Albert Einstein and His TheoriesEinstein, Albert (1879-1955), German-born American physicist and Nobellaureate, best known as the creator of the special and general theories ofrelativity and for his bold hypothesis concerning the particle nature of light.He is perhaps the most well-known scientist of the 20th century.Einstein was born in Ulm on March 14, 1879, and spent his youth inMunich, where his family owned a small shop that manufactured electric machinery.He did not talk until the age of three, but even as a youth he showed abrilliant curiosity about nature and an ability to understand difficultmathematical concepts. At the age of 12 he taught himself Euclidean geometry.
Einstein hated the dull regimentation and unimaginative spirit of schoolin Munich. When repeated business failure led the family to leave Germany forMilan, Italy, Einstein, who was then 15 years old, used the opportunity towithdraw from the school. He spent a year with his parents in Milan, and when itbecame clear that he would have to make his own way in the world, he finishedsecondary school in Arrau, Switzerland, and entered the Swiss NationalPolytechnic in Zrich. Einstein did not enjoy the methods of instruction there.He often cut classes and used the time to study physics on his own or to playhis beloved violin. He passed his examinations and graduated in 1900 by studyingthe notes of a classmate. His professors did not think highly of him and wouldnot recommend him for a university position.For two years Einstein worked as a tutor and substitute teacher.
In 1902he secured a position as an examiner in the Swiss patent office in Bern. In 1903he married Mileva Mari, who had been his classmate at the polytechnic. They hadtwo sons but eventually divorced. Einstein later remarried.Early Scientific PublicationsIn 1905 Einstein received his doctorate from the University of Zrichfor a theoretical dissertation on the dimensions of molecules, and he alsopublished three theoretical papers of central importance to the development of20th-century physics. In the first of these papers, on Brownian motion, he madesignificant predictions about the motion of particles that are randomlydistributed in a fluid.
These predictions were later confirmed by experiment.The second paper, on the photoelectric effect, contained a revolutionaryhypothesis concerning the nature of light. Einstein not only proposed that undercertain circumstances light can be considered as consisting of particles, but healso hypothesized that the energy carried by any light particle, called a photon,is proportional to the frequency of the radiation. The formula for this is E =hu, where E is the energy of the radiation, h is a universal constant known asPlanck’s constant, and u is the frequency of the radiation. This proposal-thatthe energy contained within a light beam is transferred in individual units, orquanta-contradicted a hundred-year-old tradition of considering light energy amanifestation of continuous processes. Virtually no one accepted Einstein’sproposal. In fact, when the American physicist Robert Andrews Millikanexperimentally confirmed the theory almost a decade later, he was surprised andsomewhat disquieted by the outcome.
Einstein, whose prime concern was to understand the nature ofelectromagnetic radiation, subsequently urged the development of a theory thatwould be a fusion of the wave and particle models for light. Again, very fewphysicists understood or were sympathetic to these ideas.Einstein’s Special Theory of RelativityEinstein’s third major paper in 1905, “On the Electrodynamics of MovingBodies,” contained what became known as the special theory of relativity.
Sincethe time of the English mathematician and physicist Sir Isaac Newton, naturalphilosophers (as physicists and chemists were known) had been trying tounderstand the nature of matter and radiation, and how they interacted in someunified world picture. The position that mechanical laws are fundamental hasbecome known as the mechanical world view, and the position that electrical lawsare fundamental has become known as the electromagnetic world view. Neitherapproach, however, is capable of providing a consistent explanation for the wayradiation (light, for example) and matter interact when viewed from differentinertial frames of reference, that is, an interaction viewed simultaneously byan observer at rest and an observer moving at uniform speed.In the spring of 1905, after considering these problems for ten years,Einstein realized that the crux of the problem lay not in a theory of matter butin a theory of measurement. At the heart of his special theory of relativity wasthe realization that all measurements of time and space depend on judgments asto whether two distant events occur simultaneously. This led him to develop atheory based on two postulates: the principle of relativity, that physical lawsare the same in all inertial reference systems, and the principle of theinvariance of the speed of light, that the speed of light in a vacuum is auniversal constant.
He was thus able to provide a consistent and correctdescription of physical events in different inertial frames of reference withoutmaking special assumptions about the nature of matter or radiation, or how theyinteract. Virtually no one understood Einstein’s argument.Early Reactions to EinsteinThe difficulty that others had with Einstein’s work was not because itwas too mathematically complex or technically obscure; the problem resulted,rather, from Einstein’s beliefs about the nature of good theories and therelationship between experiment and theory. Although he maintained that the onlysource of knowledge is experience, he also believed that scientific theories arethe free creations of a finely tuned physical intuition and that the premises onwhich theories are based cannot be connected logically to experiment. A goodtheory, therefore, is one in which a minimum number of postulates is required toaccount for the physical evidence. This sparseness of postulates, a feature ofall Einstein’s work, was what made his work so difficult for colleagues tocomprehend, let alone support.
Einstein did have important supporters, however. His chief early patronwas the German physicist Max Planck. Einstein remained at the patent office forfour years after his star began to rise within the physics community.
He thenmoved rapidly upward in the German-speaking academic world; his first academicappointment was in 1909 at the University of Zrich. In 1911 he moved to theGerman-speaking university at Prague, and in 1912 he returned to the SwissNational Polytechnic in Zrich. Finally, in 1913, he was appointed director ofthe Kaiser Wilhelm Institute for Physics in Berlin.The General Theory of RelativityEven before he left the patent office in 1907, Einstein began work onextending and generalizing the theory of relativity to all coordinate systems.
He began by enunciating the principle of equivalence, a postulate thatgravitational fields are equivalent to accelerations of the frame of reference.For example, people in a moving elevator cannot, in principle, decide whetherthe force that acts on them is caused by gravitation or by a constantacceleration of the elevator. The full general theory of relativity was notpublished until 1916. In this theory the interactions of bodies, whichheretofore had been ascribed to gravitational forces, are explained as theinfluence of bodies on the geometry of space-time (four-dimensional space, amathematical abstraction, having the three dimensions from Euclidean space andtime as the fourth dimension).
On the basis of the general theory of relativity, Einstein accounted forthe previously unexplained variations in the orbital motion of the planets andpredicted the bending of starlight in the vicinity of a massive body such as thesun. The confirmation of this latter phenomenon during an eclipse of the sun in1919 became a media event, and Einstein’s fame spread worldwide.For the rest of his life Einstein devoted considerable time togeneralizing his theory even more.
His last effort, the unified field theory,which was not entirely successful, was an attempt to understand all physicalinteractions-including electromagnetic interactions and weak and stronginteractions-in terms of the modification of the geometry of space-time betweeninteracting entities.Most of Einstein’s colleagues felt that these efforts were misguided.Between 1915 and 1930 the mainstream of physics was in developing a newconception of the fundamental character of matter, known as quantum theory. Thistheory contained the feature of wave-particle duality (light exhibits theproperties of a particle, as well as of a wave) that Einstein had earlier urgedas necessary, as well as the uncertainty principle, which states that precisionin measuring processes is limited. Additionally, it contained a novel rejection,at a fundamental level, of the notion of strict causality.
Einstein, however,would not accept such notions and remained a critic of these developments untilthe end of his life. “God,” Einstein once said, “does not play dice with theworld.”World CitizenAfter 1919, Einstein became internationally renowned. He accrued honorsand awards, including the Nobel Prize in physics in 1921, from various worldscientific societies. His visit to any part of the world became a nationalevent; photographers and reporters followed him everywhere. While regretting hisloss of privacy, Einstein capitalized on his fame to further his own politicaland social views.
The two social movements that received his full support were pacifismand Zionism. During World War I he was one of a handful of German academicswilling to publicly decry Germany’s involvement in the war. After the war hiscontinued public support of pacifist and Zionist goals made him the target ofvicious attacks by anti-Semitic and right-wing elements in Germany. Even hisscientific theories were publicly ridiculed, especially the theory of relativity.When Hitler came to power, Einstein immediately decided to leave Germanyfor the United States. He took a position at the Institute for Advanced Study atPrinceton, New Jersey. While continuing his efforts on behalf of world Zionism,Einstein renounced his former pacifist stand in the face of the awesome threatto humankind posed by the Nazi regime in Germany.
In 1939 Einstein collaborated with several other physicists in writing aletter to President Franklin D. Roosevelt, pointing out the possibility ofmaking an atomic bomb and the likelihood that the German government wasembarking on such a course. The letter, which bore only Einstein’s signature,helped lend urgency to efforts in the U.S.
to build the atomic bomb, butEinstein himself played no role in the work and knew nothing about it at thetime.After the war, Einstein was active in the cause of internationaldisarmament and world government. He continued his active support of Zionism butdeclined the offer made by leaders of the state of Israel to become president ofthat country. In the U.
S. during the late 1940s and early ’50s he spoke out onthe need for the nation’s intellectuals to make any sacrifice necessary topreserve political freedom. Einstein died in Princeton on April 18, 1955.Einstein’s efforts in behalf of social causes have sometimes been viewedas unrealistic. In fact, his proposals were always carefully thought out.
Likehis scientific theories, they were motivated by sound intuition based on ashrewd and careful assessment of evidence and observation. Although Einsteingave much of himself to political and social causes, science always came first,because, he often said, only the discovery of the nature of the universe wouldhave lasting meaning. His writings include Relativity: The Special and GeneralTheory (1916); About Zionism (1931); Builders of the Universe (1932); Why War?(1933), with Sigmund Freud; The World as I See It (1934); The Evolution ofPhysics (1938), with the Polish physicist Leopold Infeld; and Out of My LaterYears (1950). Einstein’s collected papers are being published in a multivolumework, beginning in 1987.