Albert Einstein was a
theoretical physicistTheoretical physics is a branch of physics which employs mathematical models and abstractions of physics in an attempt to explain natural phenomena. Its central core is mathematical physics,[Sometimes mathematical physics and theoretical physics are used synonymously to refer to the...]
. His many contributions to physics include the
specialSpecial relativity is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies"...
and
generalGeneral relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a...
theories of relativity, the founding of
relativistic cosmologyCosmology is the study of the Universe in its totality, and by extension, humanity's place in it...
, the first
post-Newtonian expansionPost-Newtonian expansions in general relativity are used for finding an approximate solution of the Einstein equations for the metric tensor. The post-Newtonian approximations are expansions in a small parameter, which is the ratio of the velocity of matter, forming the gravitational field, to the...
, explaining the
perihelion advance of MercuryAt its introduction in 1915, the general theory of relativity did not have a solid empirical foundation. It was known that it correctly accounted for the "anomalous" precession of the perihelion of Mercury and on philosophical grounds it was considered satisfying that it was able to unify Newton's...
, prediction of the
deflection of light by gravityAt its introduction in 1915, the general theory of relativity did not have a solid empirical foundation. It was known that it correctly accounted for the "anomalous" precession of the perihelion of Mercury and on philosophical grounds it was considered satisfying that it was able to unify Newton's...
and gravitational lensing, the first
fluctuation dissipation theoremIn statistical physics, the fluctuation dissipation theorem is a powerful tool for predicting the non-equilibrium behavior of a system — such as the irreversible dissipation of energy into heat — from its reversible fluctuations in thermal equilibrium...
which explained the
Brownian movement of moleculesBrownian motion is the seemingly random movement of particles suspended in a fluid or the mathematical model used to describe such random movements, often called a particle theory....
, the
photon theoryIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
and wave-particle duality, the
quantum theory of atomic motion in solidsThe Einstein solid is a model of a solid based on three assumptions:* Each atom in the lattice is a 3D quantum harmonic oscillator* Each atom is attached to a preferred position in space by a spring...
, the
zero-point energyIn physics, the zero-point energy is the lowest possible energy that a quantum mechanical physical system may have and is the energy of the ground state. The quantum mechanical system that encapsulates this energy is the zero-point field. The concept was first proposed by Albert Einstein and Otto...
concept, the semiclassical version of the
Schrödinger equationIn physics, specifically quantum mechanics, the Schrödinger equation is an equation that describes how the quantum state of a physical system changes in time...
, and the quantum theory of a monatomic gas which predicted Bose-Einstein condensation.
Einstein is best known for his theories of special relativity and general relativity. He received the 1921
Nobel Prize in PhysicsThe Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in chemistry, Nobel Prize in literature, Nobel Peace Prize, and...
“for his services to Theoretical Physics, and especially for his discovery of the law of the
photoelectric effectThe photoelectric effect is a phenomenon in which electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as "photoelectrons"...
”.
Einstein published
more than 300 scientific and over 150 non-scientific works. He is often regarded as the father of
modern physicsThe term modern physics refers to the post-Newtonian conception of physics. The term implies that classical descriptions of phenomena are lacking, and that an accurate, "modern", description of reality requires theories to incorporate elements of quantum mechanics or Einsteinian relativity, or both...
.
Early life and education
Albert Einstein was born in
UlmUlm is a city in the German Bundesland of Baden-Württemberg, situated on the River Danube. The city, whose population is estimated at 120,000 , forms an urban district of its own and is the administrative seat of the Alb-Donau district. Ulm, founded around 850, is rich in history and traditions...
, in the
Kingdom of WürttembergThe Kingdom of Württemberg was a state that existed from 1806 to 1918, located in present-day Baden-Württemberg, Germany. It was a continuation of the Duchy of Württemberg, which came into existence in 1495...
in the
German EmpireThe German Empire is the name commonly used in English to describe Germany from the unification of Germany and proclamation of Wilhelm I as German Emperor on 18 January 1871 to 1918, when it became a German republic after defeat in World War I and the abdication of Wilhelm II .The term Second Reich...
on March 14, 1879. His father was
Hermann EinsteinHermann Einstein was the father of Albert Einstein.- Early life :Hermann Einstein was born in Buchau, Württemberg to his parents Abraham Einstein and Helene Moos , who had married in Buchau in April 1839. The family were German Jews...
, a salesman and engineer. His mother was
Pauline Einstein (née Koch)Pauline Einstein is the mother of the physicist Albert Einstein. She was born in Cannstatt, Württemberg. She was Jewish and had an older sister, Fanny, and two older brothers, Jacob and Caesar. Her parents were Julius Doerzbacher, who had accepted the family name Koch in 1842 and Jette...
. In 1880, the family moved to
MunichMunich is the capital city of Bavaria, Germany. It is located on the River Isar north of the Bavarian Alps. Munich is the third largest city in Germany, after Berlin and Hamburg...
, where his father and his uncle founded
Elektrotechnische Fabrik J. Einstein & Cie, a company that manufactured electrical equipment based on
direct currentDirect current is the undirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also be through...
.
The Einsteins were non-observant Jews. Their son attended a
Catholic elementary schoolCatholic schools are education ministries of the Catholic Church. Currently, the Church operates the world's largest non-governmental school system...
from the age of five until ten. Although Einstein had early speech difficulties, he was a top student in elementary school. As he grew, Einstein built models and mechanical devices for fun and began to show a talent for mathematics. In 1889 Max Talmud (later changed to Max Talmey) introduced the ten-year old Einstein to key texts in science, mathematics and philosophy, including
Kant’sImmanuel Kant was an 18th-century German philosopher from the Prussian city of Königsberg...
Critique of Pure ReasonThe Critique of Pure Reason by Immanuel Kant, first published in 1781, second edition 1787, is one of the most influential works in the history of philosophy...
and
Euclid’sEuclid , fl. 300 BC, also known as Euclid of Alexandria, was a Greek mathematician and is often referred to as the "Father of Geometry." He was active in Hellenistic Alexandria during the reign of Ptolemy I...
Elements (which Einstein called the "holy little geometry book"). Talmud was a poor Jewish medical student from Poland. The Jewish community arranged for Talmud to take meals with the Einsteins each week on Thursdays for six years. During this time Talmud wholeheartedly guided Einstein through many secular educational interests.
In 1894, his father’s company failed: Direct current (DC) lost the
War of CurrentsIn the "War of Currents" era in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current for electric power distribution over alternating current advocated by Westinghouse and Nikola Tesla.- Introduction :During the initial years of...
to
alternating currentIn alternating current the movement of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again...
(AC). In search of business, the Einstein family moved to
ItalyItaly , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia. Italy shares its northern, Alpine boundary with France, Switzerland, Austria and Slovenia...
, first to
MilanMilan in Italy, is the capital of the region of Lombardia and of the province of Milan. The city proper has a population of about 1.3 million, while the urban area is the fifth largest in the E.U. with an estimated population of 4.3 million...
and then, a few months later, to
PaviaPavia , the ancient Ticinum, is a town and comune of south-western Lombardy, northern Italy, 35 km south of Milan on the lower Ticino river near its confluence with the Po. It has a population of c. 71,000...
. When the family moved to Pavia, Einstein stayed in Munich to finish his studies at the
Luitpold GymnasiumThe Luitpold-Gymnasium is a secondary school in Munich, Germany. It was established by Prince Luitpold of Bavaria in 1891 as "Luitpold-Kreisrealschule" to serve the eastern part of the city and its suburbs...
. His father intended for him to pursue
electrical engineeringElectrical engineering, sometimes referred to as electrical and electronic engineering, is a field of engineering that deals with the study and application of electricity, electronics and electromagnetism. The field first became an identifiable occupation in the late nineteenth century after...
, but Einstein clashed with authorities and resented the school’s regimen and teaching method. He later wrote that the spirit of learning and creative thought were lost in strict
rote learningRote learning is a learning technique which avoids understanding of a subject and instead focuses on memorization. The major practice involved in rote learning is learning by repetition. The idea is that one will be able to quickly recall the meaning of the material the more one repeats it.Rote...
. In the spring of 1895, he withdrew to join his family in Pavia, convincing the school to let him go by using a doctor’s note. During this time, Einstein wrote his first scientific work, "The Investigation of the State of
AetherAlchemy, natural philosophy, and early modern physics proposed the existence of a medium of the æther , a space-filling substance or field, thought to be necessary as a transmission medium...
in
Magnetic FieldsMagnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges...
".
Einstein applied directly to the
Eidgenössische Polytechnische Schule (later Eidgenössische Technische Hochschule (ETH))Eth is a letter used in Old English, Icelandic, Faroese , and Elfdalian. It was also used in Scandinavia during the Middle Ages, but was subsequently replaced with dh and later d. The capital eth resembles a D with a line partially through the vertical stroke...
in
ZürichZürich or Zurich is the largest city in Switzerland and the capital of the canton of Zürich. The city is Switzerland's main commercial and cultural centre and sometimes called the Cultural Capital of Switzerland, the political capital of Switzerland being Berne...
,
SwitzerlandSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
. Lacking the requisite
MaturaMatura is the word commonly used in Albania, Austria, Bosnia and Herzegovina, Bulgaria, Croatia, Czech Republic, Italy, Liechtenstein, the Republic of Macedonia, Montenegro, Poland, Serbia, Slovakia, Slovenia, Switzerland and Ukraine for the final exams young adults take at the end of...
certificate, he took an entrance examination, which he failed, although he got exceptional marks in mathematics and physics.
The Einsteins sent Albert to
AarauAarau is the capital of the northern Swiss canton of Aargau. The city is also the capital of the district of Aarau. It is German-speaking and predominantly Protestant. Aarau is situated on the Swiss plateau, in the valley of the Aar, on the river's right bank, and at the southern foot of the Jura...
, in northern Switzerland to finish secondary school. While lodging with the family of Professor Jost Winteler, he fell in love with the family’s daughter, Marie. (His sister Maja later married the Winteler son, Paul.) In Aarau, Einstein studied
Maxwell’sJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
electromagnetic theory. At age 17, he graduated, and, with his father’s approval, renounced his citizenship in the German Kingdom of Württemberg to avoid
military serviceGermany has conscription for male citizens. The Basic Law for the Federal Republic of Germany and several special laws Germany has conscription (Wehrpflicht) for male citizens. The Basic Law for the Federal Republic of Germany and several special laws Germany has conscription (Wehrpflicht) for...
, and enrolled in 1896 in the mathematics and physics program at the Polytechnic in Zurich. Marie Winteler moved to
Olsberg, SwitzerlandOlsberg is a municipality in the district of Rheinfelden in the canton of Aargau in Switzerland....
for a teaching post.
In the same year, Einstein’s future wife,
Mileva MarićMileva Marić was one of the first women to study mathematics and physics in Europe...
, also entered the Polytechnic to study mathematics and physics, the only woman in the academic cohort. Over the next few years, Einstein and Marić’s friendship developed into romance. In a letter to her, Einstein called Marić "a creature who is my equal and who is as strong and independent as I am." Einstein graduated in 1900 from the Polytechnic with a diploma in mathematics and physics; Although historians have debated whether Marić influenced Einstein’s work, the majority of academic historians of science agree that she did not.
Marriages and children
In early 1902, Einstein and
Mileva MarićMileva Marić was one of the first women to study mathematics and physics in Europe...
had a daughter they called
LieserlLieserl was the first child of Mileva Marić and Albert Einstein.- Life :...
in their correspondence, who was born in
Novi SadNovi Sad is the capital of the northern Serbian province of Vojvodina, and the administrative centre of the South Bačka District. The city lies in the southern part of Central Europe's Pannonian Plain, on both banks of the Danube river.Novi Sad is Serbia's second largest city, after Belgrade...
where the parents of Mileva lived. Her full name is not known, and her fate is uncertain after 1903. Einstein and Marić married in January 1903, and in May 1904 the couple’s first son,
Hans Albert EinsteinHans Albert Einstein was a professor of hydraulic engineering at the University of California, Berkeley...
, was born in Bern,
SwitzerlandSwitzerland , officially the Swiss Confederation , is a federal republic consisting of 26 states named cantons, with Bern as the seat of the federal authorities...
. Their second son,
EduardEduard Einstein was born in Zurich, the second son of physicist Albert Einstein and his first wife Mileva Marić. Einstein and his family moved to Berlin in 1914, but shortly thereafter Mileva returned to Zurich, taking Eduard and his brother.Eduard was a good student and had musical talent...
, was born in
ZurichZürich or Zurich is the largest city in Switzerland and the capital of the canton of Zürich. The city is Switzerland's main commercial and cultural centre and sometimes called the Cultural Capital of Switzerland, the political capital of Switzerland being Berne...
in July 1910. In 1914, Einstein moved to Berlin, while his wife remained in Zurich with their sons. Marić and Einstein divorced on 14 February 1919, having lived apart for five years. Einstein married
Elsa LöwenthalElsa Einstein was a German cousin and the second wife of Albert Einstein. Elsa had the surname of Einstein at birth, lost it when she took the name of her first husband Max Löwenthal, and regained it in 1919 when she married her cousin Albert.-Early life:Elsa, the daughter of Rudolf Einstein and...
(née Einstein) on June 2, 1919 after having had a relationship with her since 1912. She was his first cousin maternally and his second cousin paternally. In 1933, they emigrated permanently to the United States. In 1935, Elsa Einstein was diagnosed with heart and kidney problems and died in December, 1936.
Patent office
After graduating, Einstein spent almost two frustrating years searching for a teaching post, but a former classmate’s father helped him secure a job in Bern, at the
Federal Office for Intellectual PropertyThe Swiss Federal Institute of Intellectual Property is the federal agency in charge of intellectual property matters in Switzerland. Its seat is in Bern...
, the patent office, as an assistant examiner. He evaluated
patent applicationA patent application is a request pending at a patent office for the grant of a patent for the invention described and claimed by that application. An application consists of a description of the invention , together with official forms and correspondence relating to the application...
s for electromagnetic devices. In 1903, Einstein’s position at the Swiss Patent Office became permanent, although he was passed over for promotion until he "fully mastered machine technology".
Much of his work at the patent office related to questions about transmission of electric signals and electrical-mechanical synchronization of time, two technical problems that show up conspicuously in the
thought experimentA thought experiment, sometimes called a gedankenexperiment in German, is a proposal for an experiment that would test or illuminate a hypothesis or theory....
s that eventually led Einstein to his radical conclusions about the nature of light and the fundamental connection between space and time.
With friends he met in Bern, Einstein formed a weekly discussion club on science and philosophy, which he jokingly named "The
Olympia AcademyThe Olympia Academy was a group of friends in Bern, Switzerland, who met – usually at Albert Einstein's flat – in order to discuss philosophy and physics....
." Their readings included
Henri PoincaréJules Henri Poincaré was a French mathematician and theoretical physicist, and a philosopher of science...
,
Ernst MachErnst Mach was an Austrian physicist and philosopher, remembered for his contributions to physics such as the Mach number and the study of shock waves...
, and
David HumeDavid Hume was a Scottish philosopher, economist, historian and a key figure in the history of Western philosophy and the Scottish Enlightenment...
, who influenced Einstein’s scientific and philosophical outlook. The next year, Einstein published a paper in the prestigious
Annalen der PhysikAnnalen der Physik is one of the best-known and oldest physics journals worldwide.The journal publishes original papers in the areas of experimental, theoretical, applied and mathematical physics and related areas...
on the
capillary forcesCapillary action, capillarity, capillary motion, or wicking refers to two phenomena:1 The movement of liquids in thin tubes.
2 The flow of liquids through porous media, such as the flow of water through soil....
of a straw.
Scientific career
Throughout his life, Einstein published hundreds of books and articles. Most were about physics, but a few expressed leftist political opinions about
pacifismPacifism is the opposition to war or violence as a means of settling disputes or gaining advantage. Pacifism covers a spectrum of views ranging from the belief that international disputes can and should be peacefully resolved; to calls for the abolition of the institutions of the military and war;...
,
socialismSocialism refers to various theories of economic organization advocating public or direct worker ownership and administration of the means of production and allocation of resources, and a society characterized by equal access to resources for all individuals with a method of compensation based on...
, and
zionismZionism is the international political movement that originally supported the reestablishment of a homeland for the Jewish People in Palestine. The area was the Jewish Biblical homeland, called the Land of Israel...
. In addition to the work he did by himself he also collaborated with other scientists on additional projects including the Bose-Einstein statistics, the Einstein refrigerator and others.
Physics in 1900
Einstein’s early papers all come from attempts to demonstrate that atoms exist and have a finite nonzero size. At the time of his first paper in 1902, it was not yet completely accepted by physicists that atoms were real, even though chemists had good evidence ever since
Antoine LavoisierAntoine-Laurent de Lavoisier ; ), the father of modern chemistry, was a French noble prominent in the histories of chemistry and biology...
’s work a century earlier. The reason physicists were skeptical was because no 19th century theory could fully explain the properties of matter from the properties of atoms.
Ludwig BoltzmannLudwig Eduard Boltzmann was an Austrian physicist famous for his founding contributions in the fields of statistical mechanics and statistical thermodynamics...
was a leading 19th century atomist physicist, who had struggled for years to gain acceptance for atoms. Boltzmann had given an interpretation of the laws of thermodynamics, suggesting that the law of entropy increase is statistical. In Boltzmann’s way of thinking, the entropy is the logarithm of the number of ways a system could be configured inside. The reason the entropy goes up is only because it is more likely for a system to go from a special state with only a few possible internal configurations to a more generic state with many. While Boltzmann’s statistical interpretation of entropy is universally accepted today, and Einstein believed it, at the turn of the 20th century it was a minority position.
The statistical idea was most successful in explaining the properties of gases.
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
, another leading atomist, had found the distribution of velocities of atoms in a gas, and derived the surprising result that the
viscosityViscosity is a measure of the resistance of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness." Thus, water is "thin," having a lower viscosity, while honey is "thick," having a higher viscosity...
of a gas should be independent of density. Intuitively, the friction in a gas would seem to go to zero as the density goes to zero, but this is not so, because the
mean free pathIn physics the mean free path of a particle is the average distance covered by a particle between successive impacts.. Alternatively, it is the distance at which the intensity of particles drops by 1/e.-Derivation:...
of atoms becomes large at low densities. A subsequent experiment by Maxwell and his wife confirmed this surprising prediction. Other experiments on gases and vacuum, using a rotating slitted drum, showed that atoms in a gas had velocities distributed according to Maxwell’s distribution law.
In addition to these successes, there were also inconsistencies. Maxwell noted that at cold temperatures, atomic theory predicted specific heats that are too large. In classical
statistical mechanicsStatistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force...
, every spring-like motion has thermal energy
kBT on average at temperature
T, so that the specific heat of every spring is Boltzmann’s constant
kB. A monatomic solid with
N atoms can be thought of as
N little balls representing
N atoms attached to each other in a box grid with 3
N springs, so the specific heat of every solid is 3
NkB, a result which became known as the Dulong-Petit law. This law is true at room temperature, but not for colder temperatures. At temperatures near zero, the specific heat goes to zero.
Similarly, a gas made up of a molecule with two atoms can be thought of as two balls on a spring. This spring has energy
kBT at high temperatures, and should contribute an extra
kB to the specific heat. It does at temperatures of about 1000 degrees, but at lower temperature, this contribution disappears. At zero temperature, all other contributions to the specific heat from rotations and vibrations also disappear. This behavior was inconsistent with classical physics.
The most glaring inconsistency was in the theory of light waves. Continuous waves in a box can be thought of as infinitely many spring-like motions, one for each possible
standing waveA standing wave, also known as a stationary wave, is a wave that remains in a constant position. This phenomenon can occur because the medium is moving in the opposite direction to the wave, or it can arise in a stationary medium as a result of interference between two waves traveling in opposite...
. Each standing wave has a specific heat of
kB, so the total specific heat of a continuous wave like light should be infinite in classical mechanics. This is obviously wrong, because it would mean that all energy in the universe would be instantly sucked up into light waves, and everything would slow down and stop.
These inconsistencies led some people to say that atoms were not physical, but mathematical. Notable among the skeptics was
Ernst MachErnst Mach was an Austrian physicist and philosopher, remembered for his contributions to physics such as the Mach number and the study of shock waves...
, whose logical positivist philosophy led him to demand that if atoms are real, it should be possible to see them directly. Mach believed that atoms were a useful fiction, that in reality they could be assumed to be infinitesimally small, that Avogadro’s number was infinite, or so large that it might as well be infinite, and
kB was infinitesimally small. Certain experiments could then be explained by atomic theory, but other experiments could not, and this is the way it will always be.
Einstein opposed this position. Throughout his career, he was a realist. He believed that a single consistent theory should explain all observation, and that this theory would be a description what was really going on, underneath it all. So he set out to show that the atomic point of view was correct. This led him first to thermodynamics, then to statistical physics, and to the theory of specific heats of solids.
In 1905, while he was working in the patent office, the leading German language physics journal
Annalen der PhysikAnnalen der Physik is one of the best-known and oldest physics journals worldwide.The journal publishes original papers in the areas of experimental, theoretical, applied and mathematical physics and related areas...
published four of Einstein’s papers. The four papers eventually were recognized as revolutionary, and 1905 became known as Einstein’s "
Miracle YearAnnus mirabilis is a Latin phrase meaning "wonderful year" or "year of wonders" . It was used originally to refer to the year 1666, but is today also used to refer to different years with events of major importance such as 1905 when Albert Einstein published his breakthrough four articles on Physics...
", and the papers, as the
Annus Mirabilis PapersThe Annus Mirabilis papers are the papers of Albert Einstein published in the Annalen der Physik scientific journal in 1905. These four articles contributed substantially to the foundation of modern physics and changed views on space, time, and matter...
.
Thermodynamic fluctuations and statistical physics
Einstein’s earliest papers were concerned with
thermodynamicsIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
. He wrote a paper establishing a thermodynamic identity in 1902, and a few other papers which attempted to interpret phenomena from a statistical atomic point of view.
His research in 1903 and 1904 was mainly concerned with the effect of finite atomic size on diffusion phenomena. As in Maxwell’s work, the finite nonzero size of atoms leads to effects which can be observed. This research, and the thermodynamic identity, were well within the mainstream of physics in his time. They would eventually form the content of his PhD thesis.
His first major result in this field was the theory of thermodynamic fluctuations. When in equilibrium, a system has a maximum entropy and according to the statistical interpretation, it can fluctuate a little bit. Einstein pointed out that the statistical fluctuations of a macroscopic object, like a mirror suspended on spring, would be completely determined by the second derivative of the entropy with respect to the position of the mirror. This makes a connection between microscopic and macroscopic objects.
Searching for ways to test this relation, his great breakthrough came in 1905. The theory of fluctuations, he realized, would have a visible effect for an object which could move around freely. Such an object would have a velocity which is random, and would move around randomly, just like an individual atom. The average kinetic energy of the object would be , and the time decay of the fluctuations would be entirely determined by the law of friction.
The law of friction for a small ball in a viscous fluid like water was discovered by George Stokes. He showed that for small velocities, the friction force would be proportional to the velocity, and to the radius of the particle (see Stokes’ law). This relation could be used to calculate how far a small ball in water would travel due to its random thermal motion, and Einstein noted that such a ball, of size about a
micronMicron can refer to:*Micron, an obsolete name for micrometre, a unit of length in the metric system: one millionth of a metre, formerly abbreviated with the Greek letter μ...
, would travel about a few microns per second. This motion could be easily observed with a microscope.
Such a motion had already been observed with a microscope by a Botanist named Brown, and had been called
Brownian motionBrownian motion is the seemingly random movement of particles suspended in a fluid or the mathematical model used to describe such random movements, often called a particle theory....
. Einstein was able to identify this motion with the motion predicted by his theory. Since the fluctuations which give rise to Brownian motion are just the same as the fluctuations of the velocities of atoms, measuring the precise amount of Brownian motion using Einstein’s theory would show that Boltzmann’s constant is nonzero. It would measure Avogadro’s number.
These experiments were carried out a few years later, and gave a rough estimate of Avogadro’s number consistent with the more accurate estimates due to
Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
’s theory of blackbody light, and
Robert MillikanRobert A. Millikan was an American experimental physicist, and Nobel laureate in physics for his measurement of the charge on the electron and for his work on the photoelectric effect. He served as president of Caltech from 1921 to 1945.-Education:Millikan went to high school in Maquoketa, Iowa...
’s measurement of the charge of the electron. Unlike the other methods, Einstein’s required very few theoretical assumptions or new physics, since it was directly measuring atomic motion on visible grains.
Einstein’s theory of Brownian motion was the first paper in the field of
statistical physicsStatistical physics is the area of physics that uses methods of probability theory and statistics, and particularly the mathematical tools for dealing with large populations, in solving physical problems. It can describe a wide variety of fields with an inherently stochastic nature...
. It established that thermodynamic fluctuations were related to dissipation. This was shown by Einstein to be true for time-independent fluctuations, but in the Brownian motion paper he showed that dynamical relaxation rates calculated from classical mechanics could be used as statistical relaxation rates to derive dynamical diffusion laws. These relations are known as
Einstein relationsIn physics the Einstein relation is a previously unexpected connection revealed independently by Albert Einstein in 1905 and by Marian Smoluchowski in their papers on Brownian motion:linking D, the diffusion constant, and μp, the mobility of the particles; where is...
.
The theory of Brownian motion was the least revolutionary of Einstein’s
Annus mirabilisAnnus mirabilis is a Latin phrase meaning "wonderful year" or "year of wonders" . It was used originally to refer to the year 1666, but is today also used to refer to different years with events of major importance such as 1905 when Albert Einstein published his breakthrough four articles on Physics...
papers, but it had an important role in securing the acceptance of the atomic theory by physicists.
Thought experiments and a-priori physical principles
Einstein’s thinking underwent a transformation in 1905. He had come to understand that quantum properties of light mean that Maxwell’s equations were only an approximation. He knew that new laws would have to replace these, but he did not know how to go about finding those laws. He felt that guessing formal relations would not go anywhere.
So he decided to focus on a-priori principles instead, which are statements about physical laws which can be understood to hold in a very broad sense even in domains where they have not yet been shown to apply. A well accepted example of an a-priori principle is
rotational invarianceIn mathematics, a function defined on an inner product space is said to have rotational invariance if its value does not change when arbitrary rotations are applied to its argument...
. If a new force is discovered in physics, it is assumed to be rotationally invariant almost automatically, without thought. Einstein sought new principles of this sort, to guide the production of physical ideas. Once enough principles are found, then the new physics will be the simplest theory consistent with the principles and with previously known laws.
The first general a-priori principle he found was the
principle of relativityIn physics, the principle of relativity is the requirement that the equations, describing the laws of physics, have the same form in all admissible frames of reference....
, that uniform motion is indistinguishable from rest. This was understood by Hermann Minkowski to be a generalization of rotational invariance from space to space-time. Other principles postulated by Einstein and later vindicated, are the principle of equivalence and the principle of
adiabatic invarianceAn adiabatic invariant is a property of a physical system which stays constant when changes are made slowly.In thermodynamics, an adiabatic process is a change that occurs without heat flow and slowly compared to the time to reach equilibrium. In an adiabatic process, the system is in equilibrium...
of the quantum number. Another of Einstein’s general principles, Mach’s principle is fiercely debated, and whether it holds in our world or not is still not definitively established.
The use of a-priori principles is a distinctive unique signature of Einstein’s early work, which has become a standard tool in modern theoretical physics.
Special relativity
His 1905 paper on the electrodynamics of moving bodies introduced the radical theory of
special relativitySpecial relativity is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies"...
, which showed that the observed independence of the
speed of lightIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
on the observer’s state of motion required fundamental changes to the
notion of simultaneityThe relativity of simultaneity is the concept that simultaneity is not absolute, but dependent on the observer . That is, according to the special theory of relativity, it is impossible to say in an absolute sense whether two events occur at the same time if those events are separated in space...
. Consequences of this include the
time-space frameIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions...
of a moving body
slowing downTime dilation is a phenomenon described by the theory of relativity. It can be illustrated by supposing that two observers are in motion relative to each other, and/or differently situated with regard to nearby gravitational masses. They each carry a clock of identically similar construction and...
and
contractingLength contraction, according to Hendrik Lorentz, is the physical phenomenon of a decrease in length detected by an observer in objects that travel at any non-zero velocity relative to that observer...
(in the direction of motion) relative to the frame of the observer. This paper also argued that the idea of a
luminiferous aetherIn the late 19th century, "luminiferous aether" , meaning light-bearing aether, was the term used to describe a medium for the propagation of light. The word aether stems via Latin from the Greek αιθήρ, from a root meaning to kindle, burn, or shine...
—one of the leading theoretical entities in physics at the time—was superfluous.
In his paper on
mass-energy equivalenceIn physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. The mass of a body as measured on a scale is always equal to the total energy inside, multiplied by a constant c
2 that changes the units appropriately:where E is energy, m is...
, which had previously considered to be distinct concepts, Einstein deduced from his equations of special relativity what has been called the twentieth century’s best-known equation:
E =
mc2. This equation suggests that tiny amounts of mass could be
convertedIn physics, mass–energy equivalence is the concept that the mass of a body is a measure of its energy content. The mass of a body as measured on a scale is always equal to the total energy inside, multiplied by a constant c
2 that changes the units appropriately:where E is energy, m is...
into huge amounts of energy and presaged the development of
nuclear powerNuclear power is power produced from controlled nuclear reactions. Commercial plants in use to date use nuclear fission reactions....
.
Einstein’s 1905 work on relativity remained controversial for many years, but was accepted by leading physicists, starting with
Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
.
Photons
In a 1905 paper, Einstein postulated that light itself consists of localized particles (
quanta). Einstein’s light quanta were nearly universally rejected by all physicists, including
Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
and
Niels BohrNiels Henrik David Bohr was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
. This idea only became universally accepted in 1919, with
Robert MillikanRobert A. Millikan was an American experimental physicist, and Nobel laureate in physics for his measurement of the charge on the electron and for his work on the photoelectric effect. He served as president of Caltech from 1921 to 1945.-Education:Millikan went to high school in Maquoketa, Iowa...
’s detailed experiments on the photoelectric effect, and with the measurement of
Compton scatteringIn physics, Compton scattering or the Compton effect is the decrease in energy of an X-ray or gamma ray photon, when it interacts with matter. Because of the change in photon energy, it is an inelastic scattering process. Inverse Compton scattering also exists, where the photon gains energy upon...
.
Einstein’s paper on the light particles was almost entirely motivated by thermodynamic considerations. He was not at all motivated by the detailed experiments on the photoelectric effect, which did not confirm his theory until fifteen years later.
Einstein considers the entropy of light at temperature
T, and decomposes it into a low-frequency part and a high-frequency part. The high-frequency part, where the light is described by Wien’s law, has an entropy which looks exactly the same as the entropy of a gas of classical particles.
Since the entropy is the logarithm of the number of possible states, Einstein concludes that the number of states of short wavelength light waves in a box with volume
V is equal to the number of states of a group of localizable particles in the same box. Since (unlike others) he was comfortable with the statistical interpretation, he confidently postulates that the light itself is made up of localized particles, as this is the only reasonable interpretation of the entropy.
This leads him to conclude that each wave of frequency
f is associated with a collection of
photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s with energy
hf each, where
h is Planck’s constant. He does not say much more, because he is not sure how the particles are related to the wave. But he does suggest that this idea would explain certain experimental results, notably the
photoelectric effectThe photoelectric effect is a phenomenon in which electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as "photoelectrons"...
.
Quantized atomic vibrations
Einstein continued his work on quantum mechanics in 1906, by explaining the specific heat anomaly in solids. This was the first application of quantum theory to a mechanical system.
Since Planck’s distribution for light oscillators had no problem with infinite specific heats, the same idea could be applied to solids to fix the specific heat problem there. Einstein showed in a
simple modelThe Einstein solid is a model of a solid based on three assumptions:* Each atom in the lattice is a 3D quantum harmonic oscillator* Each atom is attached to a preferred position in space by a spring...
that the hypothesis that solid motion is quantized explains why the specific heat of a solid goes to zero at zero temperature.
Einstein’s model treats each atom as connected to a single spring. Instead of connecting all the atoms to each other, which leads to standing waves with all sorts of different frequencies, Einstein imagined that each atom was attached to a fixed point in space by a spring. This is not physically correct, but it still predicts that the specific heat is 3
NkB, since the number of independent oscillations stays the same.
Einstein then assumes that the motion in this model are quantized, according to the Planck law, so that each independent spring motion has energy which is an integer multiple of hf, where f is the frequency of oscillation. With this assumption, he applied Boltzmann’s statistical method to calculate the average energy of the spring. The result was the same as the one that Planck had derived for light: for temperatures where
kBT is much smaller than
hf, the motion is frozen, and the specific heat goes to zero.
So Einstein concluded that quantum mechanics would solve the main problem of classical physics, the specific heat anomaly. The particles of sound implied by this formulation are now called
phononIn physics, a phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the atomic lattice of a solid. The study of phonons is an important part of solid state physics, because phonons play a major role in many of the physical properties of solids, including a material's...
s. Because all of Einstein’s springs have the same stiffness, they all freeze out at the same temperature, and this leads to a prediction that the specific heat should go to zero exponentially fast when the temperature is low. The solution to this problem is to solve for the independent normal modes individually, and to quantize those. Then each normal mode has a different frequency, and long wavelength vibration modes freeze out at colder temperatures than short wavelength ones. This was done by
DebyeThe debye is a CGS unit of electric dipole moment
[Electric dipole moment is defined as charge times displacement:] Historically the debye was defined as the dipole moment resulting from two charges of opposite sign but an equal magnitude of 10
-10 statcoulomb
, and after this modification, Einstein’s quantization method reproduced quantitatively the behavior of the specific heats of solids at low temperatures.
This work was the foundation of condensed matter physicsCondensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter. In particular, it is concerned with the "condensed" phases that appear whenever the number of constituents in a system is extremely large and the interactions between the...
.
Adiabatic principle and action-angle variables
Throughout the 1910s, quantum mechanics expanded in scope to cover many different systems. After Ernest RutherfordErnest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS was a New Zealand chemist and physicist who became known as the father of nuclear physics....
discovered the nucleus and proposed that electrons orbit like planets, Niels BohrNiels Henrik David Bohr was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
was able to show that the same quantum mechanical postulates introduced by Planck and developed by Einstein would explain the discrete motion of electrons in atoms, and the periodic table of the elements.
Einstein contributed to these developments by linking them with the 1898 arguments Wilhelm WienWilhelm Carl Werner Otto Fritz Franz Wien was a German physicist who, in 1893, used theories about heat and electromagnetism to deduce Wien's displacement law, which calculates the emission of a blackbody at any temperature from the emission at any one reference temperature.He also formulated an...
had made. Wien had shown that the hypothesis of adiabatic invarianceAn adiabatic invariant is a property of a physical system which stays constant when changes are made slowly.In thermodynamics, an adiabatic process is a change that occurs without heat flow and slowly compared to the time to reach equilibrium. In an adiabatic process, the system is in equilibrium...
of a thermal equilibrium state allows all the blackbody curves at different temperature to be derived from one another by a simple shifting process. Einstein noted in 1911 that the same adiabatic principle shows that the quantity which is quantized in any mechanical motion must be an adiabatic invariant. Arnold SommerfeldArnold Johannes Wilhelm Sommerfeld was a German theoretical physicist who pioneered developments in atomic and quantum physics, and also educated and groomed a large number of students for the new era of theoretical physics...
identified this adiabatic invariant as the action variable of classical mechanics. The law that the action variable is quantized was the basic principle of the quantum theory as it was known between 1900 and 1925.
Wave-particle duality
Although the patent office promoted Einstein to Technical Examiner Second Class in 1906, he had not given up on academia. In 1908, he became a privatdozentPrivate docent is a title conferred in some European university systems, especially in German-speaking countries, for someone who pursues an academic career and holds all formal qualifications to become a tenured university professor.-Becoming:Privatedocentship is conferred to academics who have...
at the University of Bern.
In "über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung" ("The Development of Our Views on the Composition and Essence of Radiation"), on the quantizationIn physics, quantization is the process of explaining a classical understanding of physical phenomena in terms of a newer understanding known as "quantum mechanics". It is a procedure for constructing a quantum field theory starting from a classical field theory. This is a generalization of the...
of light, and in an earlier 1909 paper, Einstein showed that Max PlanckMax Planck was a German physicist. He is considered to be the founder of the quantum theory, and thus one of the most important physicists of the twentieth century. Planck was awarded the Nobel Prize in Physics in 1918.-Biography:Planck came from a traditional, intellectual family...
’s energyIn physics, energy is a scalar physical quantity that describes the amount of work that can be performed by a force, an attribute of objects and systems that is subject to a conservation law...
quanta must have well-defined momentaIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
and act in some respects as independent, point-like particlesA point particle is an idealized object heavily used in physics. Its defining feature is that it lacks spatial extension: being zero-dimensional, it does not take up space...
. This paper introduced the photonIn physics, a photon is an elementary particle, the quantum of the electromagnetic field and the basic "unit" of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
concept (although the name photon was introduced later by Gilbert N. LewisGilbert Newton Lewis was an American physical chemist known for the discovery of the covalent bond , his purification of heavy water, his reformulation of chemical thermodynamics in a mathematically rigorous manner accessible to ordinary chemists, his theory of Lewis acids and...
in 1926) and inspired the notion of wave-particle duality in quantum mechanicsQuantum mechanics is a set of principles describing the physical reality at the atomic level of matter and the subatomic . These descriptions include the simultaneous wave-like and particle-like behavior of both matter and radiation...
.
Theory of Critical Opalescence
Einstein returned to the problem of thermodynamic fluctuations, giving a treatment of the density variations in a fluid at its critical point. Ordinarily the density fluctuations are controlled by the second derivative of the free energy with respect to the density. At the critical point, this derivative is zero, leading to large fluctuations. The effect of density fluctuations is that light of all wavelengths is scattered, making the fluid look milky white. Einstein relates this to Raleigh scattering, which is what happens when the fluctuation size is much smaller than the wavelength, and which explains why the sky is blue.
Zero-point energy
Einstein’s physical intuition led him to note that Planck’s oscillator energies had an incorrect zero point. He modified Planck’s hypothesis by stating that the lowest energy state of an oscillator is equal to hf, to half the energy spacing between levels. This argument, which was made in 1913 in collaboration with Otto SternOtto Stern was a German physicist and Nobel laureate in physics.-Biography:Stern was born in Sohrau, now Żory in the German Empire's Kingdom of Prussia and studied at Breslau, now Wrocław in Lower Silesia....
, was based on the thermodynamics of a diatomic molecule which can split apart into two free atoms.
Principle of equivalence
In 1907, while still working at the patent office, Einstein had what he would call his "happiest thought". He realized that the principle of relativity could be extended to gravitational fields.
He thought about the case of a uniformly accelerated box not in a gravitational field, and noted that it would be indistinguishable from a box sitting still in an unchanging gravitational field. He used special relativity to see that the rate of clocks at the top of a box accelerating upward would be faster than the rate of clocks at the bottom. He concludes that the rates of clocks depend on their position in a gravitational field, and that the difference in rate is proportional to the gravitational potential to first approximation.
Although this approximation is crude, it allowed him to calculate the deflection of light by gravity, and show that it is nonzero. This gave him confidence that the scalar theory of gravity proposed by Gunnar NordströmGunnar Nordström was a Finnish theoretical physicist who is best remembered for his theory of gravitation, which was an early competitor of general relativity....
was incorrect. But the actual value for the deflection that he calculated was too small by a factor of two, because the approximation he used doesn’t work well for things moving at near the speed of light. When Einstein finished the full theory of general relativity, he would rectify this error, and predict the correct amount of light deflection by the sun.
From Prague, Einstein published a paper about the effects of gravity on light, specifically the gravitational redshiftIn physics, light or other forms of electromagnetic radiation of a certain wavelength originating from a source placed in a region of stronger gravitational field will be found to be of longer wavelength when received by an observer in a region of weaker gravitational field...
and the gravitational deflection of light. The paper challenged astronomers to detect the deflection during a solar eclipseA solar eclipse occurs when the moon passes between the Sun and the Earth so that the Sun is fully or partially covered. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from the Earth. At least two and up to five solar eclipses can occur each year on Earth,...
. German astronomer Erwin Finlay-FreundlichErwin Finlay-Freundlich [Scottish name:"Finlay"] was a German astronomer, a pupil of Felix Klein. He was born in Biebrich, Germany...
publicized Einstein’s challenge to scientists around the world.
Einstein thought about the nature of the gravitational field in the years 1909-1912, studying its properties by means of simple thought experiments. A notable one is the rotating disk. Einstein imagined an observer making experiments on a rotating turntable. He noted that such an observer would find a different value for the mathematical constant pi than the one predicted by Euclidean geometry. The reason is that the radius of a circle would be measured with an uncontracted ruler, but according to special relativity, the circumference would seem to be longer, because the ruler would be contracted.
Since Einstein believed that the laws of physics were local, described by local fields, he concluded from this that spacetime could be locally curved. This led him to study Riemannian geometryRiemannian geometry is the branch of differential geometry that studies Riemannian manifolds, smooth manifolds with a Riemannian metric, i.e. with an inner product on the tangent space at each point which varies smoothly from point to point. This gives in particular local notions of angle, length...
, and to formulate general relativity in this language.
Hole argument and Entwurf theory
While developing general relativity, Einstein became confused about the gauge invariance in the theory. He formulated an argument that led him to conclude that a general relativistic field theory is impossible. He gave up looking for fully generally covariant tensor equations, and searched for equations that would be invariant under general linear transformations only.
The Entwurf theory was the result of these investigations. As it name suggests, it was a sketch of a theory, with the equations of motion supplemented by additional gauge fixing conditions. Simultaneously less elegant and more difficult than general relativity, Einstein abandoned the theory after realizing that the hole argument was mistaken.
General relativity
In 1912, Einstein returned to Switzerland to accept a professorship at his alma mater, the ETH. Once back in Zurich, he immediately visited his old ETH classmate Marcel GrossmannMarcel Grossmann was a mathematician of Jewish ancestry, and a friend and classmate of Albert Einstein...
, now a professor of mathematics, who introduced him to Riemannian geometry and, more generally, to differential geometry. On the recommendation of Italian mathematician Tullio Levi-CivitaTullio Levi-Civita was an Italian mathematician, most famous for his work on absolute differential calculus and its applications to the theory of relativity but who also made significant contributions in other areas. He was a pupil of Gregorio Ricci-Curbastro, the inventor of tensor calculus...
, Einstein began exploring the usefulness of general covarianceIn theoretical physics, general covariance is the invariance of the form of physical laws under arbitrary differentiable coordinate transformations...
(essentially the use of tensorTensors are geometrical entities introduced into mathematics and physics to extend the notion of scalars, vectors, and matrices. Many physical quantities are naturally regarded, not as vectors themselves, but as correspondences between one set of vectors and another...
s) for his gravitational theory. For a while Einstein thought that there were problems with the approach, but he later returned to it and, by late 1915, had published his general theory of relativity in the form in which it is used today. This theory explains gravitation as distortion of the structure of spacetimeIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions...
by matter, affecting the inertiaInertia is the resistance of any physical object, to a change in its state of motion. It is represented numerically by an object's mass. The principle of inertia is one of the fundamental principles of classical physics which are used to describe the motion of matter and how it is affected by...
l motion of other matter.
During World War I, the work of Central PowersThe Central Powers was one of the two sides that participated in World War I, the other being the Entente Powers.-Member states:...
scientists was available only to Central Powers academics, for national security reasons. Some of Einstein’s work did reach the United Kingdom and the United States through the efforts of the Austrian Paul EhrenfestPaul Ehrenfest was an Austrian physicist and mathematician, who obtained Dutch citizenship on March 24, 1922. He made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition and the Ehrenfest theorem...
and physicists in the Netherlands, especially 1902 Nobel Prize-winner Hendrik LorentzHendrik Antoon Lorentz was a Dutch physicist who shared the 1902 Nobel Prize in Physics with Pieter Zeeman for the discovery and theoretical explanation of the Zeeman effect...
and Willem de SitterWillem de Sitter was a Dutch mathematician, physicist and astronomer.Born in Sneek, De Sitter studied mathematics at the University of Groningen and then joined the Groningen astronomical laboratory. He worked at the Cape Observatory in South Africa . Then, in 1908, de Sitter was appointed to the...
of Leiden UniversityLeiden University , located in the city of Leiden, is the oldest university in the Netherlands. The university was founded in 1575 by Prince William of Orange, leader of the Dutch Revolt in the Eighty Years' War. The royal Dutch House of Orange-Nassau and Leiden University still have a close...
. After the war ended, Einstein maintained his relationship with Leiden University, accepting a contract as an Extraordinary Professor; for ten years, from 1920 to 1930, he travelled to Holland regularly to lecture.
In 1917, several astronomers accepted Einstein ’s 1911 challenge from Prague. The Mount Wilson ObservatoryThe Mount Wilson Observatory is an astronomical observatory in Los Angeles County, California. The MWO is located on Mount Wilson, a 5,715 foot peak in the San Gabriel Mountains near Pasadena, northeast of Los Angeles....
in California, U.S., published a solar spectroscopic analysis that showed no gravitational redshift. In 1918, the Lick ObservatoryThe Lick Observatory is an astronomical observatory, owned and operated by the University of California. It is situated on the summit of Mount Hamilton, in the Diablo Range just east of San Jose, California, USA...
, also in California, announced that it too had disproved Einstein’s prediction, although its findings were not published.
However, in May 1919, a team led by the British astronomer Arthur Stanley EddingtonSir Arthur Stanley Eddington, OM, FRS was a British astrophysicist of the early 20th century. The Eddington limit, the natural limit to the luminosity of stars, or the radiation generated by accretion onto a compact object, is named in his honour.He is famous for his work regarding the Theory of...
claimed to have confirmed Einstein’s prediction of gravitational deflection of starlight by the Sun while photographing a solar eclipse with dual expeditions in SobralSobral is a city and municipality in the state of Ceará, Brazil.Sobral is the second largest municipality of Ceará, after Fortaleza. Its economy is based on agriculture, services and some manufacturing industries...
, northern BrazilBrazil , officially the Federative Republic of Brazil , is a country in South America. It is the fifth largest country by geographical area, occupying nearly half of South America, the fifth most populous country, and the fourth most populous democracy in the world. Bounded by the Atlantic Ocean...
, and PríncipePríncipe is the smaller of the two major islands of São Tomé and Príncipe lying off the west coast of Africa. It has an area of 136 km² and a population of around 5,000 people. It rises in the south to 948 metres at Pico de Príncipe, in a thickly forested area forming part of the Obo National Park...
, a west African island. Nobel laureate Max BornMax Born was a German born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...
praised general relativity as the "greatest feat of human thinking about nature"; fellow laureate Paul DiracPaul Adrien Maurice Dirac, OM, FRS was a British theoretical physicist. Dirac made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics...
was quoted saying it was "probably the greatest scientific discovery ever made".
The international media guaranteed Einstein’s global renown. There have been later claims that scrutiny of the specific photographs taken on the Eddington expedition showed the experimental uncertainty to be comparable to the same magnitude as the effect Eddington claimed to have demonstrated, and that a 1962 British expedition concluded that the method was inherently unreliable. The deflection of light during a solar eclipse was confirmed by later, more accurate observations. Some resented the newcomer’s fame, notably among some German physicists, who later started the Deutsche PhysikDeutsche Physik or Aryan Physics was a nationalist movement in the German physics community in the early 1930s against the work of Albert Einstein, labeled "Jewish Physics"...
(German Physics) movement.
Cosmology
In 1917, Einstein applied the General theory of relativity to model the structure of the universe as a whole. He wanted the universe to be eternal and unchanging, but this type of universe is not consistent with relativity. To fix this, Einstein modified the general theory by introducing a new notion, the cosmological constantIn physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...
. With a positive cosmological constant, the universe could be an eternal static sphere
Einstein believed a spherical static universe is philosophically preferred, because it would obey Mach’s principle. He had shown that general relativity incorporates Mach’s principle to a certain extent in frame dragging by gravitomagnetic fieldsGravitomagnetism , refers to a set of formal analogies between Maxwell's field equations and an approximation, valid under certain conditions, to the Einstein field equations for general relativity...
, but he knew that Mach’s idea would not work if space goes on forever. In a closed universe, he believed that Mach’s principle would hold.
Mach’s principle has generated much controversy over the years.
Modern quantum theory
In 1917, at the height of his work on relativity, Einstein published an article in Physikalische Zeitschrift that proposed the possibility of stimulated emissionIn optics, stimulated emission is the process by which an electron, perturbed by a photon having the correct energy, may drop to a lower energy level resulting in the creation of another photon. The perturbing photon is seemingly unchanged in the process , and the second photon is created with the...
, the physical process that makes possible the maserA maser is a device that produces coherent electromagnetic waves through amplification due to stimulated emission. Historically the term came from the acronym "Microwave Amplification by Stimulated Emission of Radiation", although modern masers emit over a broad portion of the electromagnetic...
and the laserA laser is a device that emits light through a process called stimulated emission. Laser light is usually spatially coherent, which means that the light either is emitted in a narrow, low-divergence beam, or can be converted into one with the help of optical components such as lenses...
.
This article showed that the statistics of absorption and emission of light would only be consistent with Planck’s distribution law if the emission of light into a mode with n photons would be enhanced statistically compared to the emission of light into an empty mode. This paper was enormously influential in the later development of quantum mechanics, because it was the first paper to show that the statistics of atomic transitions had simple laws.
Einstein discovered Louis de Broglie’s work, and supported his ideas, which were received skeptically at first. In another major paper from this era, Einstein gave a wave equation for de Broglie waves, which Einstein suggested was the Hamilton–Jacobi equation of mechanics. This paper would inspire Schrödinger’s work of 1926.
Bose-Einstein statistics
In 1924, Einstein received a description of a statisticalStatistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force...
model from IndiaIndia, officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal...
n physicist Satyendra Nath BoseSatyendra Nath Bose , FRS, was an Indian physicist, specializing in mathematical physics. He is best known for his work on quantum mechanics in the early 1920s, providing the foundation for Bose-Einstein statistics and the theory of the Bose-Einstein condensate...
, based on a counting method that assumed that light could be understood as a gas of indistinguishable particles. Einstein noted that Bose’s statistics applied to some atoms as well as to the proposed light particles, and submitted his translation of Bose’s paper to the Zeitschrift für PhysikThe European Physical Journal is a joint publication of EDP Sciences, Springer and the Societa Italiana di Fisica. It arose in 1998 as a merger and continuation of Acta Physica Hungarica, Anales de Fisica, Czechoslovak Journal of Physics, Il Nuovo Cimento, Journal de Physique, Portugaliae Physica...
. Einstein also published his own articles describing the model and its implications, among them the Bose-Einstein condensate phenomenon that some particulates should appear at very low temperatures . It was not until 1995 that the first such condensate was produced experimentally by Eric Allin CornellEric Allin Cornell is an American physicist who, along with Carl E. Wieman, was able to synthesize the first Bose-Einstein condensate in 1995...
and Carl WiemanCarl Edwin Wieman is an American physicist at the University of British Columbia and Nobel Prize in Physics laureate for his production in 1995 with Eric Allin Cornell, the first true Bose-Einstein condensate.-Biography:...
using ultra-coolingUltracold atoms is a term used to describe atoms that are maintained at temperatures close to 0 kelvins , typically below some tenths of microkelvins , where their quantum-mechanical properties become important...
equipment built at the NISTThe National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce...
-JILA laboratory at the University of Colorado at BoulderThe University of Colorado at Boulder is a public research university located in Boulder, Colorado. It is the flagship university of the University of Colorado system and was founded five months before Colorado was admitted to the union in 1876...
. Bose-Einstein statistics are now used to describe the behaviors of any assembly of bosonIn particle physics, bosons are particles which obey Bose–Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein. In contrast to fermions, which obey Fermi-Dirac statistics, several bosons can occupy the same quantum state. Thus, bosons with the same energy can occupy the...
s. Einstein’s sketches for this project may be seen in the Einstein Archive in the library of the Leiden UniversityLeiden University , located in the city of Leiden, is the oldest university in the Netherlands. The university was founded in 1575 by Prince William of Orange, leader of the Dutch Revolt in the Eighty Years' War. The royal Dutch House of Orange-Nassau and Leiden University still have a close...
.
Energy momentum pseudotensor
General relativity includes a dynamical spacetime, so it is difficult to see how to identify the conserved energy and momentum. Noether’s theorem allows these quantities to be determined from a LagrangianThe Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics known as Lagrangian mechanics. In classical mechanics, the...
with translation invarianceIn geometry, a translation "slides" an object by a a: Ta = p + a.In physics and mathematics, continuous translational symmetry is the invariance of a system of equations under any translation...
, but general covarianceIn theoretical physics, general covariance is the invariance of the form of physical laws under arbitrary differentiable coordinate transformations...
makes translation invariance into something of a gauge symmetryIn gauge symmetry, 'gauge' means 'measure', and symmetry means 'stays the same'. Geometry is the study of the properties of objects that do not change when they move around. An object is symmetric if some motion leaves it looking the same, for instance, rotating an equilateral triangle through 120...
. The energy and momentum derived within general relativity by Noether’s presecriptions do not make a real tensor for this reason.
Einstein argued that this is true for fundamental reasons, because the gravitational field could be made to vanish by a choice of coordinates. He maintained that the noncovariante energy momentum pseudotensor was in fact the best description of the energy momentum distribution in a gravitational field. This approach has been echoed by Lev LandauLev Davidovich Landau was a prominent Soviet physicist who made fundamental contributions to many areas of theoretical physics...
and Evgeny LifshitzEvgeny Mikhailovich Lifshitz was a leading Soviet physicist from a Jewish origin and the brother of Ilya Mikhailovich Lifshitz...
, and others, and has become standard.
The use of non-covariant objects like pseudotensors was heavily criticized in 1917 by Erwin SchrödingerErwin Rudolf Josef Alexander Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics, especially the Schrödinger equation, for which he received the Nobel Prize in 1933...
and others.
Unified field theory
Following his research on general relativity, Einstein entered into a series of attempts to generalize his geometric theory of gravitation, which would allow the explanation of electromagnetism. In 1950, he described his "unified field theoryIn physics, a unified field theory is a type of field theory that allows all of the fundamental forces between elementary particles to be written in terms of a single field. There is no accepted unified field theory yet, and this remains an open line of research. The term was coined by Albert...
" in a Scientific AmericanScientific American is a popular science magazine published since August 28, 1845, which according to the magazine makes it the oldest continuously published magazine in the United States...
article entitled "On the Generalized Theory of Gravitation." Although he continued to be lauded for his work, Einstein became increasingly isolated in his research, and his efforts were ultimately unsuccessful.
In his pursuit of a unification of the fundamental forces, Einstein ignored some mainstream developments in physics, most notably the strong and weak nuclear forces, which were not well understood until many years after his death. Mainstream physics, in turn, largely ignored Einstein’s approaches to unification. Einstein’s dream of unifying other laws of physics with gravity motivates modern quests for a theory of everythingThe theory of everything is a putative theory of theoretical physics that fully explains and links together all known physical phenomena. Initially, the term was used with an ironic connotation to refer to various overgeneralized theories...
and in particular string theoryString theory is a developing branch of theoretical physics that combines quantum mechanics and general relativity into a quantum theory of gravity...
, where geometrical fields emerge in a unified quantum-mechanical setting.
Wormholes
Einstein collaborated with others to produce a model of a wormholeIn physics, a wormhole is a hypothetical topological feature of spacetime that is fundamentally a 'shortcut' through space and time. Spacetime can be viewed as a 2D surface that, when 'folded' over, allows the formation of a wormhole bridge. A wormhole has at least two mouths that are connected...
. His motivation was to model elementary particles with charge as a solution of gravitational field equations, in line with the program outlined in the paper "Do Gravitational Fields play an Important Role in the Constitution of the Elementary Particles?". These solutions cut and pasted Schwarzschild black holes to make a bridge between two patches.
If one end of a wormhole was positively charged, the other end would be negatively charged. These properties led Einstein to believe that pairs of particles and antiparticles could be described in this way.
Einstein-Cartan theory
In order to incorporate spinning point particles into general relativity, the affine connection needed to be generalized to include an antisymmetric part, called the torsionThe term torsion may refer the following:*In geometry:** Torsion of a curve** Torsion tensor in differential geometry** The closely related concepts of Reidemeister torsion and analytic torsion ** Whitehead torsion*In algebra:** Torsion ** Tor functor* In medicine:** Testicular...
. This modification was made by Einstein and Cartan in the 1920s.
Einstein-Podolsky-Rosen paradox
In 1935, Einstein returned to the question of quantum mechanics. He considered how a measurement on one of two entangled particles would affect the other. He noted, along with his collaborators, that by performing different measurements on the distant particle, either of position or momentum, different properties of the entangled partner could be discovered without disturbing it in any way.
He then used a hypothesis of local realism to conclude that the other particle had these properties already determined. The principle he proposed is that if it is possible to determine what the answer to a position or momentum measurement would be, without in any way disturbing the particle, then the particle actually has values of position or momentum.
This principle distilled the essence of Einstein’s objection to quantum mechanics. As a physical principle, it has since been shown to be incompatible with experiments.
Equations of motion
The theory of general relativity has two fundamental laws—the Einstein equations which describe how space curves, and the geodesic equation which describes how particles move.
Since the equations of general relativity are non-linear, a lump of energy made out of pure gravitational fields, like a black hole, would move on a trajectory which is determined by the Einstein equations themselves, not by a new law. So Einstein proposed that the path of a singular solution, like a black hole, would be determined to be a geodesic from general relativity itself.
This was established by Einstein, Infeld and Hoffmann for pointlike objects without angular momentum, and by Roy KerrRoy Patrick Kerr is a New Zealand mathematician who is best known for discovering the Kerr vacuum, an exact solution to the Einstein field equation of general relativity...
for spinning objects.
Einstein’s mistakes
In addition to his well-accepted results, some of Einstein’s papers contain mistakes:
- 1905: In the original German version of the special relativity paper, and in some English translations, Einstein gives a wrong expression for the transverse mass of a fast moving particle. The transverse mass is the antiquated name for the ratio of the 3-force to the 3-acceleration when the force is perpendicular to the velocity. Einstein gives this ratio as , while the actual value is (corrected by Max Planck).
- 1905: In his PhD dissertation, the friction in dilute solutions has an miscalculated numerical prefactor, which makes the estimate of Avogadro’s number off by a factor of 3. The mistake is corrected by Einstein in a later publication.
- 1905: An expository paper explaining how airplanes fly includes an example which is incorrect. There is a wing which he claims will generate lift. This wing is flat on the bottom, and flat on the top, with a small bump at the center. It is designed to generate lift by Bernoulli’s principle, and Einstein claims that it will. Simple action reaction considerations, though, show that the wing will not generate lift, at least if it is long enough.
- 1911: Einstein predicted how much the sun’s gravity would deflect nearby starlight, but used an approximation which gives an answer which is half as big as the correct one.
- 1913: Einstein started writing papers based on his belief that the hole argument
In general relativity, the hole argument is a "paradox" which much troubled Albert Einstein while developing his famous field equation.It is interpreted by some philosophers as an argument against manifold substantialism, a doctrine that the manifold of events in spacetime are a "substance" which...
made general covariance impossible in a theory of gravity.
- 1922: Einstein published a qualitative theory of superconductivity based on the vague idea of electrons shared in orbits. This paper predated modern quantum mechanics, and is well understood to be completely wrong. The correct BCS theory
BCS theory is the first microscopic theory of superconductivity, proposed by Bardeen, Cooper, and Schrieffer in 1957 since the discovery of superconductivity in 1911. It describes superconductivity as a microscopic effect caused by a condensation of pairs of electrons into a boson-like...
of low temperature superconductivity was only worked out in 1957, thirty years after the establishing of modern quantum mechanics.
- 1937: Einstein believed that the focusing properties of geodesics in general relativity would lead to an instability which causes plane gravitational waves to collapse in on themselves. While this is true to a certain extent in some limits, because gravitational instabilities can lead to a concentration of energy density into black holes, for plane waves of the type Einstein and Rosen considered in their paper, the instabilities are under control. Einstein retracted this position a short time later, but until his death his collaborator Nathan Rosen
Nathan Rosen was an American-Israeli physicist noted for his study on the structure of the hydrogen molecule and his work with Albert Einstein and Boris Podolsky on entangled wave functions and the EPR paradox.-Background:Nathan Rosen was born into a Jewish family in Brooklyn, New York...
maintained that gravitational waves are unstable.
- 1939: Einstein denied that black holes could form several times, the last time in print. He published a paper that argues that a star collapsing would spin faster and faster, spinning at the speed of light with infinite energy well before the point where it is about to collapse into a black hole. This paper received no citations, and the conclusions are well understood to be wrong. Einstein’s argument itself is inconclusive, since he only shows that stable spinning objects have to spin faster and faster to stay stable before the point where they collapse. But it is well understood today (and was understood well by some even then) that collapse cannot happen through stationary states the way Einstein imagined.
In addition to these well established mistakes, there are other arguments whose deduction is considered correct, but whose interpretation or philosophical conclusion is considered to have been incorrect:
- In the Bohr-Einstein debates
The Bohr–Einstein debates is a popular name given to a series of public disputes between Albert Einstein and Niels Bohr about quantum physics. These two men, along with Max Planck were the founders of the original quantum theory. Their "debates" are remembered because of their importance to the...
and the papers following this, Einstein tries to poke holes in the uncertainty principle, ingeniously, but unsuccessfully.
- In the EPR paper
In quantum mechanics, the EPR paradox is a thought experiment which challenged long-held ideas about the relation between the observed values of physical quantities and the values that can be accounted for by a physical theory...
, Einstein concludes that quantum mechanics must be replaced by local hidden variables. The measured violations of Bell’s inequality show that hidden variables, if they exist, must be nonlocal.
Einstein himself considered the use of the "fudge factor" lambda in his 1917 paper founding cosmology as a "blunder". The theory of general relativity predicted an expanding or contracting universe, but Einstein wanted a universe which is an unchanging three dimensional sphere, like the surface of a three dimensional ball in four dimensions. He wanted this for philosophical reasons, so as to incorporate Mach’s principle in a reasonable way. He stabilized his solution by introducing a cosmological constantIn physical cosmology, the cosmological constant was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe...
, and when the universe was shown to be expanding, he retracted the constant as a blunder. This is not really much of a blunder—the cosmological constant is necessary within general relativity as it is currently understood, and it is widely believed to have a nonzero value today.
Einstein took the wrong side in a few scientific debates.
- He briefly flirted with transverse and longitudinal mass concepts, before rejecting them.
- Einstein initially opposed Minkowski’s geometrical formulation of special relativity, changing his mind completely a few years later.
- Based on his cosmological model, Einstein rejected expanding universe solutions by Friedman
Friedman, Friedmann, and Freedman are common surnames.They may refer to:-Art:* Arnold Friedman , an American painter* Drew Friedman, cartoonist* Harold Freedman, artist public murals* Ken Friedman, seminal figure in Fluxus...
and LemaitreLemaître or Lemaitre is a French family name meaning or the master — derived from the Latin word magister.Lemaître:*Frédérick Lemaître, was a French actor and playwright....
as unphysical, changing his mind when the universe was shown to be expanding a few years later.
- Finding it too formal, Einstein believed that Heisenberg’s matrix mechanics
Matrix mechanics is a formulation of quantum mechanics created by Werner Heisenberg, Max Born, and Pascual Jordan in 1925.Matrix mechanics was the first complete and correct definition of quantum mechanics. It extended the Bohr Model by describing how the quantum jumps occur. It did so by...
was incorrect. He changed his mind when Schrödinger and others demonstrated that the formulation in terms of the Schrödinger equationIn physics, specifically quantum mechanics, the Schrödinger equation is an equation that describes how the quantum state of a physical system changes in time...
, based on Einstein’s wave-particle duality was equivalent to Heisenberg’s matrices.
- Einstein rejected work on black holes by Chandrasekhar
Chandrasekhar or Chandra Shekhar is an Indian name and may refer to:In politics and activism:*Chandrasekhar Azad , Indian revolutionary*Chandra Shekhar Singh , former Prime Minister of India...
, OppenheimerOppenheimer as a surname may refer to:* J. Robert Oppenheimer, physicist who headed the Manhattan Project, known as the "Father of the Atomic Bomb"* Frank Oppenheimer, a physicist, brother of J...
, and others, believing, along with Eddington, that collapse past the horizon (then called the ’Schwarzschild singularityIn general relativity, an event horizon is a boundary in spacetime, most often an area surrounding a black hole, beyond which events cannot affect an outside observer...
’) would never happen. So big was his influence, that this opinion was not rejected until the early 1960s, almost a decade after his death.
- Einstein believed that some sort of nonlinear instability could lead to a field theory whose solutions would collapse into pointlike objects which would behave like quantum particles. While there are many field theories with point-like particle solutions, none of them behave like quantum particles. It is widely believed that quantum mechanics would be impossible to reproduce from a local field theory of the type Einstein considered, because of Bell’s inequality.
In addition to these well known mistakes, it is sometimes claimed that the general line of Einstein’s reasoning in the 1905 relativity paper is flawed, or the photon paper, or one or another of the most famous papers. None of these claims are widely accepted.
Collaboration with other scientists
In addition to long time collaborators Leopold InfeldLeopold Infeld was a Polish physicist who worked mainly in Poland and Canada . He was a Rockefeller fellow at Cambridge University and a member of the Polish Academy of Sciences....
, Nathan RosenNathan Rosen was an American-Israeli physicist noted for his study on the structure of the hydrogen molecule and his work with Albert Einstein and Boris Podolsky on entangled wave functions and the EPR paradox.-Background:Nathan Rosen was born into a Jewish family in Brooklyn, New York...
, Peter BergmannPeter Gabriel Bergmann was a German-American physicist best known for his work with Albert Einstein on a unified field theory encompassing all physical interactions. After obtaining his Ph.D at the German University in Prague in 1936 he went to work with Einstein, as his research assistant, at the...
and others, Einstein also had some one-shot collaborations with various scientists.
Einstein-de Haas experiment
Einstein and De Haas demonstrated that magnetization is due to the motion of electrons, nowadays known to be the spin. In order to show this, they reversed the magnetization in an iron bar suspended on a torsion pendulum. They confirmed that this leads the bar to rotate, because the electron’s angular momentum changes as the magnetization changes. This experiment needed to be sensitive, because the angular momentum associated with electrons is small, but it definitively established that electron motion of some kind is responsible for magnetization.
Schrödinger gas model
Einstein suggested to Erwin SchrödingerErwin Rudolf Josef Alexander Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics, especially the Schrödinger equation, for which he received the Nobel Prize in 1933...
that he might be able to reproduce the statistics of a Bose-Einstein gas by considering a box. Then to each possible quantum motion of a particle in a box associate an independent harmonic oscillator. Quantizing these oscillators, each level will have an integer occupation number, which will be the number of particles in it.
This formulation is a form of second quantization, but it predates modern quantum mechanics.Erwin SchrödingerErwin Rudolf Josef Alexander Schrödinger was an Austrian theoretical physicist who achieved fame for his contributions to quantum mechanics, especially the Schrödinger equation, for which he received the Nobel Prize in 1933...
applied this to derive the thermodynamicIn physics, thermodynamics is the study of the conversion of energy into work and heat and its relation to macroscopic variables such as temperature, volume and pressure...
properties of a semiclassicalIn physics, the adjective semiclassical has different precise meanings depending on the context. All these meanings usually refer to some approximation, limit or situation that combines quantum and classical aspects in a given problem...
ideal gasAn ideal gas is a theoretical gas composed of a set of randomly-moving point particles that interact only through elastic collisions. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.At...
. Schrödinger urged Einstein to add his name as co-author, although Einstein declined the invitation.
Einstein refrigerator
In 1926, Einstein and his former student Leó SzilárdLeó Szilárd was a Hungarian physicist who conceived the nuclear chain reaction and worked on the Manhattan Project...
co-invented (and in 1930, patented) the Einstein refrigeratorThe Einstein refrigerator is an absorption refrigerator which has no moving parts and requires only a heat source to operate. It was jointly invented in 1926 by Albert Einstein and his former student Leó Szilárd and patented in the US on November 11 1930 ....
. This Absorption refrigeratorThe absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling system...
was then revolutionary for having no moving parts and using only heat as an input. On 11 November 1930, was awarded to Albert Einstein and Leó Szilárd for the refrigerator. Although the refrigerator was not immediately put into commercial production, the most promising of their patents being quickly bought up by the Swedish company Electrolux to protect its refrigeration technology from competition.
Bohr versus Einstein
In the 1920s, quantum mechanicsQuantum mechanics is a set of principles describing the physical reality at the atomic level of matter and the subatomic . These descriptions include the simultaneous wave-like and particle-like behavior of both matter and radiation...
developed into a more complete theory. Einstein was unhappy with the Copenhagen interpretationThe Copenhagen interpretation is an interpretation of quantum mechanics. A key feature of quantum mechanics is that the state of every particle is described by a wavefunction, which is a mathematical representation used to calculate the probability for it to be found in a location or a state of...
of quantum theory developed by Niels BohrNiels Henrik David Bohr was a Danish physicist who made fundamental contributions to understanding atomic structure and quantum mechanics, for which he received the Nobel Prize in Physics in 1922. Bohr mentored and collaborated with many of the top physicists of the century at his institute in...
and Werner HeisenbergWerner Heisenberg was a German theoretical physicist who made foundational contributions to quantum mechanics and is best known for asserting the uncertainty principle of quantum theory...
. In this interpretation, quantum phenomena are inherently probabilistic, with definite states resulting only upon interaction with classical systems. A public debateThe Bohr–Einstein debates is a popular name given to a series of public disputes between Albert Einstein and Niels Bohr about quantum physics. These two men, along with Max Planck were the founders of the original quantum theory. Their "debates" are remembered because of their importance to the...
between Einstein and Bohr followed, lasting on and off for many years (including during the Solvay ConferenceThe International Solvay Institutes for Physics and Chemistry, located in Brussels, were founded by the Belgian industrialist Ernest Solvay in 1912, following the historic invitation-only 1911 Conseil Solvay, the first world physics conference...
s). Einstein formulated thought experimentA thought experiment, sometimes called a gedankenexperiment in German, is a proposal for an experiment that would test or illuminate a hypothesis or theory....
s against the Copenhagen interpretation, which were all rebutted by Bohr. In a 1926 letter to Max BornMax Born was a German born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...
, Einstein wrote: "I, at any rate, am convinced that He [God] does not throw dice."
Einstein was never satisfied by what he perceived to be quantum theory’s intrinsically incomplete description of nature, and in 1935 he further explored the issue in collaboration with Boris PodolskyBoris Podolsky born in 1896, Taganrog, Russia - died 1966, U.S.), was an American physicist of Russian Jewish descent.-Education:...
and Nathan RosenNathan Rosen was an American-Israeli physicist noted for his study on the structure of the hydrogen molecule and his work with Albert Einstein and Boris Podolsky on entangled wave functions and the EPR paradox.-Background:Nathan Rosen was born into a Jewish family in Brooklyn, New York...
, noting that the theory seems to require non-local interactions; this is known as the EPR paradoxIn quantum mechanics, the EPR paradox is a thought experiment which challenged long-held ideas about the relation between the observed values of physical quantities and the values that can be accounted for by a physical theory...
. The EPR experiment has since been performed, with results confirming quantum theory’s predictions.
Religious views
The question of scientific determinism gave rise to questions about Einstein’s position on theological determinismTheological determinism is a form of determinism which states that all events that happen are pre-ordained, or predestined to happen, by a monotheistic God. Theological determinists exist in a number of religions, including Judaism, Christianity and Islam....
, and whether or not he believed in God, or in a god. In 1929, Einstein told Rabbi Herbert S. GoldsteinHerbert S. Goldstein, , was a prominent American rabbi and Jewish leader.He was the only person in history to have been elected president of the Union of Orthodox Jewish Congregations of America, the Rabbinical Council of America , and the Synagogue Council of America.Globally, he fought for the...
"I believe in Spinoza’s God, who reveals Himself in the lawful harmony of the world, not in a God Who concerns Himself with the fate and the doings of mankind."
Politics
Einstein flouted the ascendant NaziNazism, known officially in German as National Socialism , is the totalitarian ideology and practices of the Nazi Party or National Socialist German Workers’ Party under Adolf Hitler, and the policies adopted by the dictatorial government of Nazi Germany from 1933 to 1945.Nazism is often considered...
movement, tried to be a voice of moderation in the tumultuous formation of the State of IsraelIsrael officially the State of Israel , is a developed state in Western Asia located on the eastern shore of the Mediterranean Sea. It borders Lebanon in the north, Syria in the northeast, Jordan in the east, and Egypt on the southwest, and contains geographically diverse features within its...
and braved anti-communist politics and resistance to the civil rights movement in the United States. He participated in the 1927 congress of the League against ImperialismThe League against Imperialism was founded in the Egmont Palace in Brussels, Belgium, on February 10, 1927, in presence of 175 delegates, among which 107 came from 37 countries under colonial rule. The Congress aimed at creating a "mass anti-imperialist movement" at a world scale, and was...
in Brussels. He was a socialist ZionistLabor Zionism can be described as the major stream of the left wing of the Zionist movement. It was, for many years, a significant tendency among Zionists and Zionist organizational structure and the major stream of the Zionist movement...
who supported the creation of a Jewish national homeland in the British mandate of Palestine.
After World War II, as enmity between the former allies became a serious issue, Einstein wrote, "I do not know how the third World War will be fought, but I can tell you what they will use in the Fourth — rocks!" In a 1949 Monthly ReviewMonthly Review is an independent socialist journal published in New York City. It appears 11 times per year.-History:The publication was founded by Harvard University economics instructor Paul Sweezy, who became the first editor...
article entitled "Why Socialism?" Albert Einstein described a chaotic capitalistCapitalism is an economic and social system in which the means of production are privately controlled; labor, goods and capital are traded in a market; profits are distributed to owners or invested in technologies and industries; and wages are paid to labor...
society, a source of evil to be overcome, as the "predatory phase of human development" . With Albert SchweitzerAlbert Schweitzer was a German-French theologian, musician, philosopher, and physician. He was born in Kaysersberg in the province of Elsass-Lothringen , at the time in the German Empire...
and Bertrand RussellBertrand Arthur William Russell, 3rd Earl Russell, OM, FRS was an English philosopher, logician, mathematician, historian, and social critic. Although he spent the majority of his life in England, he was born in Wales, where he also died.Russell led the British "revolt against idealism" in the...
, Einstein lobbied to stop nuclear testing and future bombs. Days before his death, Einstein signed the Russell-Einstein ManifestoThe Russell–Einstein Manifesto was issued in London on July 9, 1955 by Bertrand Russell in the midst of the Cold War. It highlighted the dangers posed by nuclear weapons and called for world leaders to seek peaceful resolutions to international conflict...
, which led to the Pugwash Conferences on Science and World AffairsThe Pugwash Conferences on Science and World Affairs is an international organization that brings together scholars and public figures to work toward reducing the danger of armed conflict and to seek solutions to global security threats...
.
Einstein was a member of several civil rights groups, including the Princeton chapter of the NAACPThe National Association for the Advancement of Colored People, usually abbreviated as NAACP and pronounced N-double-A-C-P, is one of the oldest and most influential civil rights organizations in the...
. When the aged W. E. B. Du Bois was accused of being a Communist spy, Einstein volunteered as a character witness, and the case was dismissed shortly afterward. Einstein’s friendship with activist Paul RobesonPaul LeRoy Bustill Robeson was an internationally renowned American basso profundo concert singer, scholar, actor of film and stage, All-American and professional athlete, writer, multi-lingual orator and lawyer who was also noted for his wide-ranging social justice activism...
, with whom he served as co-chair of the American Crusade to End LynchingThe American Crusade Against Lynching was an organization, created in 1946 and headed by Paul Robeson, dedicated to eliminating lynching in the United States. Many prominent intellectuals were members, including Albert Einstein. The organization was labeled a "communist front" by the FBI, and...
, lasted twenty years.
Death
On 17 April 1955, Albert Einstein experienced internal bleeding caused by the rupture of an abdominal aortic aneurysmAbdominal aortic aneurysm is a localized dilatation of the abdominal aorta exceeding the normal diameter by more than 50 percent. It is caused by degeneration of the aortic wall, but the exact etiology remains unknown...
, which had previously been reinforced surgically by Dr. Rudolph NissenNissen fundoplication is a surgical procedure to treat gastroesophageal reflux disease and hiatus hernia. In GERD it is usually performed when medical therapy has failed, but with paraesophageal hiatus hernia, it is the first-line procedure...
in 1948. He took the draft of a speech he was preparing for a television appearance commemorating the State of Israel’s seventh anniversary with him to the hospital, but he did not live long enough to complete it. Einstein refused surgery, saying: "I want to go when I want. It is tasteless to prolong life artificially. I have done my share, it is time to go. I will do it elegantly." He died in Princeton Hospital early the next morning at the age of 76, having continued to work until near the end. Einstein’s remains were cremated and his ashes were scattered around the grounds of the Institute for Advanced Study, Princeton, New Jersey.
During the autopsy, the pathologist of Princeton Hospital, Thomas Stoltz HarveyThomas Stoltz Harvey was a pathologist who conducted the autopsy on Albert Einstein in 1955. He kept Einstein's brain after the autopsy, apparently without permission from the Einstein family. The managing director of the Einstein Memorial Hospital expected Dr. Harvey to write a report on...
removed Einstein’s brain for preservation, without the permission of his family, in hope that the neuroscience of the future would be able to discover what made Einstein so intelligent.
Legacy
While travelling, Einstein had written daily to his wife Elsa and adopted stepdaughters, Margot and Ilse, and the letters were included in the papers bequeathed to The Hebrew University. Margot Einstein permitted the personal letters to be made available to the public, but requested that it not be done until twenty years after her death (she died in 1986). Barbara Wolff, of The Hebrew University’s Albert Einstein Archives, told the BBCThe British Broadcasting Corporation, usually referred to by its abbreviation as the "BBC", is the longest established and largest broadcaster in the world...
that there are about 3,500 pages of private correspondence written between 1912 and 1955.
The United States’ National Academy of SciencesThe National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine."The group holds a congressional charter under Title 36 of the United States Code....
commissioned the Albert Einstein MemorialThe Albert Einstein Memorial is a monumental bronze statue depicting Albert Einstein seated with manuscript papers in hand. It is located in central Washington, D.C., United States, in a grove of trees at the southwest corner of the grounds of the National Academy of Sciences on Constitution...
, a monumental bronze and marble sculpture by Robert BerksRobert Berks is an American sculptor, industrial designer and planner. He has created hundreds of bronze sculptures and monuments including the Mary McLeod Bethune memorial and the Albert Einstein Memorial in Washington, D.C....
, dedicated in 1979 at its Washington, D.C.Washington, D.C. , formally the District of Columbia and commonly referred to as Washington, the District, or simply D.C., is the capital of the United States, founded on July 16, 1790...
campus adjacent to the National MallThe National Mall is an open-area national park in downtown Washington, D.C., the capital of the United States. The National Mall is a unit of the National Park Service, and is administered by the National Mall and Memorial Parks unit...
.
Einstein bequeathed the royalties from use of his imagePersonality rights is a common or casual reference to the proper term of art "Right of Publicity." The Right of Publicity can be defined simply as the right of an individual to control the commercial use of his or her name, image, likeness or other unequivocal aspects of one's identity...
to The Hebrew University of Jerusalem. CorbisCorbis Corporation is an American company, based in Seattle, Washington, that sells and otherwise distributes photography and film footage and related rights...
, successor to The Roger Richman AgencyThe Roger Richman Agency, Inc. was a licensing agency that specialises in personality rights. It licenses the use of the imagery, persona and likeness of various well known entertainment celebrities and historical personalities...
, licenses the use of his name and associated imagery, as agent for the Hebrew University.
Effect on popular culture
In the period before World War II, Albert Einstein was so well-known in America that he would be stopped on the street by people wanting him to explain "that theory." He finally figured out a way to handle the incessant inquiries. He told his inquirers "Pardon me, sorry! Always I am mistaken for Professor Einstein."
Albert Einstein has been the subject of or inspiration for many novels, films, and plays. Einstein is a favorite model for depictions of mad scientistA mad scientist is a stock character of popular fiction, specifically science fiction. The mad scientist may be villainous, benign or neutral, and whether insane, eccentric, or simply bumbling, mad scientists often work with fictional technology in order to forward their schemes, if they even have...
s and absent-minded professorThe absent-minded professor is a stock character of popular fiction, usually portrayed as a talented academic whose focus on academic matters leads them to ignore or forget their surroundings....
s; his expressive face and distinctive hairstyle have been widely copied and exaggerated. TimeTime is an American newsmagazine. A European edition is published from London. Time Europe covers the Middle East, Africa and, since 2003, Latin America. An Asian edition is based in Hong Kong. As of 2009, Time no longer publishes a Canadian advertiser edition...
magazine’s Frederic Golden wrote that Einstein was "a cartoonist’s dream come true."
Einstein’s association with great intelligence has made the name Einstein synonymous with genius, often used in ironicIrony is a situation, literary or rhetorical device, in which there is an incongruity, discordance or unintended connection that goes beyond the most evident meaning....
expressions such as "Nice job, Einstein!"
Awards
In 1922, Einstein was awarded the 1921 Nobel Prize in PhysicsThe Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in chemistry, Nobel Prize in literature, Nobel Peace Prize, and...
, "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect". This refers to his 1905 paper on the photoelectric effect, "On a Heuristic Viewpoint Concerning the Production and Transformation of Light", which was well supported by the experimental evidence by that time. The presentation speech began by mentioning "his theory of relativity [which had] been the subject of lively debate in philosophical circles [and] also has astrophysical implications which are being rigorously examined at the present time."
It was long reported that Einstein gave the Nobel prize money directly to his first wife, Mileva MarićMileva Marić was one of the first women to study mathematics and physics in Europe...
, in compliance with their 1919 divorce settlement. However, personal correspondence made public in 2006 shows that he invested much of it in the United States, and saw much of it wiped out in the Great DepressionThe Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...
.
Einstein traveled to New York CityNew York is the most populous city in the United States, and the center of the New York metropolitan area, which is among the most populous urban areas in the world. A leading global city, New York exerts a powerful influence over worldwide commerce, finance, culture, fashion and entertainment...
in the United States for the first time on 2 April, 1921. When asked where he got his scientific ideas, Einstein explained that he believed scientific work best proceeds from an examination of physical reality and a search for underlying axioms, with consistent explanations that apply in all instances and avoid contradicting each other. He also recommended theories with visualizable results .
In 1999, Albert Einstein was named Person of the Century by TimeTime is an American newsmagazine. A European edition is published from London. Time Europe covers the Middle East, Africa and, since 2003, Latin America. An Asian edition is based in Hong Kong. As of 2009, Time no longer publishes a Canadian advertiser edition...
magazine, a Gallup pollThe Gallup Poll is the division of Gallup that regularly conducts public opinion polls in more than 140 countries around the world. Gallup Polls are often referenced in the mass media as a reliable and objective measure of public opinion...
recorded him as the fourth most admired person of the 20th century in the U.S. and according to The 100: A Ranking of the Most Influential Persons in HistoryThe 100: A Ranking of the Most Influential Persons in History is a 1978 book by Michael H. Hart. It is a ranking of the 100 people who most influenced human history....
, Einstein is "the greatest scientist of the twentieth century and one of the supreme intellects of all time."
Honors
Albert Einstein has been recognized many times over for his achievements. The International Union of Pure and Applied PhysicsThe International Union of Pure and Applied Physics is an international non-governmental organization devoted to the advancement of physics...
named 2005 the "World Year of Physics" in commemoration of the 100th anniversary of the publication of the Annus Mirabilis Papers.
The Albert Einstein Memorial in central Washington, D.C.Washington, D.C. , formally the District of Columbia and commonly referred to as Washington, the District, or simply D.C., is the capital of the United States, founded on July 16, 1790...
is a monumental bronzeBronze is a metal alloy consisting primarily of copper, usually with tin as the main additive, but sometimes with other elements such as phosphorus, manganese, aluminium, or silicon. It was particularly significant in antiquity, giving its name to the Bronze Age...
statueA statue is a sculpture in the round representing a person or persons, an animal, or an event, normally full-length, as opposed to a bust, and at least close to life-size, or larger...
depicting Einstein seated with manuscript papers in hand. The statue is located in a grove of trees at the southwest corner of the grounds of the National Academy of SciencesThe National Academy of Sciences is a corporation in the United States whose members serve pro bono as "advisers to the nation on science, engineering, and medicine."The group holds a congressional charter under Title 36 of the United States Code....
on Constitution AvenueIn Washington, D.C., Constitution Avenue is a major east-west street running just north of the United States Capitol in the city's Northwest and Northeast quadrants...
, near the Vietnam Veterans MemorialThe Vietnam Veterans Memorial is a national war memorial in Washington, D.C. It honors members of the U.S. armed forces who fought in the Vietnam War and who died in service or are still unaccounted for....
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The chemical elementA chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.Common examples of elements...
99, einsteiniumEinsteinium is a metallic synthetic element. On the periodic table, it is represented by the symbol Es and atomic number 99. It is the seventh transuranic element, and an actinoid. It was named in honor of Albert Einstein.-Properties:...
, was named for him in August 1955, four months after Einstein’s death.
In 1999 TimeTime is an American newsmagazine. A European edition is published from London. Time Europe covers the Middle East, Africa and, since 2003, Latin America. An Asian edition is based in Hong Kong. As of 2009, Time no longer publishes a Canadian advertiser edition...
magazine named him the Person of the Century, beating contenders like Mahatma GandhiMohandas Karamchand Gandhi was the pre-eminent political and spiritual leader of India during the Indian independence movement...
and Franklin Roosevelt, and in the words of a biographer, “to the scientifically literate and the public at large, Einstein is synonymous with genius.”
2001 Einstein is an inner main belt asteroidthumb|260px|right|[[253 Mathilde]], a [[C-type asteroid]] measuring about across. Photograph taken in 1997 by the [[NEAR Shoemaker]] probe.Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are...
discovered on March 5, 1973.
The Albert Einstein Award (sometimes called the Albert Einstein Medal because it is accompanied with a gold medal) is an award in theoretical physicsTheoretical physics is a branch of physics which employs mathematical models and abstractions of physics in an attempt to explain natural phenomena. Its central core is mathematical physics,[Sometimes mathematical physics and theoretical physics are used synonymously to refer to the...]
, that was established to recognize high achievement in the natural sciences. It was endowed by the Lewis and Rosa Strauss Memorial Fund in honor of Albert Einstein’s 70th birthday. It was first awarded in 1951 and included a prize money of $ 15,000, which was later reduced to $ 5,000. The winner is selected by a committee (the first of which consisted of Einstein, OppenheimerJ. Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. He is best known for his role as the scientific director of the Manhattan Project, the World War II effort to develop the first nuclear weapons at the secret Los Alamos...
, von NeumannJohn von Neumann was a Hungarian American mathematician who made major contributions to a vast range of fields, including set theory, functional analysis, quantum mechanics, ergodic theory, continuous geometry, economics and game theory, computer science, numerical analysis, hydrodynamics John...
and WeylHermann Klaus Hugo Weyl was a German mathematician. Although much of his working life was spent in Zürich, Switzerland and then Princeton, he is associated with the University of Göttingen tradition of mathematics, represented by David Hilbert and Hermann Minkowski.His research has had major...
) of the Institute for Advanced StudyThe Institute for Advanced Study, located in Princeton, New Jersey, United States, is a center for theoretical research and intellectual inquiry. The Institute is perhaps best known as the academic home of Albert Einstein, John von Neumann, and Kurt Gödel, after their immigration to the United...
, which administers the award. Lewis L. Strauss used to be one of the trustees of the institute.
The Albert Einstein Peace Prize is an award that is given yearly by the Chicago, Illinois-based Albert Einstein Peace Prize Foundation. Winners of the prize receive $ 50,000.
In 1990, his name was added to the Walhalla templeThe Walhalla is a hall of fame for "laudable and distinguished Germans" resp. "famous personalities in German history – politicians, sovereigns, scientists and artists" "of the German tongue", housed in a neo-classical building above the Danube River east of Regensburg, in Bavaria, Germany...
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Publications
- The following publications by Albert Einstein are referenced in this article. A more complete list of his publications may be found at List of scientific publications by Albert Einstein.
Further reading
- Moring, Gary (2004): The complete idiot’s guide to understanding Einstein ( 1st ed. 2000). Indianapolis IN : Alpha books (Macmillan USA). ISBN 0028631803
- Abraham Pais
Abraham Pais was a Dutch-born American physicist and science historian. Pais earned his Ph.D. from University of Utrecht just prior to a Nazi ban on Jewish participation in Dutch universities during World War II...
(1982): Subtle is the Lord: The science and the life of Albert Einstein. Oxford University Press. The definitive biography to date.
- -------- (1994): Einstein Lived Here. Oxford University Press.
- Parker, Barry (2000): Einstein’s Brainchild. Prometheus Books. A review of Einstein’s career and accomplishments, written for the lay public.
- Schweber, Sylvan S. (2008): Einstein and Oppenheimer: The Meaning of Genius. Harvard University Press. ISBN 978-0674028289.
External links
Retrieved on 2009-06-12
- Works by Albert Einstein (public domain in Canada)
- Why Socialism? by Albert Einstein, Monthly Review
Monthly Review is an independent socialist journal published in New York City. It appears 11 times per year.-History:The publication was founded by Harvard University economics instructor Paul Sweezy, who became the first editor...
, May 1949
- Nobelprize.org Biography:Albert Einstein