Alexander Friedmann

World War I

Friedmann fought in World War I on behalf of Imperial Russia, as an army aviator, an instructor, and eventually, under the revolutionary regime, as the head of an airplane factory.

Professorship

Friedmann in 1922 introduced the idea of an expanding universe that contained moving matter. Correspondence with Einstein suggests that Einstein was unwilling to accept the idea of an evolving Universe and worked instead to revise his equations to support the static, eternal Universe of Newton's time. In 1929 Hubble published the redshift vs distance relationship showing that all the galaxies in the neighborhood recede at a rate proportional to their distance, formalizing an observation made earlier by Carl Wilhelm Wirtz. Unaware of Friedmann's work, in 1927 Belgian astronomer Georges Lemaître independently formulated a theorem of an evolving Universe.

In June 1925 Friedmann was appointed as director of the Main Geophysical Observatory in Leningrad. In July 1925 he participated in a record-setting balloon flight, reaching an elevation of 7,400 m (24,300 ft).

Work

Friedmann's 1924 papers, including "Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes" ("On the possibility of a world with constant negative curvature of space") published by the German physics journal Zeitschrift für Physik (Vol. 21, pp. 326–332), demonstrated that he had command of all three Friedmann models describing positive, zero and negative curvature respectively, a decade before Robertson and Walker published their analysis.

This dynamic cosmological model of general relativity would come to form the standard for both the Big Bang and Steady State theories. Friedmann's work supported both theories equally, so it was not until the detection of the cosmic microwave background radiation that the Steady State theory was abandoned in favor of the current favorite Big Bang paradigm.

The classic solution of the Einstein field equations that describes a homogeneous and isotropic universe was called the Friedmann–Lemaître–Robertson–Walker metric, or FLRW, after Friedmann, Georges Lemaître, Howard P. Robertson and Arthur Geoffrey Walker, who worked on the problem in the 1920s and 30s independently of Friedmann.

In addition to general relativity, Friedmann's interests included hydrodynamics and meteorology.

Physicists George Gamow, Vladimir Fock, and Lev Vasilievich Keller were among his students.

Personal life and death

In 1911, he married Ekaterina Dorofeeva, though they later divorced. He married Natalia Malinina in 1923. They had a religious wedding ceremony, though both were far from religious. They had a son Alexander Alexandrovich Friedman (1925–1983), born after his father's death.

Friedmann died on 16 September 1925, from misdiagnosed typhoid fever. He had allegedly contracted the bacteria on return from his honeymoon in Crimea, when he ate an unwashed pear bought at a railway station.

Legacy

The Moon crater Fridman is named after him.

The Alexander Friedmann International Seminar is a periodical scientific event. The object of the meeting is to promote contact between scientists working in relativity, gravitation and cosmology, and related fields. The First Alexander Friedmann International Seminar on Gravitation and Cosmology commemorated the centenary of his birth in 1988.

During the 2022 COVID-19 protests in China, Tsinghua University students displayed Friedmann's equation as if it were a protest slogan, which was understood as an evasion of censorship by punning on the English phrase "freed man" and referring to liberalization and opening via the expansion of the universe.