हेनरी कैवेंडिश

प्रारंभिक जीवन

हेनरी कैवेंडिश का जन्म नीस में 10 अक्टूबर 1731 को हुआ था, जहां उस समय उनका परिवार रहता था। उनकी मां लेडी ऐनी ग्रे, हेनरी ग्रे (केंट के पहले ड्यूक) की चौथी बेटी थी, और उनके पिता लार्ड चार्ल्स कैवेंडिश, विलियम कैवेंडिश (देवांशिरे के दूसरे ड्यूक) के तीसरे बेटे थे। उनके वंश का निशान आठ सदियों बाद नॉर्मन के समय में मिला और बारीकी से यह ग्रेट ब्रिटेन के कई कुलीन परिवारों से जुड़ा था। उनकी मां की, अपने दूसरे बेटे, फ्रेडरिक के जन्म के तीन महीने बाद और हेनरी के दूसरे जन्मदिन से पहले थोड़े समय पहले, 1733 में मृत्यु हो गयी। 11 साल की उम्र में, हेनरी ने लंदन के पास एक निजी स्कूल, हैकनी अकादमी में भाग लिया। 18 साल (24 नवंबर 1748 में)  की उम्र में वह, सेंट पीटर कॉलेज में कैम्ब्रिज विश्वविद्यालय में प्रवेश लिया, अब पेतेर्होउस के नाम से जाना जाता है, लेकिन तीन साल बाद 23 फ़रवरी 1751 एक डिग्री लेने बिना (जोकि एक आम बात थी) ही छोड़ दिया। इसके बाद वह लंदन में अपने पिता के साथ रहते थे, जहां उन्होंने जल्द ही अपना प्रयोगशाला बना लिया था।
लार्ड चार्ल्स कैवेंडिश सेवा का जीवन जीते थे, पहले राजनीति में और फिर तेजी से विज्ञान के क्षेत्र में, विशेष रूप से लंदन की रॉयल सोसायटी में। 1758 में वह रॉयल सोसाइटी की बैठकों के लिए हेनरी को ले गए और रॉयल सोसाइटी क्लब के रात्रिभोज के लिए भी ले गये। 1760 में हेनरी कैवेंडिश इन दोनों समूहों के लिए चुने गये, और फिर उनकी उपस्थिति में तत्पर रहे। वास्तव में उन्होंने राजनीती में कोई हिस्सा नहीं लिया था, लेकिन, अपने पिता के समान, वह विज्ञान के लिए सेवा का जीवन जीते थे, अपने दोनों शोध के माध्यम से और वैज्ञानिक संगठनों में अपनी भागीदारी के माध्यम से। वह लंदन की रॉयल सोसायटी की परिषद में सक्रिय थे (जोकि 1765 में चुनी गयी थी)। वैज्ञानिक उपकरणों के इस्तेमाल में उनकी रुचि और विशेषज्ञता रॉयल सोसाइटी के मौसमविज्ञान-संबंधी उपकरणों की समीक्षा के एक समिति का मुखिया बनने के लिए दबाव डाला और रॉयल ग्रीनविच वेधशाला के उपकरणों का आकलन करने में मदद किया। उनका पहला पत्र, "कृत्रिम अकड़", 1766 में निर्गत हुआ। जिस पर अन्य समितियों के कागजात की समिति शामिल थे उसपर उन्होंने कार्य किया, जो दार्शनिक ट्रांजेक्शन में प्रकाशन के लिए पत्रों का चुनाव हुआ, और शुक्र (1769) के पारगमन के लिए समितियां, पहाड़ों के गुरुत्वाकर्षण के आकर्षण (1774) के लिए, और उत्तरी ध्रुव की खोज में कोंसटेंटाइन फिप्स के अभियान (1773) के लिए वैज्ञानिक निर्देश के लिए और नॉर्थवेस्ट पारित के लिए। 1773 में हेनरी ब्रिटिश संग्रहालय के एक निर्वाचित ट्रस्टी के रूप में अपने पिता शामिल हो गए, जो करने के लिए वह समय और प्रयास की एक अच्छा सौदा समर्पित कर दिया। जल्द ही ग्रेट ब्रिटेन के रॉयल इंस्टीट्यूशन के बाद स्थापित किया गया, कैवेंडिश (1800 में) एक प्रबंधक बन गया और एक सक्रिय रुचि ली, विशेष रूप से प्रयोगशाला में, जहां उन्होंने ओब्सेर्व किया और हम्फ्री डेवी के रासायनिक प्रयोगों में मदद की।

रसायन विज्ञान अनुसंधान

लगभग उनके पिता की मृत्यु के समय, कैवेंडिश चार्ल्स ब्लाग्डेन के साथ मिलकर काम करना शुरू किया, एक संघ जिसने ब्लाग्डेन को लंदन के वैज्ञानिक समाज में पूरी तरह से प्रवेश करने में मदद किया। बदले में, ब्लाग्डेन ने कैवेंडिश से थोड़ी दूरी पर दुनिया बनाये रखने में मदद की। अब तक कैवेंडिश ने किताबे और कुछ पत्र भी प्रकाशित नहीं किया था लेकिन, उन्होंने बहुत कुछ हासिल कर लिया था। यांत्रिकी, प्रकाशिकी, और चुंबकत्व सहित अनुसंधान के कई क्षेत्रों, उनकी पांडुलिपियों में बड़े पैमाने पर प्रमुख थे, लेकिन वो शायद ही प्रकाशन के काम में शामिल थे। कैवेंडिश अठारहवीं और उन्नीसवीं सदी के तथाकथित वायवीय दवा की दुकानों में से एक माना जाता है, साथ में, उदाहरणार्थ, जोज़ेफ़ प्रीस्टलि, जोसेफ ब्लैक, और डैनियल रदरफोर्ड। मजबूत एसिड (strong acid) के साथ धातुओं के संयोजन से, कैवेंडिश हाइड्रोजन ने हाइड्रोजन (H2) बनाया — जिसे वह "ज्वलनशील हवा" कहा करते थे —एसिड में धातुओं में घुला देनेवाला के द्वारा। हालांकि दुसरे लोग, रॉबर्ट बॉयल की तरह, हाइड्रोजन गैस पहले से तैयार किया हुआ था, कैवेंडिश को आमतौर पर अपने मौलिक स्वभाव को पहचानने के लिए ऋण दिया जाता है। इसके अलावा, एसिड में क्षार भंग द्वारा, कैवेंडिश ने "निश्चित हवा" (कार्बन डाइऑक्साइड) बनाया, जिसे उन्होंने अन्य गैसों के साथ, पानी के ऊपर उलटे बोतल में या पारे में, एकत्रित किया। इसके बाद उन्होंने पानी में अपनी घुलनशीलता और उनके विशिष्ट गुरुत्व  मापा और उनके कामबस्टबीलिटी का उल्लेख किया। इस पत्र के लिए कैवेंडिश को रॉयल सोसाइटी कापले मैडल से सम्मानित किया गया था। गैस रसायन शास्त्र में 18 वीं सदी के उत्तरार्ध में बढ़ते महत्व का था और रसायन शास्त्र के फ्रांसीसी आँत्वाँ लाव्वाज़्ये के सुधार के लिए महत्वपूर्ण बन गया, आम तौर पर रासायनिक क्रांति के रूप में जाना जाता है।
1783 में कैवेंडिश ने एक कागज पर eudiometry (the measurement of the goodness of gases for breathing) प्रकाशित किया। वह अपने ही आविष्कार की एक नई युडियमेटर वर्णित किया, जिसके साथ उन्होंने तारीख तक सबसे अच्छा परिणाम हासिल किया, using what in other hands had been the inexact method of measuring gases by weighing them. उन्होंने अगला परिष्कृत हवा (अब ऑक्सीजन होने के लिए जाना जाता है) में ज्वलनशील हवा जलने से पानी के उत्पादन पर एक पत्र प्रकाशित किया (जोकि हाइड्रोजन है), बाद में वायुमंडलीय हवा के घटक (phlogiston theory) को प्रकाशित किया। कैवेंडिश ने निष्कर्ष निकाला कि sophisticated परिष्कृत हवा परिष्कृत पानी था और कहा कि हाइड्रोजन या तो शुद्ध ज्वलनशीलता या परिष्कृत पानी था। उन्होंने इन खोजो को जोज़ेफ़ प्रीस्टलि को सूचित किया, जोकि एक अंग्रेजी पादरी और वैज्ञानिक थे, मार्च 1783 से बाद से अधिक तक नहीं, लेकिन अगले वर्ष तक उन्हें प्रकाशित नहीं किया था। स्कॉटिश आविष्कारक जेम्स वाट ने 1783 में पानी की संरचना पर एक शोध पत्र प्रकाशित किया; कैवेंडिश ने प्रयोगों का प्रदर्शन पहले किया था लेकिन दूसरी बारी में प्रकाशित किया। प्राथमिकता के बारे में विवाद शुरू हो गयी।
1785 में कैवेंडिश आम हवा (यानी, वायुमंडलीय) की संरचना एक जांच से बाहर निकले, और प्रभावशाली सटीक परिणाम प्राप्त किया। उन्होंने हाइड्रोजन में प्रयोगों का आयोजन किया और साधारण हवा अनुपात में संयुक्त ज्ञात किया और फिर बिजली की एक चिंगारी के साथ विस्फोट किया। इसके अलावा, he also described an experiment in which he was able to remove, in modern terminology, both the oxygen and nitrogen gases from a sample of atmospheric air until only a small bubble of uncreated gas was left in the original sample. Using his observations, Cavendish observed that, when he had determined the amounts of phlogisticated air (nitrogen) and dephlogisticated air (oxygen), there remained a volume of gas amounting to 1/120 of the original volume of nitrogen. By careful measurements he was led to conclude that, "common air consists of one part of dephlogisticated air [oxygen], mixed with four of phlogisticated [nitrogen]".
In the 1890s (around 100 years later) two British physicists, William Ramsay and Lord Rayleigh, realized that their newly discovered inert gas, argon, was responsible for Cavendish's problematic residue; he had not made an error. What he had done was perform rigorous quantitative experiments, using standardized instruments and methods, aimed at reproducible results; taken the mean of the result of several experiments; and identified and allowed for sources of error. The balance that he used, made by a craftsman named Harrison, was the first of the precision balances of the 18th century, and as accurate as Lavoisier's (which has been estimated to measure one part in 400,000). Cavendish worked with his instrument makers, generally improving existing instruments rather than inventing wholly new ones.
Cavendish, as indicated above, used the language of the old phlogiston theory in chemistry. In 1787 he became one of the earliest outside France to convert to the new antiphlogistic theory of Lavoisier, though he remained skeptical about the nomenclature of the new theory. He also objected to Lavoisier's identification of heat as having a material or elementary basis. Working within the framework of Newtonian mechanism, Cavendish had tackled the problem of the nature of heat in the 1760s, explaining heat as the result of the motion of matter. In 1783 he published a paper on the temperature at which mercury freezes and in that paper made use of the idea of latent heat, although he did not use the term because he believed that it implied acceptance of a material theory of heat. He made his objections explicit in his 1784 paper on air. He went on to develop a general theory of heat, and the manuscript of that theory has been persuasively dated to the late 1780s. His theory was at once mathematical and mechanical; it contained the principle of the conservation of heat (later understood as an instance of conservation of energy) and even contained the concept (although not the label) of the mechanical equivalent of heat.

पृथ्वी का घनत्व

Following his father's death, Henry bought another house in town and also a house in Clapham Common, to the south of London. The London house contained the bulk of his library, while he kept most of his instruments at Clapham Common, where he carried out most of his experiments. The most famous of those experiments, published in 1798, was to determine the density of the Earth and became known as the Cavendish experiment. The apparatus Cavendish used for weighing the Earth was a modification of the torsion balance built by Englishman and geologist John Michell, who died before he could begin the experiment. The apparatus was sent in crates to Cavendish, who completed the experiment in 1797–1798 and published the results. The experimental apparatus consisted of a torsion balance with a pair of 2-inch 1.61-pound lead spheres suspended from the arm of a torsion balance and two much larger stationary lead balls (350 pounds). Cavendish intended to measure the force of gravitational attraction between the two. He noticed that Michell's apparatus would be sensitive to temperature differences and induced air currents so he made modifications by isolating the apparatus in a separate room with external controls and telescopes for making observations.
Using this equipment, Cavendish calculated the attraction between the balls from the period of oscillation of the torsion balance, and then he used this value to calculate the density of the Earth. Cavendish found that the Earth's average density is 5.48 times greater than that of water. John Henry Poynting later noted that the data should have led to a value of 5.448, and indeed that is the average value of the twenty-nine determinations Cavendish included in his paper. What was extraordinary about Cavendish’s experiment was its elimination of every source of error and every factor that could disturb the experiment and its precision in measuring an astonishingly small attraction, a mere 1/50,000,000 of the weight of the lead balls. The result that Cavendish obtained for the density of the Earth is within 1 percent of the currently accepted figure.
कैवेंडिश ने गुरुत्वाकर्षक स्थिरांक और पृथ्वी के द्रव्यमान के लिए सही मूल्यों को खोजा। उसके परिणामों के आधार पर, एक G के मूल्य की गणना जोकि 6.754 × 10⁻¹¹N-m²/kg2 है, जो आधुनिक मूल्य 6.67428 × 10−11N-m2/kg2 के साथ कृपापूर्वक तुलना करती है।
Books often describe Cavendish's work as a measurement of either the gravitational constant (G) or the Earth's mass. Since these are related to the Earth's density by a trivial web of algebraic relations, none of these sources are wrong, but they do not match the exact word choice of Cavendish, and this mistake has been pointed out by several authors. Cavendish's stated goal was to measure the Earth's density, although his result obviously calculates G in order to do so.
The first time that the constant got this name was in 1873, almost 100 years after the Cavendish experiment, but the constant was in use since the time of Newton. Cavendish's results obviously also give the Earth’s mass.

विद्युत अनुसंधान

Cavendish's electrical and chemical experiments, like those on heat, had begun while he lived with his father in a laboratory in their London house. Lord Charles Cavendish died in 1783, leaving almost all of his very substantial estate to Henry. Like his theory of heat, Cavendish's comprehensive theory of electricity was mathematical in form and was based on precise quantitative experiments. In 1771 he published an early version of his theory, based on an expansive electrical fluid that exerted pressure. He demonstrated that if the intensity of electric force was inversely proportional to distance, then the electric fluid in excess of that needed for electrical neutrality would lie on the outer surface of an electrified sphere; then he confirmed this experimentally. Cavendish continued to work on electricity after this initial paper, but he published no more on the subject.
Cavendish wrote papers on electrical topics for the Royal Society but the bulk of his electrical experiments did not become known until they were collected and published by James Clerk Maxwell a century later, in 1879, long after other scientists had been credited with the same results. Cavendish’s electrical papers from the Philosophical Transactions of the Royal Society of London have been reprinted, together with most of his electrical manuscripts, in The Scientific Papers of the Honourable Henry Cavendish, F.R.S. (1921). According to the 1911 edition of Encyclopædia Britannica, among Cavendish's discoveries were the concept of electric potential (which he called the "degree of electrification"), an early unit of capacitance (that of a sphere one inch in diameter), the formula for the capacitance of a plate capacitor, the concept of the dielectric constant of a material, the relationship between electric potential and current (now called Ohm's Law) (1781), laws for the division of current in parallel circuits (now attributed to Charles Wheatstone), and the inverse square law of variation of electric force with distance, now called Coulomb's Law.

मृत्यु

कैवेंडिश की 1810 में मृत्यु हो गई (ब्रिटेन में सबसे धनी लोगों में से एक के रूप में) और उन्हें अब डर्बी कैथेड्रल है कि चर्च में उनके कई पूर्वजों के साथ दफनाया गया था। वह डर्बी में पर रहते थे सड़क को बाद में उनका नाम दिया गया है। The University of Cambridge's Cavendish Laboratory was endowed by one of Cavendish's later relatives, William Cavendish, 7th Duke of Devonshire (Chancellor of the University from 1861 to 1891).

व्यक्तित्व और विरासत

Cavendish was a shy man who was uncomfortable in society and avoided it when he could. He conversed little, always dressed in an old-fashioned suit, and developed no known deep personal attachments outside his family. Cavendish was taciturn and solitary and regarded by many as eccentric. He only communicated with his female servants by notes. By one account, Cavendish had a back staircase added to his house in order to avoid encountering his housekeeper because he was especially shy of women. The contemporary accounts of his personality have led some modern commentators, such as Oliver Sacks, to speculate that he had Asperger syndrome, though he may merely have been anthropophobic.His only social outlet was the Royal Society Club, whose members dined together before weekly meetings. Cavendish seldom missed these meetings, and was profoundly respected by his contemporaries. However his shyness made those who "sought his views... speak as if into vacancy. If their remarks were...worthy, they might receive a mumbled reply, but more often than not they would hear a peeved squeak (his voice appears to have been high-pitched) and turn to find an actual vacancy and the sight of Cavendish fleeing to find a more peaceful corner". Cavendish's religious views were also considered eccentric for his time. He was considered to be agnostic. As his biographer, George Wilson, comments, "As to Cavendish's religion, he was nothing at all". He also enjoyed collecting fine furniture exemplified by his purchase of a set of "ten inlaid satinwood chairs with matching cabriole legged sofa".
Because of his asocial and secretive behaviour, Cavendish often avoided publishing his work, and much of his findings were not even told to his fellow scientists. In the late nineteenth century, long after his death, James Clerk Maxwell looked through Cavendish's papers and found things for which others had been given credit. Examples of what was included in Cavendish's discoveries or anticipations were Richter's law of reciprocal proportions, Ohm's law, Dalton's law of partial pressures, principles of electrical conductivity (including Coulomb's law), and Charles's law of gases. A manuscript "Heat", tentatively dated between 1783 and 1790, describes a "mechanical theory of heat". Hitherto unknown, the manuscript was analyzed in the early 21st century. Historian of science Russell McCormmach proposed that "Heat" is the only 18th century work prefiguring thermodynamics. Theoretical physicist Dietrich Belitz concluded that in this work Cavendish "got the nature of heat essentially right."
As Cavendish performed his famous density of the Earth experiment in an outbuilding in the garden of his Clapham Common estate, his neighbours would point out the building and tell their children that it was where the world was weighed. In honor of Henry Cavendish's achievements and due to an endowment granted by Henry's relative William Cavendish, 7th Duke of Devonshire, the University of Cambridge’s physics laboratory was named the Cavendish Laboratory by James Clerk Maxwell, the first Cavendish Professor of Physics and an admirer of Cavendish's work.