published an article on Tesla, in which he recalled an event that would occasionally take place while experimenting with his single-electrode vacuum tubes; a minute particle would break off the cathode, pass out of the tube, and physically strike him. "Tesla said he could feel a sharp stinging pain where it entered his body, and again at the place where it passed out." In comparing these particles with the bits of metal projected by his "electric gun," Tesla said, "The particles in the beam of force ... will travel much faster than such particles ... and they will travel in concentrations."[74]

Radio


Wireless transmission of power and energy demonstration during his 1891 lecture on high frequency and potential.

Tesla's theories on the possibility of the transmission by radio waves go back as far as lectures and demonstrations in 1893 in St. Louis, Missouri, the Franklin Institute in Philadelphia, Pennsylvania, and the National Electric Light Association.[75] Tesla's demonstrations and principles were written about widely through various media outlets.[76] Many devices such as the Tesla Coil were used in the further development of radio.[77]
In 1898, Tesla demonstrated a radio-controlled boat (U.S. Patent 613,809 —Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles).

Tesla's radio wave experiments in 1896 were conducted in Gerlach Hotel (later renamed The Radio Wave building), where he resided.[78]

In 1898, Tesla demonstrated a radio-controlled boat—which he dubbed "teleautomaton"—to the public during an electrical exhibition at Madison Square Garden.[1] The crowd that witnessed the demonstration made outrageous claims about the workings of the boat, such as magic, telepathy, and being piloted by a trained monkey hidden inside.[79] Tesla tried to sell his idea to the U.S. military as a type of radio-controlled torpedo, but they showed little interest.[80] Remote radio control remained a novelty until World War I and afterward, when a number of countries used it in military programs.[81] Tesla took the opportunity to further demonstrate "Teleautomatics" in an address to a meeting of the Commercial Club in Chicago, whilst he was travelling to Colorado Springs, on 13 May 1899.[18]

In 1900, Tesla was granted patents for a "system of transmitting electrical energy" and "an electrical transmitter." When Guglielmo Marconi made his famous first-ever transatlantic radio transmission in 1901, Tesla quipped that it was done with 17 Tesla patents. This was the beginning of years of patent battles over radio with Tesla's patents being upheld in 1903, followed by a reverse decision in favor of Marconi in 1904. In 1943, a Supreme Court of the United States decision restored the prior patents of Tesla, Oliver Lodge, and John Stone.[82] The court declared that their decision had no bearing on Marconi's claim as the first to achieve radio transmission, just that since Marconi's claim to certain patents were questionable, he could not claim infringement on those same patents[83] (there are claims the high court was trying to nullify a World War I claim against the U.S. government by the Marconi Company via simply restoring Tesla's prior patent).[82]

Colorado Springs


Multiple exposure publicity picture of Tesla sitting in his Colorado Springs laboratory with his "Magnifying transmitter" generating millions of volts and producing 7-metre (23 ft) long arcs.

An experiment in Colorado Springs. This bank of lights is receiving power by means of electrodynamic induction from an oscillator 100 feet (30 m) from the bulbs

A Colorado Springs experiment: here a grounded tuned coil in resonance with a distant transmitter illuminates a light near the bottom of the picture.

On 17 May 1899, Tesla moved to Colorado Springs, where he would have room for his high-voltage, high-frequency experiments;[18] his lab was located near Foote Ave. and Kiowa St.[84] He chose this location because the polyphase alternating current power distribution system had been introduced there and he had associates who were willing to give him all the power he needed without charging for it.[85] Upon his arrival, he told reporters that he was conducting wireless telegraphy experiments, transmitting signals from Pikes Peak to Paris.[citation needed] The 1978 book Colorado Springs Notes, 1899–1900 contains descriptions of Tesla's experiments.

On 15 June 1899, Tesla performed his first experiments at his Colorado Springs lab; he recorded his initial spark length at five inches long, but very thick and noisy.[18]

Tesla investigated atmospheric electricity, observing lightning signals via his receivers. Tesla stated that he observed stationary waves during this time.[86] The great distances and the nature of what Tesla was detecting from lightning storms confirmed his belief that the earth had a resonant frequency.[87][88]

He produced artificial lightning (with discharges consisting of millions of volts and up to 135 feet long).[89] Thunder from the released energy was heard 15 miles away in Cripple Creek, Colorado. People walking along the street observed sparks jumping between their feet and the ground. Sparks sprang from water line taps when touched. Light bulbs within 100 feet of the lab glowed even when turned off. Horses in a livery stable bolted from their stalls after receiving shocks through their metal shoes. Butterflies were electrified, swirling in circles with blue halos of St. Elmo's fire around their wings.[90]

While experimenting, Tesla inadvertently faulted a power station generator, causing a power outage. In August 1917, Tesla explained what had happened in The Electrical Experimenter: "As an example of what has been done with several hundred kilowatts of high frequency energy liberated, it was found that the dynamos in a power house six miles away were repeatedly burned out, due to the powerful high frequency currents set up in them, and which caused heavy sparks to jump through the windings and destroy the insulation!"[91]

During his time at his lab, Tesla observed unusual signals from his receiver which he concluded may be communications from another planet. He mentioned them in a letter to reporter Julian Hawthorne at the Philadelphia North American on December 8, 1899[92] and in a December 1900 letter about possible discoveries in the new century to the Red Cross Society where he referred to messages "from another world" that read "1... 2... 3...".[93][94] Reporters treated it as a sensational story and jumped to the conclusion Tesla was hearing signals from Mars.[95] He expanded on the signals he heard in a February 9, 1901 Collier's Weekly article "Talking With Planets" where he said it had not been immediately apparent to him that he was hearing "intelligently controlled signals" and that the signals could come from Mars, Venus, or other plants.[96] It has been hypothesized that he may have intercepted Marconi's European experiments in July of 1899—Marconi may have transmitted the letter S (dot/dot/dot) in a naval demonstration, the same three impulses that Tesla hinted at hearing in Colorado[97]—or signals from another experimenter in wireless transmission.[98]

In 1899, John Jacob Astor IV invested $100,000 for Tesla to further develop and produce a new lighting system. Instead, Tesla used the money to fund his Colorado Springs experiments.[99]

On 7 January 1900, Tesla left Colorado Springs.[citation needed] His lab was torn down in 1904, and its contents were sold two years later to satisfy a debt.[100][101]

The Colorado experiments had prepared Tesla for the establishment of the trans-Atlantic wireless telecommunications facility known as Wardenclyffe near Shoreham, Long Island.[102]

Wardenclyffe years (1900–1917)


Tesla Ready for Business – 7 August 1901 New-York tribune article

The Tesla coil wireless transmitter
U.S. Patent 1,119,732

Tesla's Wardenclyffe plant on Long Island in 1904. From this facility, Tesla hoped to demonstrate wireless transmission of electrical energy across the Atlantic.

In 1900, with $150,000 ($4,252,200 in today's dollars[47]; 51% from J. Pierpont Morgan), Tesla began planning the Wardenclyffe Tower facility.[103]

Tesla later approached Morgan to ask for more funds to build a more powerful transmitter. When asked where all the money had gone, Tesla responded by saying that he was affected by the Panic of 1901, which he (Morgan) had caused. Morgan was shocked by the reminder of his part in the stock market crash and by Tesla's breach of contract by asking for more funds. Tesla wrote another plea to Morgan, but it was also fruitless. Morgan still owed Tesla money on the original agreement, and Tesla had been facing foreclosure even before construction of the tower began.[98]

In December 1901, Marconi successfully transmitted the letter S from England to Newfoundland, terminating Tesla's relationship with Morgan.[improper synthesis?] Over the next five years, Tesla wrote over 50 letters to Morgan, pleading for and demanding additional funding to complete the construction of Wardenclyffe. Tesla continued the project for another nine months. The tower was erected to its full 187 feet (57 m).[98] In July 1903, Tesla wrote to Morgan that in addition to wireless communication, Wardenclyffe would be capable of wireless transmission of electric power.[103] On 14 October 1904, Morgan finally replied through his secretary, stating, "It will be impossible for [me] to do anything in the matter," after Tesla had written to Morgan when the financier was meeting with the Archbishop of Canterbury in an attempt to appeal to his Christian spirit.[98]

In June 1902, Tesla's lab operations were moved to Wardenclyffe from Houston Street.[103]
On his 50th birthday in 1906, Tesla demonstrated his 200 horsepower (150 kilowatts) 16,000 rpm bladeless turbine. During 1910–1911 at the Waterside Power Station in New York, several of his bladeless turbine engines were tested at 100–5,000 hp.[104]

Tesla invented a steam-powered mechanical oscillator—Tesla's oscillator. While experimenting with mechanical oscillators at his Houston Street lab, Tesla allegedly generated a resonance of several buildings. As the speed grew, it is said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to use a sledge hammer to terminate the experiment, just as the police arrived.[14]:162–164 In February 1912, an article—"Nikola Tesla, Dreamer" by Allan L. Benson—was published in World Today, in which an artist's illustration appears showing the entire earth cracking in half with the caption, "Tesla claims that in a few weeks he could set the earth's crust into such a state of vibration that it would rise and fall hundreds of feet and practically destroy civilization. A continuation of this process would, he says, eventually split the earth in two."[74]

Before World War I, Tesla sought overseas investors. After the war started, Tesla lost the funding he was receiving from his patents in European countries. Eventually, he sold Wardenclyffe for $20,000 ($470,900 in today's dollars[47]).[103] In 1917, around the time that the Wardenclyffe Tower was demolished by Boldt to make the land a more viable real estate asset, Tesla received AIEE's highest honor, the Edison Medal.[citation needed]

In the August 1917 edition of the magazine Electrical Experimenter Tesla postulated that electricity could be used to locate submarines via using the reflection of an "electric ray" of "tremendous frequency," with the signal being viewed on a fluorescent screen (a system that has been noted to have a superficial resemblance to modern RADAR).[105] Tesla was incorrect in his assumption that high frequency radio waves would penetrate water[106] but Émile Girardeau, who helped develop France's first RADAR system in the 1930s, noted in 1953 that Tesla's general speculation that a very strong high frequency signal would be needed was correct stating "(Tesla) was prophesying or dreaming, since he had at his disposal no means of carrying them out, but one must add that if he was dreaming, at least he was dreaming correctly."[9]:266[107]

Nobel Prize rumors

On 6 November 1915, a Reuters news agency report from London had the 1915 Nobel Prize in Physics awarded to Thomas Edison and Nikola Tesla; however, on 15 November, a Reuters story from Stockholm stated the prize that year was being awarded to Sir William Henry Bragg and William Lawrence Bragg "for their services in the analysis of crystal structure by means of X-rays."[9]:245[108][109] There were unsubstantiated rumors at the time that Tesla and/or Edison had refused the prize.[9]:245 The Nobel Foundation said, "Any rumor that a person has not been given a Nobel Prize because he has made known his intention to refuse the reward is ridiculous"; a recipient could only decline a Nobel Prize after he is announced a winner.[9]:245

There have been subsequent claims by Tesla biographers that Edison and Tesla were the original recipients and that neither was given the award because of their animosity toward each other; that each sought to minimize the other's achievements and right to win the award; that both refused ever to accept the award if the other received it first; that both rejected any possibility of sharing it; and even that a wealthy Edison refused it to keep Tesla from getting the $20,000 prize money.[9]:245[16][110]

In the years after these rumors, neither Tesla nor Edison won the prize (although Edison did receive one of 38 possible bids in 1915 and Tesla did receive one of 38 possible bids in 1937).[111]

Later years (1918–1943)

In 1928, Tesla received his last patent, U.S. Patent 1,655,114, for a biplane capable of taking off vertically (VTOL aircraft) and then be "gradually tilted through manipulation of the elevator devices" in flight until it was flying like a conventional plane.[112] Tesla thought the plane would sell for less than $1,000.[9]:251 Although the aircraft was probably impractical, it may be the earliest known design for what became the tiltrotor/tilt-wing concept as well as the earliest proposal for the use of turbine engines in rotor aircraft.[113][improper synthesis?]

Starting in 1934, the Westinghouse Electric & Manufacturing Company began paying Tesla $125 per month as well as paying his rent at the Hotel New Yorker, expenses the Company would pay for the rest of Tesla's life. Accounts on how this came about vary. Several sources say Westinghouse was worried about potential bad publicity surrounding the impoverished conditions their former star inventor was living under.[1]:365[114][115] It has been described as being couched in the form of a "consulting fee" to get around Tesla's aversion to accept charity, or by one biographer (Marc Seifer), as a type of unspecified settlement.[115]

In 1935, in an annual birthday celebration interview, Tesla announced a method of transmitting mechanical energy with minimal loss over any terrestrial distance, a related new means of communication, and a method of accurately determining the location of underground mineral deposits.[74]

In the fall of 1937, after midnight one night, Tesla left the Hotel New Yorker to make his regular commute to the cathedral and the library to feed the pigeons. While crossing a street a couple of blocks from the hotel, Tesla was unable to dodge a moving taxicab and was thrown heavily to the ground. Tesla's back was severely wrenched and three of his ribs were broken in the accident (the full extent of his injuries will never be known; Tesla refused to consult a doctor—an almost lifelong custom). Tesla didn't raise any question as to who was at fault and refused medical aid, only asking be taken to his hotel via cab. Tesla was bedridden for some months and was unable to continue feeding pigeons from his window; soon, they failed to come. In the spring of 1938, Tesla was able to get up. He at once resumed the pigeon-feeding walks on a much more limited scale, but frequently had a messenger act for him.[14]

Directed-energy weapon

Later in life, Tesla made claims concerning a "teleforce" weapon after studying the Van de Graaff generator.[116][117] The press called it a "peace ray" or death ray.[118][119] Tesla described the weapon as being able to be used against ground-based infantry or for antiaircraft purposes.
Tesla gives the following description concerning the particle gun's operation:
[The nozzle would] send concentrated beams of particles through the free air, of such tremendous energy that they will bring down a fleet of 10,000 enemy airplanes at a distance of 200 miles from a defending nation's border and will cause armies to drop dead in their tracks.[120][121]
In total, the components and methods included:
  • An apparatus for producing manifestations of energy in free air instead of in a high vacuum as in the past.
  • A mechanism for generating tremendous electrical force.
  • A means of intensifying and amplifying the force developed by the second mechanism.
  • A new method for producing a tremendous electrical repelling force. This would be the projector, or gun, of the invention.[122][123][124]
Tesla claimed to have worked on plans for a directed-energy weapon from the early 1900s until his death.[125][126]

In 1937, at a luncheon in his honor concerning the death ray, Tesla stated, "But it is not an experiment ... I have built, demonstrated and used it. Only a little time will pass before I can give it to the world." His records indicate that the device is based on a narrow stream of small tungsten pellets that are accelerated via high voltage (by means akin to his magnifying transformer).[117]

During the same year, Tesla wrote a treatise, The Art of Projecting Concentrated Non-dispersive Energy through the Natural Media,[127] concerning charged particle beam weapons.[128] Tesla published the document in an attempt to expound on the technical description of a "superweapon that would put an end to all war." This treatise is currently in the Nikola Tesla Museum archive in Belgrade. It describes an open-ended vacuum tube with a gas jet seal that allows particles to exit, a method of charging particles to millions of volts, and a method of creating and directing non-dispersive particle streams (through electrostatic repulsion).[128] Tesla tried to interest the US War Department,[129] the United Kingdom, the Soviet Union, and Yugoslavia in the device.[130]

During the period in which the negotiations were being carried on, Tesla claimed that efforts had been made to steal the invention. His room had been entered and his papers had been scrutinized, but the thieves, or spies, left empty-handed. He said that there was no danger that his invention could be stolen, for he had at no time committed any part of it to paper. The blueprint for the teleforce weapon was all in his mind.[131]

Death


Gilded urn with Tesla's ashes, in his favorite geometrical object, a sphere, Nikola Tesla Museum, Belgrade.

On 7 January 1943, Tesla, 86, died alone in room 3327 of the New Yorker Hotel. His body was later found by maid Alice Monaghan after she had entered Tesla's room, ignoring the "do not disturb" sign that Tesla had placed on his door two days earlier. Assistant medical examiner H.W. Wembly examined the body and ruled that the cause of death had been coronary thrombosis.[19] Tesla's remains were taken to the Frank E. Campbell Funeral Home at Madison Ave. and 81st St. A long-time friend and supporter of Tesla, Hugo Gernsback, commissioned a sculptor to create a death mask, now displayed in the Nikola Tesla Museum.[19]

Two days later, the FBI ordered the Alien Property Custodian to seize Tesla's belongings,[19] even though Tesla was an American citizen.[63] Tesla's entire estate from the Hotel New Yorker and other New York City hotels was transported to the Manhattan Storage and Warehouse Company under Office of Alien Property (OAP) seal.[19] John G. Trump, a professor at M.I.T. and well-known electrical engineer serving as a technical aide to the National Defense Research Committee, was called in to analyze the Tesla items in OAP custody.[19] After a three-day investigation, Trump's report concluded that there was nothing that would constitute a hazard in unfriendly hands, stating:
[Tesla's] thoughts and efforts during at least the past 15 years were primarily of a speculative, philosophical, and somewhat promotional character often concerned with the production and wireless transmission of power; but did not include new, sound, workable principles or methods for realizing such results.[132]
In a box purported to contain a part of Tesla's "death ray," Trump found a 45-year-old multidecade resistance box.[133]

On 10 January 1943, New York City mayor Fiorello La Guardia read a eulogy written by Slovene-American author Louis Adamic live over the WNYC radio while violin pieces "Ave Maria" and "Tamo daleko" were played in the background.[19] On 12 January 2,000 people attended a state funeral for Tesla at the Cathedral of Saint John the Divine. After the funeral, Tesla's body was taken to the Ferncliff Cemetery in Ardsley, New York, where it was later cremated. The following day, a second service was conducted by prominent priests in the Trinity Chapel (today's Serbian Orthodox Cathedral of Saint Sava) in New York City.[19]

Estate

In 1952, following pressure from Tesla's nephew, Sava Kosanović, Tesla's entire estate was shipped to Belgrade in 80 trunks marked N.T.[18] In 1957, Kosanović secretary Charlotte Muzar transported Tesla's ashes from the United States to Belgrade.[18] The ashes are displayed in a gold-plated sphere on a marble pedestal in the Nikola Tesla Museum.[134]

Despite having sold his AC electricity patents, Tesla died impoverished and in debt.[135][136][137][138]

Patents


Newspaper representation of Tesla's theoretical invention, the thought camera, which would photograph thoughts. Circa 1933.

Tesla obtained around 300 patents worldwide for his inventions.[139] Some of Tesla's patents are not accounted for, and various sources have discovered some that have lain hidden in patent archives. There are a minimum of 278 patents[139] issued to Tesla in 26 countries that have been accounted for. Many of Tesla's patents were in the United States, Britain, and Canada, but many other patents were approved in countries around the globe.[9]:62 Many inventions developed by Tesla were not put into patent protection.

Personal life 

Tesla worked every day from 9:00 a.m until 6:00 p.m. or later, with dinner from exactly 8:10 p.m., at Delmonico's restaurant and later the Waldorf-Astoria Hotel. Tesla would telephone his dinner order to the headwaiter, who also could be the only one to serve him. "The meal was required to be ready at eight o'clock ... He dined alone, except on the rare occasions when he would give a dinner to a group to meet his social obligations. Tesla would then resume his work, often until 3:00 a.m."[14]:283, 286

For exercise, Tesla walked between 8 to 10 miles per day. He squished his toes one hundred times for each foot every night, claiming that it stimulated his brain cells.[140]
In an interview with newspaper editor Arthur Brisbane, Tesla said that he did not believe in telepathy, stating, "Suppose I made up my mind to murder you," he said, "In a second you would know it. Now, isn't that wonderful? By what process does the mind get at all this?" In the same interview, Tesla said that he believed that all fundamental laws could be reduced to one.[141]

Near the end of his life, Tesla walked to the park every day to feed the pigeons and even brought injured ones into his hotel room to nurse back to health.[142][143] He claimed that he had been visited by a specific injured white pigeon daily. Tesla spent over $2,000, including building a device that comfortably supported her so her bones could heal, to fix her broken wing and leg.[24] Tesla stated,
I have been feeding pigeons, thousands of them for years. But there was one, a beautiful bird, pure white with light grey tips on its wings; that one was different. It was a female. I had only to wish and call her and she would come flying to me. I loved that pigeon as a man loves a woman, and she loved me. As long as I had her, there was a purpose to my life.[144][145]
Tesla became a vegetarian in his later years, living on only milk, bread, honey, and vegetable juices.[117][146]

Appearance


Tesla's portrait – Blue Portrait – from 1916, painted by then-Hungarian princess, Vilma Lwoff-Parlaghy.

Tesla, aged 40. c. 1896

Tesla was 6 ft 2 in (1.88 m) tall and weighed 142 pounds (64 kg), with almost no weight variance from 1888 to about 1926.[14]:292 He was an elegant, stylish figure in New York City, meticulous in his grooming, clothing, and regimented in his daily activities.
This was not because of personal vanity. Neatness and fastidiousness in clothes were entirely in harmony with every other phase of his personality. He did not maintain a large wardrobe and he wore no jewelry of any kind ... He observed, however, that in the matter of clothes the world takes a man at his own valuation, as expressed in his appearance, and frequently eases his way to his objective through small courtesies not extended to less prepossessing individuals.[14]:289
Although many of Tesla's progenitors were dark-eyed, his eyes were gray-blue. He claimed that his eyes were originally darker, but as a result of the exorbitant use of his brain, their hue changed. However, his mother and some of his cousins possessed gray eyes, so it can be inferred that the gray of his eyes was inherited.[14]:327

Arthur Brisbane, a newspaper editor for the New York World, described Tesla's appearance:
Nikola Tesla is almost the tallest, almost the thinnest and certainly the most serious man who goes to Delmonico's regularly ... He has eyes set very far back in his head. They are rather light. I asked him how he could have such light eyes and be a Slav. He told me that his eyes were once much darker, but that using his mind a great deal had made them many shades lighter. I have often heard it said that using the brain makes the eyes lighter in color. Tesla's confirmation of the theory through his personal experience is important.
He is very thin, is more than six feet tall and weighs less than a hundred and forty pounds. He has very big hands. Many able men do—Lincoln is one instance. His thumbs are remarkably big, even for such big hands. They are extraordinarily big. This is a good sign. The thumb is the intellectual part of the hand. The apes have very small thumbs. Study them and you will notice this.
Nikola Tesla has a head that spreads out at the top like a fan. His head is shaped like a wedge. His chin is as pointed as an ice-pick. His mouth is too small. His chin, though not weak, is not strong enough. His face cannot be studied and judged like the faces of other men, for he is not a worker in practical fields. He lives his life up in the top of his head, where ideas are born, and up there he has plenty of room. His hair is jet black and curly.
He stoops—most men do when they have no peacock blood in them. He lives inside of himself. He takes a profound interest in his own work. He has that supply of self-love and self-confidence which usually goes with success. And he differs from most of the men who are written and talked about in the fact that he has something to tell.[141]

Eidetic memory

Tesla read many works, memorizing complete books, and supposedly possessed a photographic memory.[9]:33 He was a polyglot, speaking eight languages: Serbo-Croatian, Czech, English, French, German, Hungarian, Italian, and Latin.[14]:282 Tesla related in his autobiography that he experienced detailed moments of inspiration. During his early life, Tesla was stricken with illness time and time again. He suffered a peculiar affliction in which blinding flashes of light would appear before his eyes, often accompanied by visions. Often, the visions were linked to a word or idea he might have come across; at other times they would provide the solution to a particular problem he had encountered. Just by hearing the name of an item, he would be able to envision it in realistic detail.
Tesla would visualize an invention in his mind with extreme precision, including all dimensions, before moving to the construction stage, a technique sometimes known as picture thinking. He typically did not make drawings by hand but worked from memory. Beginning in his childhood, Tesla had frequent flashbacks to events that had happened previously in his life.[9]:33

Sleep habits

Tesla claimed to never sleep more than two hours.[14]:46 However, Tesla did admit to "dozing" from time to time "to recharge his batteries."[140]

During his second year of study at Graz, Tesla developed a passion for (and became very proficient at) billiards, chess and card-playing, sometimes spending more than 48 hours in a stretch at a gaming table.[14]:43, 301 On one occasion at his laboratory, Tesla worked for a period of 84 hours without sleep or rest.[14]:208

Kenneth Swezey, a journalist whom Tesla had befriended, confirmed that Tesla rarely slept. Swezey recalled one morning when Tesla called him at 3 a.m.: "I was sleeping in my room like one dead ... Suddenly, the telephone ring awakened me ... [Tesla] spoke animatedly, with pauses, [as he] ... work[ed] out a problem, comparing one theory to another, commenting; and when he felt he had arrived at the solution, he suddenly closed the telephone."[140]

Relationships


Tesla with an unknown woman

Tesla never married, claiming that his chastity was very helpful to his scientific abilities.[9]:33 However, toward the end of his life, he told a reporter, "Sometimes I feel that by not marrying, I made too great a sacrifice to my work ..."[24] There have been numerous accounts of women vying for Tesla's affection, even some madly in love with him.[citation needed] Tesla, though polite and soft-spoken, did not have any known relationships.

Tesla was asocial, and prone to seclude himself with his work.[147][148][1][149] However, when he did engage in a social life, many people spoke very positively and admiringly of Tesla. Robert Underwood Johnson described him as attaining a "distinguished sweetness, sincerity, modesty, refinement, generosity, and force."[24] His loyal secretary, Dorothy Skerrit, wrote: "his genial smile and nobility of bearing always denoted the gentlemanly characteristics that were so ingrained in his soul."[14] Tesla's friend, Julian Hawthorne, wrote, "seldom did one meet a scientist or engineer who was also a poet, a philosopher, an appreciator of fine music, a linguist, and a connoisseur of food and drink."[citation needed]

Mark Twain in Tesla's lab, early 1894

Tesla was a good friend of Robert Underwood Johnson,[150] Francis Marion Crawford, Stanford White,[151] Fritz Lowenstein, George Scherff, Kenneth Swezey.[152][153][154] In middle age, Tesla became a close friend of Mark Twain. They spent a lot of time together in his lab and elsewhere.[150] Twain notably described his induction motor invention as "the most valuable patent since the telephone."[155] In the late 1920s, Tesla befriended George Sylvester Viereck, a poet, writer, mystic, and later, a Nazi propagandist, occasionally attending dinner parties held by Viereck and his wife.[156][157]

Tesla could be harsh at times, openly expressing disgust for overweight people, such as when he fired a secretary because of her weight.[9]:110 He was quick to criticize clothing. On several occasions, Tesla directed a subordinate to go home and change her dress.[9]:33

When Thomas Edison died in 1931, Tesla contributed the only negative opinion to the New York Times, buried in an extensive coverage of Edison's life:
He had no hobby, cared for no sort of amusement of any kind and lived in utter disregard of the most elementary rules of hygiene ... His method was inefficient in the extreme, for an immense ground had to be covered to get anything at all unless blind chance intervened and, at first, I was almost a sorry witness of his doings, knowing that just a little theory and calculation would have saved him 90 percent of the labor. But he had a veritable contempt for book learning and mathematical knowledge, trusting himself entirely to his inventor's instinct and practical American sense.[158]

Views on experimental and theoretical physics


Tesla working in his laboratory.

Tesla exhibited a pre-atomic understanding of physics in his writings;[159] he disagreed with the theory of atoms being composed of smaller subatomic particles, stating there was no such thing as an electron creating an electric charge (he believed that if electrons existed at all they were some fourth state of matter or sub-atom that could only exist in an experimental vacuum and that they had nothing to do with electricity).[14]:249[160] Tesla believed that atoms are immutable—they could not change state or be split in any way. He was a believer in the 19th century concept of an all pervasive "ether" that transmitted electrical energy.[161]

Tesla was generally antagonistic towards theories about the conversion of matter into energy.[14]:247 He was also critical of Einstein's theory of relativity, saying:
I hold that space cannot be curved, for the simple reason that it can have no properties. It might as well be said that God has properties. He has not, but only attributes and these are of our own making. Of properties we can only speak when dealing with matter filling the space. To say that in the presence of large bodies space becomes curved is equivalent to stating that something can act upon nothing. I, for one, refuse to subscribe to such a view.[162]
Tesla claimed to have developed his own physical principle regarding matter and energy that he started working on in 1892[14] and in 1937, at age 81, claimed in a letter to have completed a "dynamic theory of gravity" that "[would] put an end to idle speculations and false conceptions, as that of curved space."[163] He stated that the theory was "worked out in all details" and that he hoped to soon give it to the world.[164] Further elucidation of his theory was never found in his writings.[9]:309

Societal views

Tesla, like many of his era, became a proponent of an imposed selective breeding version of eugenics. His opinion stemmed from the belief that humans' "pity" had interfered with the natural "ruthless workings of nature," rather than from conceptions of a "master race" or inherent superiority of one person over another. His advocacy of it was, however, to push it further. In a 1937 interview, he stated:
... man's new sense of pity began to interfere with the ruthless workings of nature. The only method compatible with our notions of civilization and the race is to prevent the breeding of the unfit by sterilization and the deliberate guidance of the mating instinct ... The trend of opinion among eugenists is that we must make marriage more difficult.
Certainly no one who is not a desirable parent should be permitted to produce progeny. A century from now it will no more occur to a normal person to mate with a person eugenically unfit than to marry a habitual criminal.[165]
In 1926, Tesla commented on the ills of the social subservience of women and the struggle of women toward gender equality, indicated that humanity's future would be run by "Queen Bees." He believed that women would become the dominant sex in the future.[166]

Tesla is widely considered by his biographers as a humanist regarding his worldview.[1]:154[167][168][169][170]

Tesla made predictions about the relevant issues of a post-World War I environment in a printed article, "Science and Discovery are the great Forces which will lead to the Consummation of the War" (20 December 1914).[171] Tesla believed that the League of Nations was not a remedy for the times and issues.[citation needed]

Religious views

Tesla was raised as an Orthodox Christian. Later in his life, he did not consider himself to be a "believer in the orthodox sense," and opposed religious fanaticism.[172] He had a profound respect for both Buddhism and Christianity.[22][172]

In his article, "The Problem of Increasing Human Energy," published in 1900, Tesla stated:
For ages this idea [that each of us is only part of a whole] has been proclaimed in the consummately wise teachings of religion, probably not alone as a means of insuring peace and harmony among men, but as a deeply founded truth. The Buddhist expresses it in one way, the Christian in another, but both say the same: We are all one.[173]
However, his religious views remain uncertain due to other statements that he made.[174][175][176] For example, in his article, "A Machine to End War", published in 1937, Tesla stated:
There is no conflict between the ideal of religion and the ideal of science, but science is opposed to theological dogmas because science is founded on fact. To me, the universe is simply a great machine which never came into being and never will end. The human being is no exception to the natural order. Man, like the universe, is a machine. Nothing enters our minds or determines our actions which is not directly or indirectly a response to stimuli beating upon our sense organs from without. Owing to the similarity of our construction and the sameness of our environment, we respond in like manner to similar stimuli, and from the concordance of our reactions, understanding is born. In the course of ages, mechanisms of infinite complexity are developed, but what we call "soul" or "spirit," is nothing more than the sum of the functionings of the body. When this functioning ceases, the "soul" or the "spirit" ceases likewise.[172]

Literary works

Tesla wrote a number of books and articles for magazines and journals.[177] Among his books are My Inventions: The Autobiography of Nikola Tesla, compiled and edited by Ben Johnston; The Fantastic Inventions of Nikola Tesla, compiled and edited by David Hatcher Childress; and The Tesla Papers.
Many of Tesla's writings are freely available on the web,[178][179][180] including the article "The Problem of Increasing Human Energy," published in The Century Magazine in 1900,[181][182] and the article "Experiments With Alternate Currents Of High Potential And High Frequency," published in his book Inventions, Researches and Writings of Nikola Tesla.[183][184]

Legacy and honors


Tesla on cover of Time Magazine for 20 July 1931.

Nikola Tesla Museum in Belgrade, Serbia.

Nikola Tesla on 100 Serbian dinar banknote.

Tesla's legacy has endured in books, films, radio, TV, music, live theater, comics and video games. The lack of recognition received during his own lifetime has cast him as a tragic and inspirational character, well suited to dramatic fiction. The impact of the technologies invented by Tesla is a recurring theme in several types of science fiction.

Plaques and memorials


Nikola Tesla Corner in New York City
  • The Nikola Tesla Memorial Centre in Smiljan opened in 2006. It features a statue of Tesla designed by sculptor Mile Blažević.[13][194][195]
  • On 7 July 2006, on the corner of Masarykova and Preradovićeva streets in the Lower Town area in Zagreb, the monument of Tesla was unveiled. This monument was designed by Ivan Meštrović in 1952 and was transferred from the Zagreb-based Ruđer Bošković Institute where it had spent previous decades.[196][197]
  • A monument to Tesla was established at Niagara Falls, New York. This monument portraying Tesla reading a set of notes was sculpted by Frano Kršinić. It was presented to the United States by Yugoslavia in 1976 and is an identical copy of the monument standing in front of the University of Belgrade Faculty of Electrical Engineering.
  • A monument of Tesla standing on a portion of an alternator, was established at Queen Victoria Park in Niagara Falls, Ontario, Canada. The monument was officially unveiled on 9 July 2006 on the 150th anniversary of Tesla's birth. The monument was sponsored by St. George Serbian Church, Niagara Falls, and designed by Les Drysdale of Hamilton, Ontario.[198][199] Drysdale's design was the winning design from an international competition.[200]
  • In 2012, Jane Alcorn, president of the nonprofit group The Tesla Science Center at Wardenclyffe, and Matthew Inman, creator of web cartoon The Oatmeal, raised a total of $2,220,511 – $1,370,511 from a campaign and $850,000 from a New York State grant—to buy the property where Wardenclyffe Tower once stood and eventually turn it into a museum.[201][202] The group began negotiations to purchase the Long Island property from Agfa Corporation in October 2012.[203] The purchase was completed in May 2013.[204]
  • A commemorative plaque honoring Nikola Tesla was installed on the façade of the New Yorker Hotel by the IEEE.[205]
  • An intersection named after Tesla, Nikola Tesla Corner, is at the intersection of Sixth Avenue and 40th Street in Manhattan, New York City.
  • A bust and plaque honoring Tesla is outside the Serbian Orthodox Cathedral of Saint Sava (formerly known as Trinity Chapel) at 20 West 26th Street in New York City.[206]

Ice age

Ice age

From Wikipedia, the free encyclopedia

An artist's impression of ice age Earth at glacial maximum. Based on: Crowley, T.J. (1995). "Ice age terrestrial carbon changes revisited". Global Biogeochemical Cycles 9 (3): 377–389. Bibcode:1995GBioC...9..377C. doi:10.1029/95GB01107.
The Antarctic ice sheet. Ice sheets expand during an ice age.
Variations in temperature, CO
2
, and dust from the Vostok ice core over the last 400,000 years

An ice age is a period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Within a long-term ice age, individual pulses of cold climate are termed "glacial periods" (or alternatively "glacials" or "glaciations" or colloquially as "ice age"), and intermittent warm periods are called "interglacials". Glaciologically, ice age implies the presence of extensive ice sheets in the northern and southern hemispheres.[1] By this definition, we are in an interglacial period - the holocene, of the ice age that began 2.6 million years ago at the start of the Pleistocene epoch, because the Greenland, Arctic, and Antarctic ice sheets still exist.[2]

Origin of ice age theory

In 1742 Pierre Martel (1706–1767), an engineer and geographer living in Geneva, visited the valley of Chamonix in the Alps of Savoy.[3][4] Two years later he published an account of his journey. He reported that the inhabitants of that valley attributed the dispersal of erratic boulders to the fact that the glaciers had once extended much farther.[5][6] Later similar explanations were reported from other regions of the Alps. In 1815 the carpenter and chamois hunter Jean-Pierre Perraudin (1767–1858) explained erratic boulders in the Val de Bagnes in the Swiss canton of Valais as being due to glaciers previously extending further.[7] An unknown woodcutter from Meiringen in the Bernese Oberland advocated a similar idea in a discussion with the Swiss-German geologist Jean de Charpentier (1786–1855) in 1834.[8] Comparable explanations are also known from the Val de Ferret in the Valais and the Seeland in western Switzerland[9] and in Goethe's Scientific Work.[10] Such explanations could also be found in other parts of the world. When the Bavarian naturalist Ernst von Bibra (1806–1878) visited the Chilean Andes in 1849–1850 the natives attributed fossil moraines to the former action of glaciers.[11]

Meanwhile, European scholars had begun to wonder what had caused the dispersal of erratic material. From the middle of the 18th century some discussed ice as a means of transport. The Swedish mining expert Daniel Tilas (1712–1772) was, in 1742, the first person to suggest drifting sea ice in order to explain the presence of erratic boulders in the Scandinavian and Baltic regions.[12] In 1795, the Scottish philosopher and gentleman naturalist, James Hutton (1726–1797), explained erratic boulders in the Alps with the action of glaciers.[13] Two decades later, in 1818, the Swedish botanist Göran Wahlenberg (1780–1851) published his theory of a glaciation of the Scandinavian peninsula. He regarded glaciation as a regional phenomenon.[14] Only a few years later, the Danish-Norwegian Geologist Jens Esmark (1763–1839) argued a sequence of worldwide ice ages. In a paper published in 1824, Esmark proposed changes in climate as the cause of those glaciations. He attempted to show that they originated from changes in the Earth's orbit.[15] During the following years, Esmark’s ideas were discussed and taken over in parts by Swedish, Scottish and German scientists. At the University of Edinburgh Robert Jameson (1774–1854) seemed to be relatively open towards Esmark's ideas, as reviewed by Norwegian professor of glaciology Bjørn G. Andersen (1992).[16] Jameson's remarks about ancient glaciers in Scotland were most probably prompted by Esmark.[17] In Germany, Albrecht Reinhard Bernhardi (1797–1849), professor of forestry at Dreissigacker, adopted Esmark's theory. In a paper published in 1832, Bernhardi speculated about former polar ice caps reaching as far as the temperate zones of the globe.[18]

Independently of these debates, the Swiss civil engineer Ignaz Venetz (1788–1859) in 1829, explained the dispersal of erratic boulders in the Alps, the nearby Jura Mountains and the North German Plain as being due to huge glaciers. When he read his paper before the Schweizerische Naturforschende Gesellschaft, most scientists remained sceptical.[19] Finally, Venetz managed to convince his friend Jean de Charpentier. De Charpentier transformed Venetz's idea into a theory with a glaciation limited to the Alps. His thoughts resembled Wahlenberg's theory. In fact, both men shared the same volcanistic, or in de Charpentier’s case rather plutonistic assumptions, about earth history. In 1834, de Charpentier presented his paper before the Schweizerische Naturforschende Gesellschaft.[20] In the meantime, the German botanist Karl Friedrich Schimper (1803–1867) was studying mosses which were growing on erratic boulders in the alpine upland of Bavaria. He began to wonder where such masses of stone had come from. During the summer of 1835 he made some excursions to the Bavarian Alps. Schimper came to the conclusion that ice must have been the means of transport for the boulders in the alpine upland. In the winter of 1835 to 1836 he held some lectures in Munich. Schimper then assumed that there must have been global times of obliteration ("Verödungszeiten") with a cold climate and frozen water.[21] Schimper spent the summer months of 1836 at Devens, near Bex, in the Swiss Alps with his former university friend Louis Agassiz (1801–1873) and Jean de Charpentier. Schimper, de Charpentier and possibly Venetz convinced Agassiz that there had been a time of glaciation. During Winter 1836/7 Agassiz and Schimper developed the theory of a sequence of glaciations. They mainly drew upon the preceding works of Goethe,[22] of Venetz, of de Charpentier and on their own fieldwork. There are indications that Agassiz was already familiar with Bernhardi's paper at that time.[23] At the beginning of 1837 Schimper coined the term ice age ("Eiszeit").[24] In July 1837 Agassiz presented their synthesis before the annual meeting of the Schweizerische Naturforschende Gesellschaft at Neuchâtel. The audience was very critical or even opposed the new theory because it contradicted the established opinions on climatic history. Most contemporary scientists thought that the earth had been gradually cooling down since its birth as a molten globe.[25]

In order to overcome this rejection, Agassiz embarked on geological fieldwork. He published his book Study on glaciers ("Études sur les glaciers") in 1840.[26] De Charpentier was put out by this as he had also been preparing a book about the glaciation of the Alps. De Charpentier felt that Agassiz should have given him precedence as it was he who had introduced Agassiz to in-depth glacial research.[27] Besides that, Agassiz had, as a result of personal quarrels, omitted any mention of Schimper in his book.[28]

All together, it took several decades until the ice age theory was fully accepted. This happened on an international scale in the second half of the 1870s following the work of James Croll including the publication of Climate and Time, in Their Geological Relations in 1875 which provided a credible explanation for the causes of ice ages.[29]

Evidence for ice ages

There are three main types of evidence for ice ages: geological, chemical, and paleontological.
Geological evidence for ice ages comes in various forms, including rock scouring and scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites and glacial erratics. Successive glaciations tend to distort and erase the geological evidence, making it difficult to interpret. Furthermore, this evidence was difficult to date exactly; early theories assumed that the glacials were short compared to the long interglacials. The advent of sediment and ice cores revealed the true situation: glacials are long, interglacials short. It took some time for the current theory to be worked out.

The chemical evidence mainly consists of variations in the ratios of isotopes in fossils present in sediments and sedimentary rocks and ocean sediment cores. For the most recent glacial periods ice cores provide climate proxies from their ice, and atmospheric samples from included bubbles of air. Because water containing heavier isotopes has a higher heat of evaporation, its proportion decreases with colder conditions.[30] This allows a temperature record to be constructed. However, this evidence can be confounded by other factors recorded by isotope ratios.

The paleontological evidence consists of changes in the geographical distribution of fossils. During a glacial period cold-adapted organisms spread into lower latitudes, and organisms that prefer warmer conditions become extinct or are squeezed into lower latitudes. This evidence is also difficult to interpret because it requires (1) sequences of sediments covering a long period of time, over a wide range of latitudes and which are easily correlated; (2) ancient organisms which survive for several million years without change and whose temperature preferences are easily diagnosed; and (3) the finding of the relevant fossils.

Despite the difficulties, analysis of ice core and ocean sediment cores[31] has shown periods of glacials and interglacials over the past few million years. These also confirm the linkage between ice ages and continental crust phenomena such as glacial moraines, drumlins, and glacial erratics. Hence the continental crust phenomena are accepted as good evidence of earlier ice ages when they are found in layers created much earlier than the time range for which ice cores and ocean sediment cores are available.

Major ice ages

Ice age map of northern Germany and its northern neighbours. Red: maximum limit of Weichselian glacial; yellow: Saale glacial at maximum (Drenthe stage); blue: Elster glacial maximum glaciation.
Timeline of glaciations, shown in blue.

There have been at least five major ice ages in the Earth's past (the Huronian, Cryogenian, Andean-Saharan, Karoo Ice Age and the Quaternary glaciation). Outside these ages, the Earth seems to have been ice-free even in high latitudes.[32][33]

Rocks from the earliest well established ice age, called the Huronian, formed around 2.4 to 2.1 Ga (billion years) ago during the early Proterozoic Eon. Several hundreds of km of the Huronian Supergroup are exposed 10–100 km north of the north shore of Lake Huron extending from near Sault Ste. Marie to Sudbury, northeast of Lake Huron, with giant layers of now-lithified till beds, dropstones, varves, outwash, and scoured basement rocks. Correlative Huronian deposits have been found near Marquette, Michigan, and correlation has been made with Paleoproterozoic glacial deposits from Western Australia.

The next well-documented ice age, and probably the most severe of the last billion years, occurred from 850 to 630 million years ago (the Cryogenian period) and may have produced a Snowball Earth in which glacial ice sheets reached the equator,[34] possibly being ended by the accumulation of greenhouse gases such as CO
2
produced by volcanoes. "The presence of ice on the continents and pack ice on the oceans would inhibit both silicate weathering and photosynthesis, which are the two major sinks for CO
2
at present."[35] It has been suggested that the end of this ice age was responsible for the subsequent Ediacaran and Cambrian Explosion, though this model is recent and controversial.
The Andean-Saharan occurred from 460 to 420 million years ago, during the Late Ordovician and the Silurian period.

The evolution of land plants at the onset of the Devonian period caused a long term increase in planetary oxygen levels and reduction of CO
2
levels, which resulted in the Karoo Ice Age. It is named after the glacial tills found in the Karoo region of South Africa, where evidence for this ice age was first clearly identified. There were extensive polar ice caps at intervals from 360 to 260 million years ago in South Africa during the Carboniferous and early Permian Periods. Correlatives are known from Argentina, also in the center of the ancient supercontinent Gondwanaland.
Sediment records showing the fluctuating sequences of glacials and interglacials during the last several million years.

The current ice age, the Pliocene-Quaternary glaciation, started about 2.58 million years ago during the late Pliocene, when the spread of ice sheets in the Northern Hemisphere began. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000- and 100,000-year time scales called glacial periods, glacials or glacial advances, and interglacial periods, interglacials or glacial retreats. The earth is currently in an interglacial, and the last glacial period ended about 10,000 years ago. All that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and smaller glaciers such as on Baffin Island.

Ice ages can be further divided by location and time; for example, the names Riss (180,000–130,000 years bp) and Würm (70,000–10,000 years bp) refer specifically to glaciation in the Alpine region. The maximum extent of the ice is not maintained for the full interval. The scouring action of each glaciation tends to remove most of the evidence of prior ice sheets almost completely, except in regions where the later sheet does not achieve full coverage.

Glacials and interglacials

Shows the pattern of temperature and ice volume changes associated with recent glacials and interglacials
Minimum (interglacial, black) and maximum (glacial, grey) glaciation of the northern hemisphere
Minimum (interglacial, black) and maximum (glacial, grey) glaciation of the southern hemisphere

Within the ice ages (or at least within the current one), more temperate and more severe periods occur. The colder periods are called glacial periods, the warmer periods interglacials, such as the Eemian Stage.

Glacials are characterized by cooler and drier climates over most of the Earth and large land and sea ice masses extending outward from the poles. Mountain glaciers in otherwise unglaciated areas extend to lower elevations due to a lower snow line. Sea levels drop due to the removal of large volumes of water above sea level in the icecaps. There is evidence that ocean circulation patterns are disrupted by glaciations. Since the Earth has significant continental glaciation in the Arctic and Antarctic, we are currently in a glacial minimum of a glaciation. Such a period between glacial maxima is known as an interglacial. The glacials and interglacials also coincided with changes in the Earth’s orbit called Milankovitch cycles.

The Earth has been in an interglacial period known as the Holocene for more than 11,000 years. It was conventional wisdom that the typical interglacial period lasts about 12,000 years, but this has been called into question recently. For example, an article in Nature[36] argues that the current interglacial might be most analogous to a previous interglacial that lasted 28,000 years. Predicted changes in orbital forcing suggest that the next glacial period would begin at least 50,000 years from now, even in absence of human-made global warming[37] (see Milankovitch cycles). Moreover, anthropogenic forcing from increased greenhouse gases might outweigh orbital forcing for as long as intensive use of fossil fuels continues.[38]

Positive and negative feedbacks in glacial periods

Each glacial period is subject to positive feedback which makes it more severe and negative feedback which mitigates and (in all cases so far) eventually ends it.

Positive feedback processes

Ice and snow increase the Earth's albedo, i.e. they make it reflect more of the sun's energy and absorb less. Hence, when the air temperature decreases, ice and snow fields grow, and this continues until competition with a negative feedback mechanism forces the system to an equilibrium. Also, the reduction in forests caused by the ice's expansion increases albedo.

Another theory proposed by Ewing and Donn in 1956[39] hypothesized that an ice-free Arctic Ocean leads to increased snowfall at high latitudes. When low-temperature ice covers the Arctic Ocean there is little evaporation or sublimation and the polar regions are quite dry in terms of precipitation, comparable to the amount found in mid-latitude deserts. This low precipitation allows high-latitude snowfalls to melt during the summer. An ice-free Arctic Ocean absorbs solar radiation during the long summer days, and evaporates more water into the Arctic atmosphere. With higher precipitation, portions of this snow may not melt during the summer and so glacial ice can form at lower altitudes and more southerly latitudes, reducing the temperatures over land by increased albedo as noted above. Furthermore, under this hypothesis the lack of oceanic pack ice allows increased exchange of waters between the Arctic and the North Atlantic Oceans, warming the Arctic and cooling the North Atlantic. (Current projected consequences of global warming include a largely ice-free Arctic Ocean within 5–20 years, see Arctic shrinkage.) Additional fresh water flowing into the North Atlantic during a warming cycle may also reduce the global ocean water circulation (see Shutdown of thermohaline circulation). Such a reduction (by reducing the effects of the Gulf Stream) would have a cooling effect on northern Europe, which in turn would lead to increased low-latitude snow retention during the summer. It has also been suggested that during an extensive glacial, glaciers may move through the Gulf of Saint Lawrence, extending into the North Atlantic ocean far enough to block the Gulf Stream.

Negative feedback processes

Ice sheets that form during glaciations cause erosion of the land beneath them. After some time, this will reduce land above sea level and thus diminish the amount of space on which ice sheets can form. This mitigates the albedo feedback, as does the lowering in sea level that accompanies the formation of ice sheets[citation needed].

Another factor is the increased aridity occurring with glacial maxima, which reduces the precipitation available to maintain glaciation. The glacial retreat induced by this or any other process can be amplified by similar inverse positive feedbacks as for glacial advances.[citation needed]

According to research published in Nature Geoscience, human emissions of carbon dioxide will defer the next ice age. Researchers used data on the Earth's orbit to find the historical warm interglacial period that looks most like the current one and from this have predicted that the next ice age would usually begin within 1,500 years. They go on to say that emissions have been so high that it will not.[40]

Causes of ice ages

The causes of ice ages are not fully understood for either the large-scale ice age periods or the smaller ebb and flow of glacial–interglacial periods within an ice age. The consensus is that several factors are important: atmospheric composition, such as the concentrations of carbon dioxide and methane (the specific levels of the previously mentioned gases are now able to be seen with the new ice core samples from EPICA Dome C in Antarctica over the past 800,000 years[41] ); changes in the Earth's orbit around the Sun known as Milankovitch cycles; the motion of tectonic plates resulting in changes in the relative location and amount of continental and oceanic crust on the Earth's surface, which affect wind and ocean currents; variations in solar output; the orbital dynamics of the Earth-Moon system; and the impact of relatively large meteorites, and volcanism including eruptions of supervolcanoes.[citation needed]

Some of these factors influence each other. For example, changes in Earth's atmospheric composition (especially the concentrations of greenhouse gases) may alter the climate, while climate change itself can change the atmospheric composition (for example by changing the rate at which weathering removes CO
2
).

Maureen Raymo, William Ruddiman and others propose that the Tibetan and Colorado Plateaus are immense CO
2
"scrubbers" with a capacity to remove enough CO
2
from the global atmosphere to be a significant causal factor of the 40 million year Cenozoic Cooling trend. They further claim that approximately half of their uplift (and CO
2
"scrubbing" capacity) occurred in the past 10 million years.[42][43]

Changes in Earth's atmosphere

There is considerable evidence that over the very recent period of the last 100–1000 years, the sharp increases in human activity, especially the burning of fossil fuels, has caused the parallel sharp and accelerating increase in atmospheric greenhouse gases which trap the sun's heat. The consensus theory of the scientific community is that the resulting greenhouse effect is a principal cause of the increase in global warming which has occurred over the same period, and a chief contributor to the accelerated melting of the remaining glaciers and polar ice. A 2012 investigation finds that dinosaurs released methane through digestion in a similar amount to humanity's current methane release, which "could have been a key factor" to the very warm climate 150 million years ago.[44]

There is evidence that greenhouse gas levels fell at the start of ice ages and rose during the retreat of the ice sheets, but it is difficult to establish cause and effect (see the notes above on the role of weathering). Greenhouse gas levels may also have been affected by other factors which have been proposed as causes of ice ages, such as the movement of continents and volcanism.

The Snowball Earth hypothesis maintains that the severe freezing in the late Proterozoic was ended by an increase in CO
2
levels in the atmosphere, and some supporters of Snowball Earth argue that it was caused by a reduction in atmospheric CO
2
. The hypothesis also warns of future Snowball Earths.

In 2009, further evidence was provided that changes in solar insolation provide the initial trigger for the Earth to warm after an Ice Age, with secondary factors like increases in greenhouse gases accounting for the magnitude of the change.[45]

William Ruddiman has proposed the early anthropocene hypothesis, according to which the anthropocene era, as some people call the most recent period in the Earth's history when the activities of the human species first began to have a significant global impact on the Earth's climate and ecosystems, did not begin in the 18th century with the advent of the Industrial Era, but dates back to 8,000 years ago, due to intense farming activities of our early agrarian ancestors. It was at that time that atmospheric greenhouse gas concentrations stopped following the periodic pattern of the Milankovitch cycles. In his overdue-glaciation hypothesis Ruddiman states that an incipient glacial would probably have begun several thousand years ago, but the arrival of that scheduled glacial was forestalled by the activities of early farmers.[46]

At a meeting of the American Geophysical Union (December 17, 2008), scientists detailed evidence in support of the controversial idea that the introduction of large-scale rice agriculture in Asia, coupled with extensive deforestation in Europe began to alter world climate by pumping significant amounts of greenhouse gases into the atmosphere over the last 1,000 years. In turn, a warmer atmosphere heated the oceans making them much less efficient storehouses of carbon dioxide and reinforcing global warming, possibly forestalling the onset of a new glacial age.[47]

Position of the continents

The geological record appears to show that ice ages start when the continents are in positions which block or reduce the flow of warm water from the equator to the poles and thus allow ice sheets to form. The ice sheets increase the Earth's reflectivity and thus reduce the absorption of solar radiation. With less radiation absorbed the atmosphere cools; the cooling allows the ice sheets to grow, which further increases reflectivity in a positive feedback loop. The ice age continues until the reduction in weathering causes an increase in the greenhouse effect.

There are three known configurations of the continents which block or reduce the flow of warm water from the equator to the poles:[citation needed]
  • A continent sits on top of a pole, as Antarctica does today.
  • A polar sea is almost land-locked, as the Arctic Ocean is today.
  • A supercontinent covers most of the equator, as Rodinia did during the Cryogenian period.
Since today's Earth has a continent over the South Pole and an almost land-locked ocean over the North Pole, geologists believe that Earth will continue to experience glacial periods in the geologically near future.

Some scientists believe that the Himalayas are a major factor in the current ice age, because these mountains have increased Earth's total rainfall and therefore the rate at which CO
2
is washed out of the atmosphere, decreasing the greenhouse effect.[43] The Himalayas' formation started about 70 million years ago when the Indo-Australian Plate collided with the Eurasian Plate, and the Himalayas are still rising by about 5 mm per year because the Indo-Australian plate is still moving at 67 mm/year. The history of the Himalayas broadly fits the long-term decrease in Earth's average temperature since the mid-Eocene, 40 million years ago.

Fluctuations in ocean currents

Another important contribution to ancient climate regimes is the variation of ocean currents, which are modified by continent position, sea levels and salinity, as well as other factors. They have the ability to cool (e.g. aiding the creation of Antarctic ice) and the ability to warm (e.g. giving the British Isles a temperate as opposed to a boreal climate). The closing of the Isthmus of Panama about 3 million years ago may have ushered in the present period of strong glaciation over North America by ending the exchange of water between the tropical Atlantic and Pacific Oceans.[48]

Analyses suggest that ocean current fluctuations can adequately account for recent glacial oscillations. During the last glacial period the sea-level has fluctuated 20–30 m as water was sequestered, primarily in the northern hemisphere ice sheets. When ice collected and the sea level dropped sufficiently, flow through the Bering Strait (the narrow strait between Siberia and Alaska is ~50 m deep today) was reduced, resulting in increased flow from the North Atlantic. This realigned the thermohaline circulation in the Atlantic, increasing heat transport into the Arctic, which melted the polar ice accumulation and reduced other continental ice sheets. The release of water raised sea levels again, restoring the ingress of colder water from the Pacific with an accompanying shift to northern hemisphere ice accumulation.[49]

Uplift of the Tibetan plateau and surrounding mountain areas above the snowline

Matthias Kuhle's geological theory of Ice Age development was suggested by the existence of an ice sheet covering the Tibetan plateau during the Ice Ages (Last Glacial Maximum?). According to Kuhle, the plate-tectonic uplift of Tibet past the snow-line has led to a surface of c. 2,400,000 square kilometres (930,000 sq mi) changing from bare land to ice with a 70% greater albedo. The reflection of energy into space resulted in a global cooling, triggering the Pleistocene Ice Age. Because this highland is at a subtropical latitude, with 4 to 5 times the insolation of high-latitude areas, what would be Earth's strongest heating surface has turned into a cooling surface.

Kuhle explains the interglacial periods by the 100,000-year cycle of radiation changes due to variations of the Earth's orbit. This comparatively insignificant warming, when combined with the lowering of the Nordic inland ice areas and Tibet due to the weight of the superimposed ice-load, has led to the repeated complete thawing of the inland ice areas.[50][51][52][53]

Variations in Earth's orbit (Milankovitch cycles)

The Milankovitch cycles are a set of cyclic variations in characteristics of the Earth's orbit around the Sun. Each cycle has a different length, so at some times their effects reinforce each other and at other times they (partially) cancel each other.
Past and future of daily average insolation at top of the atmosphere on the day of the summer solstice, at 65 N latitude.

There is strong evidence that the Milankovitch cycles affect the occurrence of glacial and interglacial periods within an ice age. The present ice age is the most studied and best understood, particularly the last 400,000 years, since this is the period covered by ice cores that record atmospheric composition and proxies for temperature and ice volume. Within this period, the match of glacial/interglacial frequencies to the Milanković orbital forcing periods is so close that orbital forcing is generally accepted. The combined effects of the changing distance to the Sun, the precession of the Earth's axis, and the changing tilt of the Earth's axis redistribute the sunlight received by the Earth. Of particular importance are changes in the tilt of the Earth's axis, which affect the intensity of seasons. For example, the amount of solar influx in July at 65 degrees north latitude varies by as much as 22% (from 450 W/m² to 550 W/m²). It is widely believed that ice sheets advance when summers become too cool to melt all of the accumulated snowfall from the previous winter. Some workers believe that the strength of the orbital forcing is too small to trigger glaciations, but feedback mechanisms like CO
2
may explain this mismatch.

While Milankovitch forcing predicts that cyclic changes in the Earth's orbital elements can be expressed in the glaciation record, additional explanations are necessary to explain which cycles are observed to be most important in the timing of glacial–interglacial periods. In particular, during the last 800,000 years, the dominant period of glacial–interglacial oscillation has been 100,000 years, which corresponds to changes in Earth's orbital eccentricity and orbital inclination. Yet this is by far the weakest of the three frequencies predicted by Milankovitch. During the period 3.0–0.8 million years ago, the dominant pattern of glaciation corresponded to the 41,000-year period of changes in Earth's obliquity (tilt of the axis). The reasons for dominance of one frequency versus another are poorly understood and an active area of current research, but the answer probably relates to some form of resonance in the Earth's climate system.

The "traditional" Milankovitch explanation struggles to explain the dominance of the 100,000-year cycle over the last 8 cycles. Richard A. Muller, Gordon J. F. MacDonald,[54][55][56] and others have pointed out that those calculations are for a two-dimensional orbit of Earth but the three-dimensional orbit also has a 100,000-year cycle of orbital inclination. They proposed that these variations in orbital inclination lead to variations in insolation, as the Earth moves in and out of known dust bands in the solar system. Although this is a different mechanism to the traditional view, the "predicted" periods over the last 400,000 years are nearly the same. The Muller and MacDonald theory, in turn, has been challenged by Jose Antonio Rial.[57]

Another worker, William Ruddiman, has suggested a model that explains the 100,000-year cycle by the modulating effect of eccentricity (weak 100,000-year cycle) on precession (26,000-year cycle) combined with greenhouse gas feedbacks in the 41,000- and 26,000-year cycles. Yet another theory has been advanced by Peter Huybers who argued that the 41,000-year cycle has always been dominant, but that the Earth has entered a mode of climate behavior where only the second or third cycle triggers an ice age. This would imply that the 100,000-year periodicity is really an illusion created by averaging together cycles lasting 80,000 and 120,000 years.[58] This theory is consistent with a simple empirical multi-state model proposed by Didier Paillard.[59] Paillard suggests that the late Pleistocene glacial cycles can be seen as jumps between three quasi-stable climate states. The jumps are induced by the orbital forcing, while in the early Pleistocene the 41,000-year glacial cycles resulted from jumps between only two climate states. A dynamical model explaining this behavior was proposed by Peter Ditlevsen.[60] This is in support of the suggestion that the late Pleistocene glacial cycles are not due to the weak 100,000-year eccentricity cycle, but a non-linear response to mainly the 41,000-year obliquity cycle.

Variations in the Sun's energy output 

There are at least two types of variation in the Sun's energy output
  • In the very long term, astrophysicists believe that the Sun's output increases by about 7% every one billion (109) years.
  • Shorter-term variations such as sunspot cycles, and longer episodes such as the Maunder minimum, which occurred during the coldest part of the Little Ice Age.
The long-term increase in the Sun's output cannot be a cause of ice ages.

Volcanism

Volcanic eruptions may have contributed to the inception and/or the end of ice age periods. At times during the paleoclimate, carbon dioxide levels were two or three times greater than today. Volcanoes and movements in continental plates contributed to high amounts of CO2 in the atmosphere. Carbon dioxide from volcanoes probably contributed to periods with highest overall temperatures.[61] One suggested explanation of the Paleocene-Eocene Thermal Maximum is that undersea volcanoes released methane from clathrates and thus caused a large and rapid increase in the greenhouse effect.[citation needed] There appears to be no geological evidence for such eruptions at the right time, but this does not prove they did not happen.

Recent glacial and interglacial phases

Northern hemisphere glaciation during the last ice ages. The set up of 3 to 4 km thick ice sheets caused a sea level lowering of about 120 m.

Glacial stages in North America

The major glacial stages of the current ice age in North America are the Illinoian, Sangamonian and Wisconsin stages. The use of the Nebraskan, Afton, Kansan, and Yarmouthian (Yarmouth) stages to subdivide the ice age in North America have been discontinued by Quaternary geologists and geomorphologists. These stages have all been merged into the Pre-Illinoian Stage in the 1980s.[62][63][64]

During the most recent North American glaciation, during the latter part of the Wisconsin Stage (26,000 to 13,300 years ago), ice sheets extended to about 45 degrees north latitude. These sheets were 3 to 4 km thick.[63]

This Wisconsin glaciation left widespread impacts on the North American landscape. The Great Lakes and the Finger Lakes were carved by ice deepening old valleys. Most of the lakes in Minnesota and Wisconsin were gouged out by glaciers and later filled with glacial meltwaters. The old Teays River drainage system was radically altered and largely reshaped into the Ohio River drainage system. Other rivers were dammed and diverted to new channels, such as the Niagara, which formed a dramatic waterfall and gorge, when the waterflow encountered a limestone escarpment. Another similar waterfall, at the present Clark Reservation State Park near Syracuse, New York, is now dry.

The area from Long Island to Nantucket was formed from glacial till, and the plethora of lakes on the Canadian Shield in northern Canada can be almost entirely attributed to the action of the ice. As the ice retreated and the rock dust dried, winds carried the material hundreds of miles, forming beds of loess many dozens of feet thick in the Missouri Valley. Isostatic rebound continues to reshape the Great Lakes and other areas formerly under the weight of the ice sheets.

The Driftless Zone, a portion of western and southwestern Wisconsin along with parts of adjacent Minnesota, Iowa, and Illinois, was not covered by glaciers.

Last Glacial Period in the semiarid Andes around Aconcagua and Tupungato

A specially interesting climatic change during glacial times has taken place in the semi-arid Andes.
Beside the expected cooling down in comparison with the current climate, a significant precipitation is concerned here. So, researches in the presently semiarid subtropic Aconcagua-massif (6,962 m) have shown an unexpectedly extensive glacial glaciation of the type "ice stream network".[65][66][67][68][69] The connected valley glaciers exceeding 100 km in length, flowed down on the East-side of this section of the Andes at 32–34°S and 69–71°W as far as a height of 2,060 m and on the western luff-side still clearly deeper.[69][70] Where current glaciers scarcely reach 10 km in length, the snowline (ELA) runs at a height of 4,600 m and at that time was lowered to 3,200 m asl, i.e. about 1,400 m. From this follows that—beside of an annual depression of temperature about c. 8.4°C— here was an increase in precipitation. Accordingly, at glacial times the humid climatic belt that today is situated several latitude degrees further to the S, was shifted much further to the N.[68][69]

Effects of glaciation

Scandinavia exhibits some of the typical effects of ice age glaciation such as fjords and lakes.

Although the last glacial period ended more than 8,000 years ago, its effects can still be felt today.
For example, the moving ice carved out the landscape in Canada (See Canadian Arctic Archipelago), Greenland, northern Eurasia and Antarctica. The erratic boulders, till, drumlins, eskers, fjords, kettle lakes, moraines, cirques, horns, etc., are typical features left behind by the glaciers.
The weight of the ice sheets was so great that they deformed the Earth's crust and mantle. After the ice sheets melted, the ice-covered land rebounded. Due to the high viscosity of the Earth's mantle, the flow of mantle rocks which controls the rebound process is very slow—at a rate of about 1 cm/year near the center of rebound area today.

During glaciation, water was taken from the oceans to form the ice at high latitudes, thus global sea level dropped by about 110 meters, exposing the continental shelves and forming land-bridges between land-masses for animals to migrate. During deglaciation, the melted ice-water returned to the oceans, causing sea level to rise. This process can cause sudden shifts in coastlines and hydration systems resulting in newly submerged lands, emerging lands, collapsed ice dams resulting in salination of lakes, new ice dams creating vast areas of freshwater, and a general alteration in regional weather patterns on a large but temporary scale. It can even cause temporary reglaciation. This type of chaotic pattern of rapidly changing land, ice, saltwater and freshwater has been proposed as the likely model for the Baltic and Scandinavian regions, as well as much of central North America at the end of the last glacial maximum, with the present-day coastlines only being achieved in the last few millennia of prehistory. Also, the effect of elevation on Scandinavia submerged a vast continental plain that had existed under much of what is now the North Sea, connecting the British Isles to Continental Europe.[71]

The redistribution of ice-water on the surface of the Earth and the flow of mantle rocks causes changes in the gravitational field as well as changes to the distribution of the moment of inertia of the Earth. These changes to the moment of inertia result in a change in the angular velocity, axis, and wobble of the Earth's rotation.

The weight of the redistributed surface mass loaded the lithosphere, caused it to flexure and also induced stress within the Earth. The presence of the glaciers generally suppressed the movement of faults below.[72][73][74] However, during deglaciation, the faults experience accelerated slip triggering earthquakes. Earthquakes triggered near the ice margin may in turn accelerate ice calving and may account for the Heinrich events.[75] As more ice is removed near the ice margin, more intraplate earthquakes are induced and this positive feedback may explain the fast collapse of ice sheets.
In Europe, glacial erosion and isostatic sinking from weight of ice made the Baltic Sea, which before the Ice Age was all land drained by the Eridanos River.

Representation of a Lie group

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