Who was Albert Einstein
Albert Einstein (Ulm, 1879–Princeton, 1955) was a theoretical physicist educated in Switzerland. His career took him through Bern, Zurich, Prague and Berlin before settling in the United States. Relativity and the photoelectric effect belong to a body of work that also encompasses statistical and quantum physics. [2]
Childhood and education
He grew up in Munich and joined his family in Italy before attempting the Zurich Polytechnic entrance examination in 1895. His mathematics and science results were strong, but his overall performance was insufficient. He completed secondary schooling in Aarau. This record contradicts the familiar story that he was poor at mathematics. [5]
From 1896 to 1900 he trained at the Polytechnic as a mathematics and science teacher. His fellow students included Marcel Grossmann and Mileva Marić. He also studied independently, particularly Maxwell’s electromagnetism and Hertz’s work. The relationships and reading of those years reappeared throughout his scientific career. [6]
Bern, patents and doctorate
He became a Swiss citizen in 1901 and, after temporary teaching jobs, was appointed a third-class technical expert at the Bern Patent Office in June 1902. He continued scientific research outside a university post. In 1905 he produced five important works on atoms, light quanta and relativity. [7]
He submitted A New Determination of Molecular Dimensions to the University of Zurich in 1905. His doctoral certificate was issued on 15 January 1906. The research belongs to his celebrated publication year, while the formal award followed the next year. The doctorate came from the university rather than the Polytechnic. [8]
1905: light, atoms and Brownian motion
He proposed that light could exchange energy in quanta, helping explain electron emission from illuminated metals. He also explained the irregular motion of particles suspended in liquid through collisions with its molecules. His analysis of Brownian motion connected microscopic observations with the physical reality of atoms. [9]
Special relativity: space and time
Special relativity holds that physical laws are the same for all inertial observers and that each measures the same speed of light in vacuum. An inertial observer moves without acceleration. These principles replace absolute rest with an account of measurements made in different reference frames. [10]
Simultaneity and duration depend on relative motion: events simultaneous for one observer need not be simultaneous for another. Moving clocks exhibit time dilation relative to the frame observing them. These are testable physical statements, rather than a philosophical claim that every description of the world is equally valid. [11]
What E = mc² means
Mass–energy equivalence relates quantities previously treated separately. For a body at rest, its rest energy equals its mass multiplied by the square of the speed of light. The equation expresses a physical relationship; by itself it is not a design for a reactor or a weapon. [12]
Academic career and collaboration with Grossmann
He became a professor in Zurich in 1909, Prague in 1911 and ETH Zurich from 1912 to 1914. [2] At ETH he worked with Marcel Grossmann on gravitation. Their mathematical collaboration contributed to the route towards general relativity, whose final formulation still required problems left unresolved in Zurich to be settled. [13]
General relativity and experimental tests
The equivalence principle provided a starting point: within a sufficiently small region, free fall allows phenomena to be described approximately as though gravity were absent. Einstein developed a theory relating gravitation to spacetime geometry, extending the framework of special relativity. [14]
Following the 1915 formulation, expeditions to Sobral and Príncipe observed the May 1919 solar eclipse to measure starlight deflection near the Sun. Results announced in November supported the relativistic prediction and brought wider recognition. The test depended on astronomical teams as well as Einstein’s theoretical work. [15]
Gravitational waves and cosmology
Gravitational waves were directly detected by LIGO: its Livingston and Hanford instruments recorded a signal from two merging black holes on 14 September 2015. The announcement followed in February 2016. Measuring these spacetime disturbances opened a new way to investigate the universe. [16]
In 1917 he applied general relativity to a homogeneous, static universe, introducing the cosmological constant to counter gravitational contraction. Friedmann showed in 1922 that the equations also allowed dynamic universes. In 1927 Lemaître combined theory and observations to argue for expansion, taking cosmology beyond Einstein’s initial model. [17]
The Nobel Prize in Physics
He received the Nobel Prize in Physics for 1921, awarded in 1922 after being reserved. The citation emphasised theoretical physics and especially the law of the photoelectric effect. It was not an award specifically for relativity, highlighting the importance of his less popularly familiar quantum research. [4]
Bose, stimulated emission and quantum physics
In 1924 Satyendra Nath Bose sent him work on photon statistics. Einstein helped publish it and extended the ideas to atoms in 1924–1925, predicting a collective state at very low temperatures. The name Bose–Einstein condensate preserves both contributions; its experimental realisation came from a later generation of researchers. [18]
Stimulated emission provided another lasting foundation: suitable radiation can induce further emission from an excited system. Decades later, this principle enabled masers and lasers. NIST distinguishes the theoretical basis from devices developed by Townes, Schawlow and Maiman. Einstein contributed the physical principle rather than the first working laser. [19]
The Einstein–Podolsky–Rosen debate
In 1935 he published an argument with Boris Podolsky and Nathan Rosen about the completeness of quantum description. They examined predictions about one system based on measurements of another with which it had interacted. The paper challenged the wave function’s sufficiency as a description of reality rather than rejecting all quantum-physics results. [20]
Inventions and collaboration with Szilard
US patent 1,781,541, granted to Einstein and Leo Szilard on 11 November 1930, describes absorption refrigeration. Its technical example uses butane, ammonia and water: evaporation absorbs heat, water removes ammonia from the mixture, and heating releases it again to sustain the cycle. [21]
Princeton and the search for a unified theory
In 1933 he joined the Institute for Advanced Study at Abraham Flexner’s invitation. He was among its first faculty members and remained associated with it until his death in 1955. Much of this period was devoted to a unified field theory. IAS is independent of Princeton University. [3, 30]
His move to the United States was connected to rejection of the Nazi regime and persecution in Europe. He assisted Jewish and other victims and became a US citizen in 1940. His public activity included civil liberties and disarmament, alongside pacifist views that changed in response to the threat of war. [22]
Scientific responsibility and nuclear weapons
The letter he signed on 2 August 1939 warned the US presidency about nuclear chain reactions and the possibility of extremely powerful bombs. It was an intervention with government about a technological threat, distinct from subsequent weapons design and manufacturing. [23]
Public education and final manifesto
In 1946 he established the Emergency Committee of Atomic Scientists with Leo Szilard and chaired it. A November 1947 letter preserved by the National Archives documents his advocacy of public education about atomic energy and international cooperation to control its risks. It records the evolution of his public responsibility after the war. [24]
He was one of eleven signatories to the Russell–Einstein Manifesto, presented in London on 9 July 1955 after his death. It warned against nuclear war and called for peaceful settlement of conflicts, helping lead to the scientific meeting held in Pugwash in 1957. [25]
Books and public understanding
Relativity: The Special and the General Theory introduced his ideas to readers without advanced mathematics and appeared in numerous editions and translations. [26] In 1938 he published The Evolution of Physics with Leopold Infeld, tracing the development of physical concepts from early formulations to relativity and quanta. [27]
Documentary legacy and institutions
Einstein participated in founding the Hebrew University of Jerusalem, its early academic bodies and its initial scientific activities. He bequeathed his personal papers and literary estate to it. The archive supports documentary study of his research, correspondence and public interventions beyond the images and quotations associated with his public persona. [28]
Caltech’s Einstein Papers Project prepares scholarly editions of his writings and letters, combining transcription, context and annotation with digital discovery tools. This work helps distinguish Einstein’s own words from later recollections, uncertain attributions and popular reconstructions of his life. [29]
