Biography

Biography
Albert Einstein was born at Ulm, in Württemberg, Germany, on March 14, 1879. Six weeks later the family moved to Munich and he began his schooling there at the Luitpold Gymnasium. Later, they moved to Italy and Albert continued his education at Aarau, Switzerland and in 1896 he entered the Swiss Federal Polytechnic School in Zurich to be trained as a teacher in physics and mathematics. In 1901, the year he gained his diploma, he acquired Swiss citizenship and, as he was unable to find a teaching post, he accepted a position as technical assistant in the Swiss Patent Office. In 1905 he obtained his doctor's degree.During his stay at the Patent Office, and in his spare time, he produced much of his remarkable work and in 1908 he was appointed Privatdozent in Berne. In 1909 he became Professor Extraordinary at Zurich, in 1911 Professor of Theoretical Physics at Prague, returning to Zurich in the following year to fill a similar post. In 1914 he was appointed Director of the Kaiser Wilhelm Physical Institute and Professor in the University of Berlin. He became a German citizen in 1914 and remained in Berlin until 1933 when he renounced his citizenship for political reasons and emigrated to America to take the position of Professor of Theoretical Physics at Princeton*. He became a United States citizen in 1940 and retired from his post in 1945.After World War II, Einstein was a leading figure in the World Government Movement, he was offered the Presidency of the State of Israel, which he declined, and he collaborated with Dr. Chaim Weizmann in establishing the Hebrew University of Jerusalem.Einstein always appeared to have a clear view of the problems of physics and the determination to solve them. He had a strategy of his own and was able to visualize the main stages on the way to his goal. He regarded his major achievements as mere stepping-stones for the next advance.At the start of his scientific work, Einstein realized the inadequacies of Newtonian mechanics and his special theory of relativity stemmed from an attempt to reconcile the laws of mechanics with the laws of the electromagnetic field. He dealt with classical problems of statistical mechanics and problems in which they were merged with quantum theory: this led to an explanation of the Brownian movement of molecules. He investigated the thermal properties of light with a low radiation density and his observations laid the foundation of the photon theory of light.In his early days in Berlin, Einstein postulated that the correct interpretation of the special theory of relativity must also furnish a theory of gravitation and in 1916 he published his paper on the general theory of relativity. During this time he also contributed to the problems of the theory of radiation and statistical mechanics.In the 1920's, Einstein embarked on the construction of unified field theories, although he continued to work on the probabilistic interpretation of quantum theory, and he persevered with this work in America. He contributed to statistical mechanics by his development of the quantum theory of a monatomic gas and he has also accomplished valuable work in connection with atomic transition probabilities and relativistic cosmology.After his retirement he continued to work towards the unification of the basic concepts of physics, taking the opposite approach, geometrisation, to the majority of physicists.Einstein's researches are, of course, well chronicled and his more important works include Special Theory of Relativity (1905), Relativity (English translations, 1920 and 1950), General Theory of Relativity (1916), Investigations on Theory of Brownian Movement (1926), and The Evolution of Physics (1938). Among his non-scientific works, About Zionism (1930), Why War? (1933), My Philosophy (1934), and Out of My Later Years (1950) are perhaps the most important.Albert Einstein received honorary doctorate degrees in science, medicine and philosophy from many European and American universities. During the 1920's he lectured in Europe, America and the Far East and he was awarded Fellowships or Memberships of all the leading scientific academies throughout the world. He gained numerous awards in recognition of his work, including the Copley Medal of the Royal Society of London in 1925, and the Franklin Medal of the Franklin Institute in 1935.Einstein's gifts inevitably resulted in his dwelling much in intellectual solitude and, for relaxation, music played an important part in his life. He married Mileva Maric in 1903 and they had a daughter and two sons; their marriage was dissolved in 1919 and in the same year he married his cousin, Elsa Löwenthal, who died in 1936. He died on April 18, 1955 at Princeton, New Jersey.
From Nobel Lectures, Physics 1901-1921, Elsevier Publishing Company, Amsterdam, 1967
This autobiography/biography was first published in the book series Les Prix Nobel. It was later edited and republished in Nobel Lectures. To cite this document, always state the source as shown above.
* Albert Einstein was formally associated with the Institute for Advanced Study located in Princeton, New Jersey.

Albert Einstein

Albert Einstein
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Albert Einstein
Nobel per la fisica 1921
Albert Einstein (Ulma, 14 marzo 1879 – Princeton, 18 aprile 1955) è stato un fisico e matematico tedesco naturalizzato svizzero, e in seguito statunitense.
Oltre a essere uno dei più celebri fisici e matematici della storia della scienza, fu un grande pensatore e attivista in molti altri ambiti (dalla filosofia alla politica). Per il suo complesso apporto alle scienze e alla fisica in particolare è indicato come uno dei più importanti studiosi del XX secolo.
Conosciuto soprattutto per le sue teorie sulla relatività ristretta e sulla relatività generale, diede anche importanti contributi alla nascita della meccanica quantistica e alla critica dei suoi fondamenti, alla meccanica statistica e alla cosmologia.
Ricevette il Premio Nobel per la Fisica nel 1921 grazie alla sua spiegazione dell'effetto fotoelettrico e "per i suoi contributi alla fisica teorica". Dopo la formulazione, nel novembre 1915, della teoria della Relatività generale la fama di Einstein dilagò in tutto il mondo. Era un successo insolito per uno scienziato e, durante gli ultimi anni della sua vita, la fama di Einstein non fece che aumentare, superando quella di qualunque altro scienziato della storia. Nella cultura popolare, il suo nome divenne ben presto sinonimo di intelligenza e di grande genio. La sua immagine rimane a tutt'oggi una delle più conosciute al mondo. Questa popolarità ha inoltre portato ad uso molto diffuso della sua immagine nel mondo della pubblicità, giungendo persino alla registrazione di "Albert Einstein" come marchio.
Indice[nascondi]
1 Biografia
1.1 Gioventù e studi liceali
1.2 Teoria della relatività ristretta
1.3 Teoria della relatività generale
1.4 Nobel nel 1921
1.5 Einstein filosofo
1.6 Visione politica
1.7 La visione religiosa
1.8 Curiosità
2 Einstein e il socialismo
3 Han detto di lui
4 Riferimenti
5 Altri progetti
6 Collegamenti esterni
//

[modifica] Biografia

[modifica] Gioventù e studi liceali

Il giovane Einstein
Albert Einstein nacque a Ulma nel Württemberg, in Germania; 100 km a est di Stoccarda. I suoi genitori erano Hermann Einstein, proprietario di una piccola azienda che produceva macchinari elettrici, e Pauline Koch. Si sposarono a Stuttgart-Bad Cannstatt. La famiglia era ebrea (non-osservante); Albert frequentò una scuola elementare cattolica e, su insistenza della madre, gli furono impartite lezioni di violino.
All'età di cinque anni, suo padre gli mostrò una bussola tascabile, e Einstein realizzò che qualcosa nello spazio "vuoto" agiva sull'ago spostandolo in direzione del nord; descriverà in seguito quest'esperienza come una delle più rivelatorie della sua vita. Benché abbia sviluppato modelli e dispositivi meccanici per divertimento, il suo ingresso nel mondo della scienza ufficiale avvenne abbastanza tardi, forse a causa della dislessia, della semplice timidezza, o della significativa rarità e particolarità della sua struttura cerebrale (il suo cervello fu esaminato dopo la sua morte). Più tardi egli stesso attribuì lo sviluppo della teoria della relatività a questa sua lentezza, dicendo che pensando allo spazio e al tempo più tardi della maggior parte dei bambini, fu in grado di applicarvi uno sviluppo intellettuale maggiore. Un'altra, più recente, teoria riguardo il suo sviluppo mentale è che soffrisse della sindrome di Asperger, una condizione simile all'autismo.
Einstein cominciò a studiare matematica all'età di dodici anni. La circostanza, riferita da alcuni, che il suo profitto in questa materia fosse scarso, non ha conferme storiche. Due suoi zii assecondarono i suoi interessi intellettuali durante la tarda infanzia e la prima adolescenza, aiutandolo negli studi e fornendogli libri di scienza e di matematica.
A causa dei continui problemi economici la famiglia Einstein dovette trasferirsi spesso, sin da quando il piccolo Albert non aveva nemmeno due mesi di vita; prima a Monaco, poi nel 1894 a Pavia, in Italia e, due anni dopo a Berna, in Svizzera.
Il suo fallimento all'esame d'ingresso presso il Politecnico di Zurigo (autunno 1895) fu una dura battuta d'arresto; fu mandato dalla sua famiglia a Aarau, in Svizzera, per concludere gli studi superiori, dove ricevette il diploma nel 1896. Nell'ottobre dello stesso anno tuttavia, superò l'esame di ammissione al Politecnico di Zurigo, vi si iscrisse e vi concluse i suoi studi con un esame ad agosto del 1900.
Nel 1898, Einstein incontrò e si innamorò di Mileva Marić, una sua compagna di studi serba (amica di Nikola Tesla). Mileva era l'unica donna ammessa a frequentare il Politecnico Federale svizzero e fu presentata da Tesla ad Einstein. Nel 1900 gli fu garantito un diploma da insegnante dall'Eidgenössische Technische Hochschule e fu accettato come cittadino svizzero nel 1901. In questo periodo Einstein discuteva dei suoi interessi scientifici con un ristretto gruppo di amici, inclusa Mileva. Lui e Mileva ebbero una figlia, Lieserl, nata nel gennaio 1902. I loro genitori erano contrari ad un loro matrimonio e considerarono la piccola Lieserl una figlia illegittima. La bambina morì di scarlattina.
Quel parto illegittimo compromise gli studi della giovane e promettente Mileva, che pure volontariamente decise di sacrificarsi per la famiglia e la carriera accademica di Albert.
Nel 1903, Albert e Mileva si sposarono in Municipio ed in seguito Mileva diede alla luce altri due figli.
Nel 1905 Einstein ottenne il dottorato mentre lavorava presso l'ufficio brevetti di Berna.

[modifica] Teoria della relatività ristretta
In quell'anno pubblicò l'articolo Zur Elektrodynamik bewegter Körper (Sull'elettrodinamica dei corpi in movimento), che aveva come oggetto l'interazione fra corpi carichi in movimento ed il campo elettromagnetico vista da diversi osservatori in stati di moto differenti.
Grazie a questo articolo, vennero risolte le controversie che avevano caratterizzato la fisica di fine '800 per quel che riguardava l'esistenza o meno di un sistema di riferimento assoluto. La teoria che ne scaturì fu indicata come teoria della Relatività ristretta.
Nello stesso 1905, pubblicò una nota che forniva una spiegazione dell'effetto fotoelettrico utilizzando il concetto di quanto, ipotizzato qualche anno prima da Max Planck. Questo lavoro diede una grande spinta alla meccanica quantistica, la cui concezione stava formandosi proprio in quegli anni. Ancora in quello stesso annus mirabilis sviluppò una teoria del moto browniano.
Dal 1908 insegnò a Berna e nel 1911 passò a Praga; nel 1914 fu nominato direttore dell'Istituto di Fisica dell'Università di Berlino, dove rimase fino al 1933. In quegli anni effettuò alcune ricerche sulla meccanica statistica e sulla teoria della radiazione, mentre stava concependo l'estensione delle teorie relativistiche.

[modifica] Teoria della relatività generale

L'eclissi del 1919 che verificò la veridicità della teoria della relatività generale
Il 1915 è un anno importante per la fisica teorica: in tale anno infatti, Einstein propose una teoria relativistica della gravitazione, indicata come Relatività generale, che descriveva le proprietà dello spazio-tempo a 4 dimensioni. In tale teoria si concludeva che i sistemi inerziali potevano avere senso solo in assenza di campi gravitazionali. Nonostante sia meno universalmente conosciuta e compresa, per le difficoltà del modello matematico usato per la descrizione, la relatività generale è una teoria molto più rivoluzionaria di quella ristretta, in quanto criticava alla base schemi universalmente accettati.
Inizialmente gli scienziati erano scettici perché la teoria derivava da ragionamenti matematici e analisi razionali, non da esperimenti o osservazioni. Ma nel 1919 le predizioni fatte dalla teoria furono confermate dalle misurazioni di Arthur Eddington durante un'eclissi solare, che verificarono che la luce emanata da una stella era deviata dalla Sole quando passava vicino ad esso. Le osservazioni furono effettuate il 29 maggio 1919 in due posti diversi, rispettivamente in Sobral, che si trova in Brasile, e nell'isola di Principe.
Nel 1917 mostrò il legame esistente tra la legge di Bohr e la formula di Planck dell'irraggiamento del corpo nero. Nello stesso anno introdusse la nozione di emissione stimolata, che sarebbe poi stata applicata alla concezione del laser.

[modifica] Nobel nel 1921
Nel 1921 ottenne il Premio Nobel per la Fisica (anche se diede la Nobel lecture nel 1922 essendo stato in viaggio in Giappone l'anno precedente) per il suo lavoro del 1905 sulla spiegazione dell'effetto fotoelettrico. In quegli anni Einstein cominciò a dedicarsi alla ricerca di teorie del campo unificate, argomento che lo appassionò fino alla fine, assieme ai tentativi di spiegazioni alternative dei fenomeni quantistici: infatti, la sua concezione del mondo fisico mal si conciliava con le interpretazioni probabilistiche della meccanica quantistica.
Si trasferì in America a causa delle persecuzioni antisemite che già imperversavano in Germania e in Europa.
Infatti quando Adolf Hitler salì al potere nel gennaio 1933, Einstein era professore ospite all'università di Princeton. Nel 1933 i Nazisti promulgarono "La Legge della Restaurazione del servizio Civile" a causa della quale tutti i professori universitari ebrei furono licenziati, e durante gli anni '30 fu condotta una campagna dai premi Nobel Philipp Lenard e Johannes Stark che etichettò i lavori di Einstein come "fisica ebrea", in contrasto con la "fisica tedesca" o "ariana". Einstein rinunciò alla cittadinanza tedesca e restò negli USA fino alla morte. All'Institute for Advanced Studies a Princeton proseguì con le sue ricerche, studiando anche alcuni problemi cosmologici e le
Refrigeratore
Diventò cittadino Americano nel 1940. Einstein nei suoi ultimi anni di vita tentò di unificare le forze fondamentali allora note, cioè la elettromagnetismo ignorando dell'esistenza della forza nucleare debole e della forza nucleare forte che verranno scoperte solo dopo la sua morte. Nel 1950 descrisse la sua teoria, poi rivelatasi parzialmente errata, in un articolo della rivista Scientific American.
Morì a Princeton nel 1955.

Einstein e Bohr
I vari lavori di Einstein operarono una rivoluzione di tale portata da poter essere paragonata solo con quella di Isaac Newton. La sua onestà scientifica si esplicitò nel dare impulso alla meccanica quantistica, tramite lo studio sull'effetto fotoelettrico, anche se non fu mai convinto del significato di quella teoria (famosa è la sua frase in polemica con Niels Bohr secondo cui Dio non gioca a dadi), non potendone accettare l'aspetto probabilistico. Tuttavia il campo in cui si applicò non riguarda solamente la relatività e gli studi ad essa collegati; vi è una parte della personalità di Einstein collegata ad un senso più pratico della scienza. Nel 1929 infatti lavorò assieme a Leo Szilard ad un prototipo di macchina refrigerante ad assorbimento diffusione realizzando un brevetto innovativo di un refrigeratore funzionante solo con una miscela di acqua e ammoniaca senza parti in movimento e con consumi elettrici bassissimi. Il brevetto non fu commercializzato perché fu soppiantato commercialmente dal brevetto Servel-Electrolux per gli attuali frigoriferi che noi tutti usiamo.

[modifica] Einstein filosofo
Questa sezione è solo un abbozzo. Se puoi, contribuisci adesso ad ampliarla.
Alla figura dello scienziato si affianca quella non meno importante di uomo calato nel suo tempo e di filosofo. Quanto era intransigente come scienziato, così lo fu come persona; nel 1913 rifiutò di firmare un manifesto a favore della guerra che gli veniva proposto da un buon numero di scienziati tedeschi.
Nel 1939, su sollecitazione di Leo Szilard, scrisse al presidente Roosevelt per sostenere l'opportunità che gli USA costruissero la bomba atomica, preoccupato della possibilità che il regime nazista potesse dotarsi per primo di quella terribile arma; successivamente invece non fu ascoltato quando nel 1945 si oppose al lancio della stessa bomba sul Giappone.

«Se dovessi rinascere, farei l'idraulico.»
(Albert Einstein, commentando la notizia del bombardamento atomico di Hiroshima.)
Fece poi sempre parte dei movimenti anti nucleari Americani.

[modifica] Visione politica
Einstein si considerò sempre un pacifista [1] ed un umanista [2], e negli ultimi anni della sua vita, anche socialista e accusato di essere comunista. Descrivendo il Mahatma Gandhi, Albert Einstein disse «Le future generazioni difficilmente potranno credere che qualcuno come lui sia stato sulla terra in carne ed ossa». «Gandhi, il più grande genio politico del nostro tempo, ci ha indicato la strada da percorrere. Egli ci ha mostrato di quali sacrifici l'uomo sia capace una volta che abbia scoperto il cammino giusto». «Dovremmo sforzarci di fare le cose allo stesso modo: non utilizzando la violenza per combattere per la nostra causa, ma non-partecipando a qualcosa che crediamo sia sbagliato». Le opinioni di Einstein su altri argomenti, come il socialismo, il maccartismo ed il razzismo, furono male interpretate e la sua figura risultò molto controversa negli Stati Uniti di quegli anni (vedi Einstein e il socialismo). Einstein fu inoltre co-fondatore del liberale Partito Democratico Tedesco.
L'FBI raccolse un fascicolo di 1427 pagine sulla sua attività e raccomandò che gli fosse impedito di emigrare negli Stati Uniti secondo lo Alien Exclusion Act, aggiungendo che, insieme ad altri addebiti, Einstein credeva, consigliava, difendeva o insegnava una dottrina che, in senso legale, era stata ritenuta dai tribunali, in altri casi, «capace di permettere all'anarchia di progredire indisturbata» e che portava a «un governo solo di nome». Aggiunse anche che Einstein «era stato membro, sostenitore o affiliato a 34 movimenti comunisti tra il 1937 ed il 1954» e che «inoltre lavorò come presidente onorario in tre organizzazioni comuniste»[3].

Einstein e il presidente del Comitato ebraico anti-fascista Sovietico Solomon Mikhoels, 1943
Einstein si oppose ai governi dittatoriali e per questo motivo (e per le sue origini ebraiche) si oppose al regime nazista e abbandonò la Germania subito dopo la presa del potere da parte del partito nazista. In principio fu favorevole alla costruzione della bomba atomica al fine di prevenirne la costruzione da parte di Hitler e per questo scrisse anche una lettera [4] (del 2 agosto del 1939 probabilmente scritta da Leo Szilard) al presidente Roosevelt incoraggiandolo ad iniziare un programma di ricerca per creare delle armi atomiche. Roosevelt rispose creando un comitato per studiare la possibilità di usare l'uranio come arma nucleare. Successivamente il Progetto Manhattan assorbì tale comitato.
Tuttavia, dopo la guerra, Einstein fece pressioni per il disarmo nucleare e per l'istituzione di un governo mondiale. Affermò: «Non so con quali armi verrà combattuta la III guerra mondiale ma la IV verrà combattuta con clave e pietre». Einstein non fu un sostenitore del sionismo anche se sostenne l'insediamento ebraico nell'antica sede del giudaismo e fu attivo nell'istituzione dell'università ebraica di Gerusalemme, in cui pubblicò (1930) un volume intitolato About Zionism: Discorsi e Conferenze del Professor Albert Einstein, e a cui donò i suoi scritti. D'altra parte si oppose al nazionalismo ed espresse scetticismo rispetto alla soluzione di uno stato-nazione ebraico. Infatti immaginava che gli ebrei e gli arabi non potessero vivere in pace nello stesso territorio. Insieme ad altri intellettuali ebrei (tra cui Hannah Arendt) il 4 dicembre 1948 scrisse una lettera al New York Times [5] in cui veniva fortemente criticata la visita negli Stati Uniti di Menachem Begin, definendo i metodi e l'ideologia del suo partito "Tnuat Haherut" (formato dopo lo scioglimento ufficiale dell'Irgun) come ispirati a quelli dei partiti fascisti. In tarda età ( 1952 ) gli fu offerto il posto di secondo capo di stato del nuovo stato di Israele ma declinò l'invito con la scusa di non avere le capacità necessarie.
Einstein, insieme ad Albert Schweitzer ed a Bertrand Russell, combatté contro i test e le sperimentazioni militari della bomba atomica.
Insieme a Russell firmò il Manifesto Russell-Einstein che dette vita alla Conferenza di Pugwash per la Scienza e gli Interessi del Mondo.

[modifica] La visione religiosa
Benché fosse stato cresciuto come ebreo, Einstein non credeva negli aspetti religiosi dell'ebraismo ma considerava se stesso ebreo da un punto di vista etnico.
A differenza di quanto a volte sostenuto, non credeva in un Dio personale. Infatti in una lettera personale nel 1954 scriveva:

«Io non credo in un Dio personale e non l'ho mai negato, anzi, ho sempre espresso le mie convinzioni chiaramente. Se qualcosa in me può essere chiamato religioso è la mia sconfinata ammirazione per la struttura del mondo che la scienza ha fin qui potuto rivelare. »
Alcuni storici hanno visto nelle parole che seguono una sorta di panteismo scientifico legato ai suoi studi di fisica:

« Io credo nel Dio di Spinoza che si rivela nella ordinaria armonia di ciò che esiste, non in un Dio che si preoccupa del fato e delle azioni degli esseri umani.»
Einstein era associato onorario della Rationalist Press Association sin dal 1934.
Il pensiero sulla morte:

« Non riesco a concepire un Dio che premi e castighi le sue creature o che sia dotato di una volontà simile alla nostra. E neppure riesco né voglio concepire un individuo che sopravviva alla propria morte fisica; lasciamo ai deboli di spirito, animati dal timore o da un assurdo egocentrismo, il conforto di simili pensieri. Sono appagato dal mistero dell'vita e dal barlume della meravigliosa struttura del mondo esistente, insieme al tentativo ostinato di comprendere una parte, sia pur minuscola, della Ragione che si manifesta nella Natura»

[modifica] Curiosità
La personalità eccentrica di Einstein lo ha legato a numerosissime curiosità e aneddoti; tuttavia molti degli aneddoti e delle citazioni a lui attribuite sono falsi oppure sono stati romanzati a tal punto da non aver più nessun contatto con i fatti reali. Di seguito sono riportate alcune delle curiosità più significative.
Einstein divenne vegetariano negli ultimi anni della sua vita.
Poiché la sua famiglia visse per alcuni anni in Italia, Einstein parlava un discreto italiano.
Incontrò solo una volta il matematico Gregorio Ricci-Curbastro creatore degli strumenti di analisi tensoriale necessari alla formulazione matematica della relatività generale.
Durante la sua permanenza a Princeton negli anni cinquanta Einstein strinse amicizia con il matematico Kurt Gödel. Pur avendo un temperamento estremamente diverso da lui, Einstein amava poter parlare nella propria lingua madre.
Ad Einstein è dedicato un asteroide: 2001 Einstein.
Una citazione probabilmente apocrifa[1], sulla sua esperienza in Germania nel primo dopoguerra, fra rivoluzione repressa e vittoria del nazismo, è la seguente:

«Essendo un amante della libertà, quando avvenne la rivoluzione in Germania, guardai con fiducia alle università sapendo che queste si erano sempre vantate della loro devozione alla causa della verità. Ma le università vennero zittite. Allora guardai ai grandi editori dei quotidiani che in ardenti editoriali proclamavano il loro amore per la libertà. Ma anche loro, come le università vennero ridotti al silenzio, soffocati nell'arco di poche settimane. Solo la Chiesa rimase ferma in piedi a sbarrare la strada alle campagne di Hitler per sopprimere la verità. Io non ho mai provato nessun interesse particolare per la Chiesa prima, ma ora provo nei suoi confronti grande affetto e ammirazione, perché la Chiesa da sola ha avuto il coraggio e l'ostinazione per sostenere la verità intellettuale e la libertà morale. Devo confessare che ciò che io una volta disprezzavo, ora lodo incondizionatamente.»
(Dichiarazione di Albert Einstein pubblicata da Time magazine, 23 dicembre 1940, pag. 40)

[modifica] Einstein e il socialismo
Nell'articolo del 1949 "perché il socialismo?", Albert Einstein descrisse l'anarchia economica della società capitalistica moderna come fonte di un male da superare. Egli era contrario ai regimi totalitari dell'Unione Sovietica e di altri paesi, ma era favorevole ad un socialismo democratico che combinasse un'economia pianificata con un profondo rispetto per i diritti umani. Difatti per Einstein il vero scopo del socialismo era precisamente di superare e andare al di là della "fase predatoria dello sviluppo umano" per anticipare un modello di società nuovo che conciliasse il benessere del singolo individuo con quello della comunità intera.

[modifica] Han detto di lui

«È vivace, sicuro di sé, piacevole. Di psicologia ne capisce quanto me di fisica, tanto che abbiamo avuto una conversazione molto scherzosa.»
(Sigmund Freud, 1926)

[modifica] Riferimenti
↑ Sembra che Einstein avesse semplicemente affermato che ben pochi intellettuali, tranne qualche uomo di chiesa, si fosse preoccupato della limitazione delle libertà individuali e intellettuali, e che questa affermazione venne ingigantita. Vedi en.wikiquote

[modifica] Altri progetti
Wikiquote
Commons
Wikiquote contiene citazioni di o su Albert Einstein
Commons contiene file multimediali su Albert Einstein

[modifica] Collegamenti esterni
3000 scritti messi online il 13 marzo 2003
Nobel e-Museum
DISF, sul rapporto di Einstein con la religione a cura di T.F. Torrance
Perché il socialismo? (il manoscritto tradotto in italiano)
(EN) Albert Einstein
Why socialism? - Albert Einstein, Monthly review, 1949-05 (il manoscritto originale).
(EN) FBI Freedom of Information Act Documents on Einstein
Estratto da "http://it.wikipedia.org/wiki/Albert_Einstein"

Collected Papers of Albert Einstein

Collected Papers of Albert Einstein
The Collected Papers of Albert Einstein is one of the most ambitious publishing ventures ever undertaken in the documentation of the history of science. Selected from among more than 40,000 documents contained in the personal collection of Albert Einstein (1879-1955), and 15,000 Einstein and Einstein-related documents discovered by the editors since the beginning of the Einstein Project, The Collected Papers will provide the first complete picture of a massive written legacy that ranges from Einstein's first work on the special and general theories of relativity and the origins of quantum theory, to expressions of his profound concern with civil liberties, education, Zionism, pacifism, and disarmament. The series will contain over 14,000 documents and will fill twenty-five volumes. Sponsored by the Hebrew University of Jerusalem and Princeton University Press, the Einstein project was located at and supported by Boston University from 1986 to 2000. Currently located at and supported by The California Institute of Technology, the project will continue to make available a monumental collection of primary material. The Albert Einstein Archives are located at the Hebrew University of Jerusalem.
About The Series
After Volume 1, the papers divide into two series, with the documents in each volume presented in chronological order. One series, the Writings, will include such items as Einstein's published and unpublished articles, lecture and research notebooks, book reviews, patent applications, and available accounts of his lectures, speeches, interviews, and other oral statements. The other series, the Correspondence, will include a wide selection of letters written by and to Einstein, as well as significant documents about him by third parties. The Correspondence volumes will also contain calendars of Einstein's life for the years covered. The two series will be extensively cross-referenced.
Every document in The Collected Papers will appear in the language in which it was written, while the introduction, headnotes, footnotes, and other scholarly apparatus will be in English. Upon release of each volume, Princeton University Press will also publish an English translation of previously untranslated non-English documents.
Volume 1.. The Early Years, 1879-1902. A. Einstein; J. Stachel, D.C. Cassidy, et al., eds.
Volume 1. (English). The Early Years, 1879-1902. (English translation supplement). A. Einstein; A. Beck, trans.
Volume 2.. The Swiss Years: Writings, 1900-1909. A. Einstein; J. Stachel, D.C. Cassidy, et al., eds.
Volume 2. (English). The Swiss Years: Writings, 1900-1909. (English translation supplement). A. Einstein; A. Beck, trans.
Volume 3.. The Swiss Years: Writings, 1909-1911. A. Einstein; M.J. Klein, A.J. Kox, et al., eds.
Volume 3. (English). The Swiss Years: Writings, 1909-1911. (English translation supplement). A. Einstein; A. Beck, trans.
Volume 4.. The Swiss Years: Writings, 1912-1914. A. Einstein; M.J. Klein, A.J. Kox, et al., eds.
Volume 4. (English). The Swiss Years: Writings, 1912-1914. (English translation supplement). A. Einstein; D. Howard, trans.
Volume 5.. The Swiss Years: Correspondence, 1902-1914. A. Einstein; M.J. Klein, A.J. Kox, et al., eds.
Volume 5. (English). The Swiss Years: Correspondence, 1902-1914. (English translation supplement). A. Einstein; A. Beck, trans.
Volume 6.. The Berlin Years: Writings, 1914-1917. A. Einstein; A.J. Kox, M.J. Klein, et al., eds.
Volume 6. (English). The Berlin Years: Writings, 1914-1917. (English translation supplement). A. Einstein; A. Engel, trans.
Volume 7.. The Berlin Years: Writings, 1918-1921. A. Einstein; M. Janssen, R. Schulmann, et al., eds.
Volume 7. (English). The Berlin Years: Writings, 1918-1921. (English translation of selected texts). A. Einstein; A. Engel, trans.
Volume 8.. The Berlin Years: Correspondence, 1914-1918. A. Einstein; R. Schulmann, A.J. Kox, et al., eds.
Volume 8. (English). The Berlin Years: Correspondence, 1914-1918. (English supplement translation.). A. Einstein; A. Hentschel, trans.
Volume 9.. The Berlin Years: Correspondence, January 1919 - April 1920. A. Einstein; D. Buchwald, R. Schulmann, et al., eds.
Volume 9. (English). The Berlin Years: Correspondence, January 1919 - April 1920. (English translation of selected texts). A. Einstein; A. Hentschel, trans.
Volume 10. The Berlin Years: Correspondence, May-December 1920, and Supplementary Correspondence, 1909-1920. A. Einstein; D. Buchwald, T. Sauer, et al., eds.
Volume 10. (English). The Berlin Years: Correspondence, May-December 1920, and Supplementary Correspondence, 1909-1920. (English translation of selected texts). D. Buchwald, T. Sauer, et al., eds.

What hasn't Einstein's equation touched in our world?

What hasn't Einstein's equation touched in our world?
It's difficult to separate the enormous legacy of E = mc2 from Einstein's legacy as a whole. After all, the equation grew directly out of Einstein's work on special relativity, which is a subset of what most consider his greatest achievement, the theory of general relativity. But I'm going to give it a try nevertheless.
The equation explained
First, though, a capsule explanation of "energy equals mass times the speed of light squared" might be helpful. On the most basic level, the equation says that energy and mass (matter) are interchangeable; they are different forms of the same thing. Under the right conditions, energy can become mass, and vice versa. We humans don't see them that way—how can a beam of light and a walnut, say, be different forms of the same thing?—but Nature does.
So why would you have to multiply the mass of that walnut by the speed of light to determine how much energy is bound up inside it? The reason is that whenever you convert part of a walnut or any other piece of matter to pure energy, the resulting energy is by definition moving at the speed of light. Pure energy is electromagnetic radiation—whether light or X-rays or whatever—and electromagnetic radiation travels at a constant speed of roughly 670,000,000 miles per hour.
Why, then, do you have to square the speed of light? It has to do with the nature of energy. When something is moving four times as fast as something else, it doesn't have four times the energy but rather 16 times the energy—in other words, that figure is squared. So the speed of light squared is the conversion factor that decides just how much energy lies captured within a walnut or any other chunk of matter. And because the speed of light squared is a huge number—448,900,000,000,000,000 in units of mph—the amount of energy bound up into even the smallest mass is truly mind-boggling (see The Power of Tiny Things.)
Of course, intuitively understanding that energy and matter are essentially one, as well as why and how so much energy can be wrapped up in even minute bits of matter, is another thing. And E = mc2, which focuses on matter at rest, is a simplified version of a more elaborate equation that Einstein devised, which also takes into account matter in motion (more on that in a moment). But I hope that you, like I, now have a basic comprehension with which to appreciate the equation's prodigious influence.
E = mc2 in miniature
Perhaps the equation's most far-reaching legacy is that it provides the key to understanding the most basic natural processes of the universe, from microscopic radioactivity to the big bang itself.
Radioactivity is E = mc2 in miniature. Einstein himself suspected this even as he devised the equation. In the 1905 paper in which he introduced E = mc2 to the world, he suggested that it might be possible to test his theory about the equation using radium, an ounce of which, as Marie Curie had discovered not long before, continuously emits 4,000 calories of heat per hour. Einstein believed that radium was constantly converting part of its mass to energy exactly as his equation specified. He was eventually proved right.
Today we know radioactivity to be a property possessed by some unstable elements, such as uranium, or isotopes, such as carbon 14, of spontaneously emitting energetic particles as their atomic nuclei disintegrate. They are metamorphosing mass into energy in direct accordance with Einstein's equation.
We take advantage of that realization today in many technologies. PET scans and similar diagnostics used in hospitals, for example, make use of E = mc2. "Whenever you use a radioactive substance to illuminate processes in the human body, you're paying direct homage to Einstein's insight," says Sylvester James Gates, a physicist at the University of Maryland. Many everyday devices, from smoke detectors to exit signs, also host an ongoing, invisible fireworks of E = mc2 transformations. Radiocarbon dating, which archeologists use to date ancient material, is yet another application of the formula. "The decay products that we see in carbon dating—that energy is directly obtained from the missing mass that you see in E = mc2," Gates says.
Heavenly applications
Space technologies owe much to the equation. Unceasing E = mc2 disintegrations from radioactive elements such as plutonium provide everything from power for telecommunications satellites to the heat needed to keep the Mars rovers functioning during the frigid martian winter. Space travel in the distant future may also rely on such radiation-derived power. Photons streaming out from the sun and other stars hold energy that in the vacuum of space can theoretically be harnessed to propel a spaceship. "In the far future," says David Hogg, a cosmologist at New York University, "if you imagine that we're sailing to distant stars with spaceships that are driven by radiation pressure—if that ever happens, that will be a really big legacy of Einstein's kinematics."
Kinematics is the study of motion without reference to mass or force, and it figures in a more elaborate form of Einstein's equation that—unlike plain old E = mc2, which concerns mass at rest—also takes into account mass in motion. (If you must know, it's E2 = m2c4 + p2c2, where p equals momentum.) "His bigger equation plays an enormous part in our understanding of how light works, and how energy and light can be transferred and transformed from one place to another, and that sort of thing," Gates says. "So if you consider the larger context, the part of the equation that's not in the public eye, it has an even larger legacy in science."
One application that draws on this larger equation, Gates says, is the giant neutrino detector now being built in Antarctica. Sunk deep in the ice, it will detect the eerie blue light, known as Cherenkov radiation, that is given off by neutrinos. Neutrinos are subatomic particles so lacking in mass that they pass straight through the Earth unscathed. Studying their light helps cosmologists better understand these mysterious particles and their distant sources, which may include black holes. Thus, says Gates, "as part of the equation's legacy, we'll be using the ice of Antarctica to look at neutrinos and other objects coming from outer space. And without knowing the relationship between the energy, momentum, and mass, that would be inconceivable to do. In fact, it was the use of this equation that led to the realization that neutrinos must exist."
A nuclear world
Einstein's equation also perfectly describes what's happening when we produce nuclear energy. As Arlin Crotts, a professor of astronomy at Columbia University, puts it, "our entire understanding of nuclear processes would be sort of lost without it." Fission reactors in nuclear power plants generate electricity by unlocking the energy tied up in fissionable materials. Fusion also furnishes energy from mass just as the equation posits. When two hydrogen atoms fuse to form a helium atom, the mass of the resulting helium is less than the two hydrogens, with the missing mass manifesting itself as fusion energy. Nuclear weapons, too, operate on the principle defined by the equation. Indeed, the mushroom cloud of an atomic bomb explosion is E = mc2 made visible.
“One of its legacies is very sociological: it just captures the imagination of everyone.”
The equation spawned a whole new branch of science—high-energy particle physics. Labs that work in this field thrive on E = mc2 conversions. In fact, proper design of particle accelerators, as well as analysis of the high-speed collisions within them, would be impossible without a thorough comprehension of the equation. Within accelerators, colliding particles are constantly vanishing, leaving only energy, and dollops of energy are constantly transmuting into newly fashioned particles. "Our species has repeatedly used an understanding of the equation to convert E into new forms of m that had never previously been seen," Gates says. "One of the outposts of science for the next century may well be whether the E includes super-E, and m includes super-m—new forms of energy and matter called 'super-partners.'"
A grasp of the equivalence of mass and energy also comes in handy when studying antimatter. When a particle meets its antiparticle, they annihilate eachother, leaving only a pulse of energy; by the same token, a high-energy photon can suddenly become a particle-antiparticle pair. Altogether, says Hogg, "E = mc2 has been very important in diagnosing and understanding properties of antimatter."
Einstein's formula also accounts for the heat in our planet's crust, which is kept warm by a steady barrage of E = mc2 conversions occurring within unstable radioactive elements such as uranium and thorium. "When they decay, some of the mass is lost and a little energy is created, and that keeps the crust warm," says John Rigden, a physicist at Washington University in St. Louis and author of Einstein 1905: The Standard of Greatness (Harvard, 2005). "So the temperature of the outer Earth, the crustal matter, is directly related to E = mc2."
A cosmological constant
A similar process happens far beyond Earth, inside stars. The warmth we feel from the sun, for example, is the result of the energy generated as hydrogen deep within our star continuously fuses to form helium. And stars don't stop there. When they exhaust their hydrogen, they begin to burn new fuels and create new elements, which are spewed out into the universe when the stars eventually explode, as burnt-out stars are wont to do. "The carbon, oxygen, nitrogen, and hydrogen that make up living organisms were baked in the innards of a star," Rigden says. "In terms of what goes on in stars, we owe our existence to E = mc2."
Einstein's equation even tells of what transpires at black holes, which can contain the mass of millions of stars. Here, E = mc2 is taking place on an astronomical—and highly efficient—scale. "In a nuclear process, you convert something like one part in 1,000 of your rest mass into energy, whereas if you fall into a black hole, you can convert something like 20, 30, 40 percent," Hogg says. "So from the point of view of the energetics of the universe, these black holes are important, because they are big converters of rest mass into energy."
On the largest scale of all—the beginning of the universe—E = mc2 is the only accepted explanation for what was going on. In the first seconds after the big bang, energy and matter went back and forth indiscriminately in exact accordance with the equation. "The description of how the big bang unfolds would be much, much different if you couldn't interconvert mass to energy," Crotts says. If it weren't for E = mc2, the universe would have ended up with a completely different collection of particles than we have now. "I'm not sure what we would have, but we definitely wouldn't be here," he says.
Intangible aspects
The equation's legacy extends into realms well beyond the scientific. David Hogg finds it very useful in teaching, for instance. "I use the equation a lot in class because it's the one equation that all students have definitely heard of," he says. "So one of its legacies is very sociological: it just captures the imagination of everyone." It also helps students remember the units of energy. "A joule is a kilogram meter squared per second squared, and the way you remember that is E = mc2," he says.
Arlin Crotts notes the world Einstein's equation opened up for us. "It just laid bare the fact that all this stuff lying around us is potentially a tremendous reservoir of energy, almost beyond the imagination, if only we could devise ways to get at it," he says. "And that's just an amazing fact." For John Rigden, the equation and Einstein's other leaps of imagination revealed how scientists can be just as visionary as artists, writers, and other "creative" types. "What he did," Rigden says, "has all the creativity in it of Absalom, Absalom or Monet's lily pads."
Jim Gates seconds that. Until Einstein's time, scientists typically would observe things, record them, then find a piece of mathematics that explained the results, he says. "Einstein exactly reverses that process. He starts off with a beautiful piece of mathematics that's based on some very deep insights into the way the universe works and then, from that, makes predictions about what ought to happen in the world. It's a stunning reversal to the usual ordering in which science is done. So that's one of the legacies, that we've learned the power of human creativity in the sciences—or, as Einstein himself might have said, 'to know the mind of God.'"
In the end, the equation's influence, on both scientific and sociological fronts, is indeed hard to separate from Einstein's influence as a whole—which, like E = mc2-derived heat from the sun, shows no sign of

An Einstein story

An Einstein story
A comment from Clive J. Grant reads:
I'm not permitted to tell you what lay behind it, but I traveled to Princeton, in the company of a textile expert, to discuss something with Einstein. What I remember is that he said,
If I give you a pfennig, you will be one pfennig richer and I'll be one pfennig poorer. But if I give you an idea, you will have a new idea but I shall still have it, too. I never did get the idea, but I did get the aphorism.

General relativity

General relativity
Mathematical Physics index
History Topics IndexVersion for printing
General relativity is a theory of gravitation and to understand the background to the theory we have to look at how theories of gravitation developed. Aristotle's notion of the motion of bodies impeded understanding of gravitation for a long time. He believed that force could only be applied by contact; force at a distance being impossible, and a constant force was required to maintain a body in uniform motion.
Copernicus's view of the solar system was important as it allowed sensible consideration of gravitation. Kepler's laws of planetary motion and Galileo's understanding of the motion and falling bodies set the scene for Newton's theory of gravity which was presented in the Principia in 1687. Newton's law of gravitation is expressed by
F = G M1M2/d2
where F is the force between the bodies of masses M1, M2 and d is the distance between them. G is the universal gravitational constant.
After receiving their definitive analytic form from Euler, Newton's axioms of motion were reworked by Lagrange, Hamilton, and Jacobi into very powerful and general methods, which employed new analytic quantities, such as potential, related to force but remote from everyday experience. Newton's universal gravitation was considered proved correct, thanks to the work of Clairaut and Laplace. Laplace looked at the stability of the solar system in Traité du Mécanique Céleste in 1799. In fact the so-called three-body problem was extensively studied in the 19th Century and was not properly understood until much later. The study of the gravitational potential allowed variations in gravitation caused by irregularities in the shape of the earth to be studied both practically and theoretically. Poisson used the gravitational potential approach to give an equation which, unlike Newton's, could be solved under rather general conditions.
Newton's theory of gravitation was highly successful. There was little reason to question it except for one weakness which was to explain how each of the two bodies knew the other was there. Some profound remarks about gravitation were made by Maxwell in 1864. His major work A dynamical theory of the electromagnetic field (1864) was written
... to explain the electromagnetic action between distant bodies without assuming the existence of forces capable of acting directly at sensible distances.
At the end of the work Maxwell comments on gravitation.
After tracing to the action of the surrounding medium both the magnetic and the electric attractions and repulsions, and finding them to depend on the inverse square of the distance, we are naturally led to inquire whether the attraction of gravitation, which follows the same law of the distance, is not also traceable to the action of a surrounding medium.
However Maxwell notes that there is a paradox caused by the attraction of like bodies. The energy of the medium must be decreased by the presence of the bodies and Maxwell said
As I am unable to understand in what way a medium can possess such properties, I cannot go further in this direction in searching for the cause of gravitation.
In 1900 Lorentz conjectured that gravitation could be attributed to actions which propagate with the velocity of light. Poincaré, in a paper in July 1905 (submitted days before Einstein's special relativity paper), suggested that all forces should transform according the Lorentz transformations. In this case he notes that Newton's law of gravitation is not valid and proposed gravitational waves which propagated with the velocity of light.
In 1907, two years after proposing the special theory of relativity, Einstein was preparing a review of special relativity when he suddenly wondered how Newtonian gravitation would have to be modified to fit in with special relativity. At this point there occurred to Einstein, described by him as the happiest thought of my life , namely that an observer who is falling from the roof of a house experiences no gravitational field. He proposed the Equivalence Principle as a consequence:-
... we shall therefore assume the complete physical equivalence of a gravitational field and the corresponding acceleration of the reference frame. This assumption extends the principle of relativity to the case of uniformly accelerated motion of the reference frame.
After the major step of the equivalence principle in 1907, Einstein published nothing further on gravitation until 1911. Then he realised that the bending of light in a gravitational field, which he knew in 1907 was a consequence of the equivalence principle, could be checked with astronomical observations. He had only thought in 1907 in terms of terrestrial observations where there seemed little chance of experimental verification. Also discussed at this time is the gravitational redshift, light leaving a massive body will be shifted towards the red by the energy loss of escaping the gravitational field.
Einstein published further papers on gravitation in 1912. In these he realised that the Lorentz transformations will not apply in this more general setting. Einstein also realised that the gravitational field equations were bound to be non-linear and the equivalence principle appeared to only hold locally.
This work by Einstein prompted others to produce gravitational theories. Work by Nordström, Abraham and Mie was all a consequence of Einstein's, so far failed, attempts to find a satisfactory theory. However Einstein realised his problems.
If all accelerated systems are equivalent, then Euclidean geometry cannot hold in all of them.
Einstein then remembered that he had studied Gauss's theory of surfaces as a student and suddenly realised that the foundations of geometry have physical significance. He consulted his friend Grossmann who was able to tell Einstein of the important developments of Riemann, Ricci (Ricci-Curbastro) and Levi-Civita. Einstein wrote
... in all my life I have not laboured nearly so hard, and I have become imbued with great respect for mathematics, the subtler part of which I had in my simple-mindedness regarded as pure luxury until now.
In 1913 Einstein and Grossmann published a joint paper where the tensor calculus of Ricci and Levi-Civita is employed to make further advances. Grossmann gave Einstein the Riemann-Christoffel tensor which, together with the Ricci tensor which can be derived from it, were to become the major tools in the future theory. Progress was being made in that gravitation was described for the first time by the metric tensor but still the theory was not right. When Planck visited Einstein in 1913 and Einstein told him the present state of his theories Planck said
As an older friend I must advise you against it for in the first place you will not succeed, and even if you succeed no one will believe you.
Planck was wrong, but only just, for when Einstein was to succeed with his theory it was not readily accepted. It was the second half of 1915 that saw Einstein finally put the theory in place. Before that however he had written a paper in October 1914 nearly half of which is a treatise on tensor analysis and differential geometry. This paper led to a correspondence between Einstein and Levi-Civita in which Levi-Civita pointed out technical errors in Einstein's work on tensors. Einstein was delighted to be able to exchange ideas with Levi-Civita whom he found much more sympathetic to his ideas on relativity than his other colleagues.
At the end of June 1915 Einstein spent a week at Göttingen where he lectured for six 2 hour sessions on his (incorrect) October 1914 version of general relativity. Hilbert and Klein attended his lectures and Einstein commented after leaving Göttingen
To my great joy, I succeeded in convincing Hilbert and Klein completely.
The final steps to the theory of general relativity were taken by Einstein and Hilbert at almost the same time. Both had recognised flaws in Einstein's October 1914 work and a correspondence between the two men took place in November 1915. How much they learnt from each other is hard to measure but the fact that they both discovered the same final form of the gravitational field equations within days of each other must indicate that their exchange of ideas was helpful.
On the 18th November he made a discovery about which he wrote For a few days I was beside myself with joyous excitement . The problem involved the advance of the perihelion of the planet Mercury. Le Verrier, in 1859, had noted that the perihelion (the point where the planet is closest to the sun) advanced by 38" per century more than could be accounted for from other causes. Many possible solutions were proposed, Venus was 10% heavier than was thought, there was another planet inside Mercury's orbit, the sun was more oblate than observed, Mercury had a moon and, really the only one not ruled out by experiment, that Newton's inverse square law was incorrect. This last possibility would replace the 1/d2 by 1/dp, where p = 2+ for some very small number . By 1882 the advance was more accurately known, 43'' per century. From 1911 Einstein had realised the importance of astronomical observations to his theories and he had worked with Freundlich to make measurements of Mercury's orbit required to confirm the general theory of relativity. Freundlich confirmed 43" per century in a paper of 1913. Einstein applied his theory of gravitation and discovered that the advance of 43" per century was exactly accounted for without any need to postulate invisible moons or any other special hypothesis. Of course Einstein's 18 November paper still does not have the correct field equations but this did not affect the particular calculation regarding Mercury. Freundlich attempted other tests of general relativity based on gravitational redshift, but they were inconclusive.
Also in the 18 November paper Einstein discovered that the bending of light was out by a factor of 2 in his 1911 work, giving 1.74". In fact after many failed attempts (due to cloud, war, incompetence etc.) to measure the deflection, two British expeditions in 1919 were to confirm Einstein's prediction by obtaining 1.98" 0.30" and 1.61" 0.30".
On 25 November Einstein submitted his paper The field equations of gravitation which give the correct field equations for general relativity. The calculation of bending of light and the advance of Mercury's perihelion remained as he had calculated it one week earlier.
Five days before Einstein submitted his 25 November paper Hilbert had submitted a paper The foundations of physics which also contained the correct field equations for gravitation. Hilbert's paper contains some important contributions to relativity not found in Einstein's work. Hilbert applied the variational principle to gravitation and attributed one of the main theorem's concerning identities that arise to Emmy Noether who was in Göttingen in 1915. No proof of the theorem is given. Hilbert's paper contains the hope that his work will lead to the unification of gravitation and electromagnetism.
In fact Emmy Noether's theorem was published with a proof in 1918 in a paper which she wrote under her own name. This theorem has become a vital tool in theoretical physics. A special case of Emmy Noether's theorem was written down by Weyl in 1917 when he derived from it identities which, it was later realised, had been independently discovered by Ricci in 1889 and by Bianchi (a pupil of Klein) in 1902.
Immediately after Einstein's 1915 paper giving the correct field equations, Karl Schwarzschild found in 1916 a mathematical solution to the equations which corresponds to the gravitational field of a massive compact object. At the time this was purely theoretical work but, of course, work on neutron stars, pulsars and black holes relied entirely on Schwarzschild's solutions and has made this part of the most important work going on in astronomy today.
Einstein had reached the final version of general relativity after a slow road with progress but many errors along the way. In December 1915 he said of himself
That fellow Einstein suits his convenience. Every year he retracts what he wrote the year before.
Most of Einstein's colleagues were at a loss to understand the quick succession of papers, each correcting, modifying and extending what had been done earlier. In December 1915 Ehrenfest wrote to Lorentz referring to the theory of November 25, 1915. Ehrenfest and Lorentz corresponded about the general theory of relativity for two months as they tried to understand it. Eventually Lorentz understood the theory and wrote to Ehrenfest saying I have congratulated Einstein on his brilliant results . Ehrenfest responded
Your remark "I have congratulated Einstein on his brilliant results" has a similar meaning for me as when one Freemason recognises another by a secret sign.
In March 1916 Einstein completed an article explaining general relativity in terms more easily understood. The article was well received and he then wrote another article on relativity which was widely read and went through over 20 printings.
Today relativity plays a role in many areas, cosmology, the big bang theory etc. and now has been checked by experiment to a high degree of accuracy.References (29 books/articles)
Other Web sites:Astroseti (A Spanish translation of this article)
Article by: J J O'Connor and E F Robertson
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