About Albert Einstein

He is one of the few real pop stars in science: Albert Einstein, born 1879 in Ulm, Germany. This website is named after him – and that is because Einstein Online evolves around Einstein’s presumably most important contribution to science: the general theory of relativity. But who was the person behind the most successful theory of gravitation, space and time to this day?

Albert Einstein is born in Ulm, Germany, on March 14, 1879. During his childhood, the family moves to Munich – Einstein will stay there until the age of 15. He dislikes the authority-ridden school system and tends to be a pain in the teachers’ necks. Albert leaves his school and Munich behind without a diploma. After staying in Milan with his family, he moves to Switzerland and resumes his school education. In contrast to what rumors say, Einstein excels at school with very good grades in natural sciences and mathematics. In 1896, he obtains his high school diploma. Likely to avoid having to do military service, he gives up German citizenship and registers with no religious affiliation, despite his Jewish roots. Until he is granted Swiss citizenship in 1901, he is stateless.

In 1896, he enrolls at the federal polytechnic school in Zurich for a mathematics and physics teaching program. He meets talented scientists and mathematicians, many of whom become his friends, and falls in love with his classmate Mileva Marić. The two will later get married and have one daughter (*1902) and two sons (*1904, *1910).

Mileva Maric and Albert Einstein — Mileva Marić and Albert Einstein in Prague. Source: ETH Zurich, Image Archive Online / author: unknown / Portr_03106 / Public Domain Mark

At the patent office in Bern

When Einstein graduates in 1900, his applications as a scientific assistant at different universities are without success, wherefore he makes his living as a home teacher. It isn’t until two years after finishing his studies, in summer 1902, that he manages to obtain a position as a technical expert at the patent office in Bern. There, he writes four groundbreaking papers within a few months of the year 1905 – which is why this year has become known as the „Annus Mirabilis“, the miracle year. These four papers of 1905 are a proof of Einstein’s genius:

„On a Heuristic Viewpoint Concerning the Production and Transformation of Light”, describing the photoelectric effect,
his dissertation „A New Determination of Molecular Dimensions“, in which he determines the size of sugar molecules and derives a value for the Avogardro constant,
a work on Brownian motion: „On the Motion of Small Particles Suspended in a Stationary Liquid, as Required by the Molecular Kinetic Theory of Heat“, and ultimately
the article „On the Electrodynamics of Moving Bodies“ with the addendum „Does the Inertia of a Body Depend Upon Its Energy Content?“ In this article, Einstein deduces the famous equation E = mc².

In the last two papers, Einstein describes the basic concepts of the so-called special theory of relativity. Max Planck, himself one of the fathers of the equally revolutionary theory of quantum mechanics, is one of the first to realize the significance of Einstein’s discovery. When Planck becomes presidium member of the Prussian Academy of Sciences, he will call Einstein to Berlin one decade later.

Einstein, however, only hesitantly leaves his Swiss home. After his habilitation at the University of Bern, he gets a call from Prague, but returns to the confederates only one and a half years later. He assumes a professorship at Zurich University and makes a name for himself with his unconventional lectures. In 1914, he gives in to Planck’s solicitations and moves with his family to Berlin.

Einstein’s time in Berlin

Einstein develops his general theory of relativity between 1908 and 1915, step by step and with the help of his companions like his former fellow student Marcel Grossmann and his former teacher Hermann Minkowski. However, he does not finalize his work until he arrives in Berlin. In the absence of teaching obligations, he devotes himself entirely to his research until it is mature enough for publication. In March 1916, he releases his overview article „The Foundation of the General Theory of Relativity“. This revolutionary theory of space, time and matter is experimentally confirmed in 1919, when Arthur Eddington measures the light deflection by the gravity of the sun during a solar eclipse. Overnight, the entire world knows about Albert Einstein.

Albert Einstein in front of a blackboard — Albert Einstein 1921. Photograph by Ferdinand Schmutzer (Wikimedia Commons, Public Domain)

Einstein’s private life, in contrast, holds much fewer accomplishments during this time. His marriage is in a deep crisis. His wife Mileva moves back to Switzerland with their children soon after their arrival in Berlin. Einstein, who is already flirting with his cousin Elsa, pushes for a divorce. In 1917, Einstein falls sick and continues to struggle in the following years. Elsa takes care of him. When in 1919, Mileva agrees to divorce him, Einstein marries his cousin. However, in the event that he would win a nobel prize, he promises the money to his first wife.

Therefore, Mileva, too, must have felt quite excited when in November 1922, Albert Einstein is awarded the nobel prize in physics of 1921 – in absence, because the celebrated genius is on his way to Japan for a lecture series. The nobel prize committee honors his achievements in theoretical physics – especially his discovery of the photoelectric effect.

Einstein and quantum theory

Einstein thus receives a nobel prize not only for his efforts regarding relativity, but even more so for his works on the photoelectric effect, which is thought of as a milestone in the development of quantum mechanics. Quantum mechanics of all things – the odd theory that gave Einstein a headache for most of his life! In 1951, he writes to a friend: „The whole fifty years of conscious brooding have not brought me nearer to the answer to the question ‘What are light quanta?“

But the award isn’t an irony of fate, it is actually an almost accurate representation of effort. Einstein once says, he thought a hundred times more about quantum problems than he did about relativity. Despite this, he will never become a huge fan of quantum theory. Until his death he opposes the view that the statistical description that quantum theory requires marks the limit of lawfulness in nature. Instead, he thinks that quantum mechanics is incomplete, and he attacks interpretations that claim otherwise (like Niels Bohr’s Kopenhagen interpretation) with an array of thought experiments, with increasing stubbornness and yet unsuccessfully. Until his passing, he zealously works on a unified field theory, but is unable to find this coveted theory of everything.

Emigration to the USA

In the beginning of the 30s of the 20th century, the atmosphere in Berlin becomes more and more hostile and aggressive. When Adolf Hitler comes to power in 1933, Einstein and Elsa, who come from a Jewish family, emigrate to the US. Einstein resigns from the Prussian Academy of Science on his own account, before the Nazis can push him out. Henceforth, the couple lives in Princeton, New Jersey, where Einstein finds an occupation at the Institute for Advanced Studies. After Elsa’s death in 1936, his sister moves in with him. In 1940, Einstein is granted American citizenship.

Formal portrait of Albert Einstein — Albert Einstein 1935 in Princeton. Photograph by Sophie Delar (Wikimedia Commons, Public Domain)

Because of his concern that the Nazis would succeed in the construction of a nuclear bomb, and despite his pacifist attitude, Einstein signs a letter to the American president Franklin Roosevelt which recommends to engage in nuclear weapons research and build the bomb first. When nuclear bombs destroy Hiroshima and Nagasaki in 1945, Einstein must witness the consequence of the US’s successful effort. Einstein later refers to his signature as a big mistake. After the war, he promotes the peaceful use of nuclear power and nuclear disarmament. A return to Germany is off the table – the country that murdered millions of Jews is history to him. He dies in Princeton in April 1955 – leaving a scientific heritage that continues to occupy generations of physicists.

Definitioner

E = mc²

Siehe Masse-Energie-Äquivalenz.

unified field theory

Collective designation for Einstein's unsuccessful attempts to formulate a theory in which gravity and other interactions, notably electromagnetism, are described in a unified manner - a theory in which gravity and electromagnetism would be no more than different facets of one and the same underlying structure, in the same manner in which magnetism and the electrostatic force are facets of a more general description of electromagnetism.

After Einstein, quite a number of scientists have searched for a unified description of all interactions; the best-known modern incarnation of the idea of unification is string theory.

time

It is a fact of life that not all events in our universe happen concurrently - instead, there is a certain order. Defining a time coordinate or defining time, the way physicists do it, is to define a prescription to associate with each event a number so as to reflect that order - if event B happens after event A, then the number associated with B should be larger than that associated with A. The first step of this definition is to construct a clock: Choose a simple process that repeats regularly. (What is "regular"? Luckily, in our universe, all elementary processes such as a swinging pendulum, the oscillations of atoms or of electronic circuits lead to the same concept of regularity.) As a second step, install a counter: A mechanism that, with every repetition of the chosen process, raises the count by one. With this definition, one can at least assign a time (the numerical value of the counter) to events happening at location of the clock. For events at different locations, an additional definition is necessary: One needs to define simultaneity. After all, the statement that some far-away event A happens at 12 o'clock is the same as saying that event A and "our clock counter shows 12:00:00" are simultaneous. The how and why of defining simultaneity - a centre-piece of Einstein's special theory of relativity - are described in the spotlight topic Defining "now". With all these preparations, physicists can, in principle, assign a time coordinate value ("a time") to any possible events, and describes how fast or how slow processes happen, compared to that time coordinate.

theory of relativity

See relativity theory

sun

The central (and most massive) body of our solar system; the star closest to us; a ball of gas with a radius of ca. 700000 km (for comparison the radius of the earth: 12756 km) and a mass of 1.989·10³⁰ kilograms [see exponential notation]. In the interior of the sun, nuclear fusion processes run their course; they are responsible for the sun's impressive brightness.

stars (star)

A cosmic gas ball that is massive enough for pressure and temperatur in its core to reach values where self-sustained nuclear fusion reactions set in. The energy set free in these reactions makes stars into very bright sources of light and other forms of electromagnetic radiation. Once the nuclear fuel is exhausted, the star becomes a white dwarf, a neutron star or a black hole.

special theory of relativity (special relativity)

Albert Einstein's theory of the fundamentals of space, time, and movement (but not gravity). For a brief introduction, check out the chapter Special relativity of Elementary Einstein. Selected aspects of special relativity are described in the category Special relativity of our Spotlights on relativity.

space

In a strict sense: Space as we know it from everyday life: the totality of all locations in which objects can sit, with three dimensions. In a more general sense used by mathematicians, all kinds of sets of points are spaces - a line for instance, which has but a single dimension, or a two-dimensional surface, but also higher-dimensional spaces. Also, in such more general spaces, geometry can be different from the standard Euclidean geometry taught in high schools - such spaces can be curved.

theory of relativity (relativity theory)

The modern theories of space and time that go back to Albert Einstein: His special theory of relativity, which ignores the effects of gravitation, and his general theory of relativity, in which gravitation is included as a distortion of space and time. For an introduction to the basics of both theories of relativity, check out the chapters Special relativity and General relativity in Elementary Einstein.

quantum theory

The framework for formulating the physical laws that govern the world at microscopic length-scales - the physics of the micro-world, for instance of atoms, atomic nuclei or elementary particles, but also the physics of ultra-precise measurements such as those made by gravitational wave detectors.

The laws of quantum theory are fundamentally different from our everyday experience and from those of classical physics.

The first unusual feature is that, in many cases, quantum theory merely allows statements about probabilities. For instance, in classical physics, one can assign to every particle, at every point in time, a location and a velocity. Whosoever can measure those quantities precisely can, in principle, predict where the particle in question can be found at every point in the future. In quantum theory, all one can assign to a system of particles is an abstract quantum state from which can be derived no precise predictions, but merely the probabilities for detecting a specific particle at a given time in a given place. Whether or not one will really find the particle at that location is governed by chance.

The second unusual feature is a fundamental restriction placed on the exactness of certain measurements (Heisenberg uncertainty relation). For instance, the more precise one measures a particle's location, the less definite any statements one can make about its velocity.

The third feature is how quantum theory came by its name: A number of physical quantities in nature come in little packets, in quanta. For instance, according to quantum theory, electromagnetic radiation is made of tiny quanta of energy called photons.

Examples for quantum theories are quantum mechanics and relativistic quantum field theories such as Quantum electrodynamics or other parts of the standard model of particle physics.

quantum mechanics

In a more general sense: synonymous with quantum theory. In a more restricted sense: The quantum theory of particles moving under the influence of forces - wherein the particles are described as quantum objects, while the forces are not. An important application of quantum mechanics is the physics of the electron shells of atoms ("atomic physics", for short). Attempts to extend the quantum laws to govern the forces themselves lead to relativistic quantum field theories.

photoelectric effect (photo effect)

When light shines onto a metal, it can knock electrons out of the metal's atoms. This is the photoelectric effect, and its properties - how does the number and energy of the electrons depend on the frequency and intensity of the light? - can only be explained if one accepts that light is no mere electromagnetic wave, but somehow made up of some kind of light particles. With this postulate, Einstein, in 1905, paved the way for the later development of quantum mechanics.

molecules (molecule)

Composite object consisting of two or more atoms, bound together by electromagnetic forces.

mechanics

Branch of physics dealing with the motions of objects and how they react to forces acting on them. Depending on the framework used, there is classical mechanics, relativistic mechanics and quantum mechanics.

matter

In general relativity: All contents of spacetime that contribute to its curvature: particles, dust, gases, fluids, electromagnetic and other fields. In particle physics: All elementary particles with half-integer spin, such as electrons and quarks, as well as their composites such as protons and neutrons, in contrast with force particles.

light

Light in the strict sense of the word is electromagnetic radiation the human eye can detect, with wave-lengths between 400 and 700 nano metres. In relativity theory and in astronomy, the word is often used in a more general sense, encompassing all kinds of electromagnetic radiation. For instance, astronomers might talk about "infrared light" or "gamma light"; in this context, light in the stricter sense is referred to as "visible light". Within classical physics, the properties of light are governed by Maxwell's equations; in quantum physics, it turns out that light is a stream of energy packets called light quanta or photons. In the context of relativistic physics, light is of great interest, and for a number of reasons. First of all, the speed of light plays a central role in both special and general relativity. Also, there are a number of interesting effects in general relativity which are associated with the propagation of light, namely deflection, the Shapiro effect and the gravitational redshift.

gravity

See gravitation

gravitation

In classical physics: An action-at-a-distance force by which all bodies that possess mass attract each other (see Newtonian theory of gravity), synonym: gravitational force. In Einstein's general theory of relativity: The fact that matter that possesses mass, energy, pressure or similar properties distorts spacetime, and that this distortion in turn influences whatever matter might be present. An introduction to the basic ideas of general relativity is provided by the section General relativity of Elementary Einstein. More information about the nature of gravity in general relativity can be found in the spotlight text Gravity: From weightlessness to curvature.

gravity (gravitation)

general theory of relativity

Albert Einstein's theory of gravity; a generalization of his special theory of relativity. For information about the concepts and applications of this theory, we recommend the chapter general relativity of our introductory section Elementary Einstein. Further information about many different aspects of general relativity and its applications can be found in our section Spotlights on relativity.

field

A field describes how a physical quantity is distributed in space and time. For instance, the area where electric forces act on a test particle is subject to an electric field. Or the gravitational forces which act on the mass of a test body define a gravitational field. In general a field contains energy, occupies space and can change over time.

event

In the context of special or general relativity: Anything that is defined by a single point in time and a single point in space, i.e. something that happens at a definite time at a definite location. Synonym: spacetime point.