Tag Archives: Alexander Friedmann

Alexander Friedmann and the Big Bang : A scientific revolution

The following is an excerpt from Chapter 4 and 5 of the book  The Big Bang Revolutionaries: The Untold Story of Three Scientists Who Reenchanted Cosmology, by Jean-Pierre Luminet.

The book has received rave reviews including from three Nobel Prize winners.

****

In 1922, Alexander Friedmann took the step that Albert Einstein had not been ready to take: if one abandons the hypothesis of a static universe, the relativistic cosmological problem comprises an infinite number of solutions in which the metric varies as a function of time. Friedmann wrote:

Thus begins this founding notice of non-static cosmology. Received on June 29, 1922, by the German journal Zeitschrift für Physik, it was published shortly afterwards.

Ahead of Its Time

Friedmann’s article was ahead of its time, as one can also see from the fact that anybody studying modern cosmology can immediately recognize its main equations. While the formulations of the various metrics (de Sitter’s as well as Friedmann’s) would later change to the unified form of Howard Robertson and Arthur Walker, the differential equations that govern the time development of a space of constant positive curvature have not changed one iota.

With his 1922 article, Friedmann introduced a scientific revolution of the same magnitude as the Copernican revolution. In pre-Copernican cosmology, space was centered on a very particular place, the Earth. In pre-Friedmannian cosmology, the universe was static, in the sense of not evolving. Friedmannian cosmology introduces the historicity of the universe as space-time, as well as the idea of a beginning.

His second major cosmological article appeared in 1924. In 1925, he was appointed director of the Leningrad Geophysical Institute. In the summer of 1925, in the company of the aviator P. F. Fedosenko, he beat the altitude record in a stratospheric balloon, rising to 7,400 meters.

Friedmann died suddenly in Leningrad on September 16, 1925, from typhoid fever, at the age of thirty-seven. In 1931, he was posthumously awarded the Lenin Prize for his outstanding scientific work.

In Search of a Lost Tomb

Friedmann is buried in his hometown. An instructive anecdote is worth telling. The location of the Russian scientist’s grave was quickly forgotten, especially since the Stalinist regime that followed was hardly inclined to perpetuate the memory of this renowned “creationist” scientist. In 1988, the Alexander Friedmann Laboratory of the University of St. Petersburg (then called Leningrad State University) decided to organize the first “A. Friedmann International Seminar in Cosmology” to honor the centenary of the scientist’s birth. The director of the Friedmann Institute, my friend Andrey Grib, had the idea of a search for Friedmann’s tomb, planning a small commemorative ceremony in which admirers from various countries would participate. A venerable professor at the Institute of Physics and Technology in St. Petersburg and a former PhD student of Friedmann, Georgy Grinberg, remembered having attended the funeral of the scientist at the Smolenskoye Cemetery, and that the cosmologist’s grave was close to that of the great mathematician Leonhard Euler.

Grib therefore asked one of his students, Mihail Rosenberg, to go to the cemetery to locate the tomb — even hinting that this task would be recognized as part of his thesis work. When Rosenberg went to the cemetery and asked to consult the register of all the people buried here, the authorities replied that they had no information from prior to World War II. Rosenberg then asked to see the tomb of Leonhard Euler. After the war, he was told, Euler’s remains were transferred to another cemetery. There remained at least the old location, which the authorities indicated to him. Rosenberg explored the surroundings but found no evidence of Friedmann’s presence. He then began to quarrel with the authorities: How can the records have disappeared? At this point, an attendant approached and inquired about the dispute. The director of the cemetery replied that the student was looking for a certain “Friedmann.” “Which Friedmann,” asked the employee, “the one who discovered the non-static cosmological solution to Einstein’s equations?”

“Yes, yes,” exclaimed the student.

“Well, come with me, I’ll show you!”

This is how the cosmologist’s grave was discovered. The cemetery employee was none other than a former physicist who’d had to leave his research institute for lack of funds.

****

Jean-Pierre Luminet, a French astrophysicist specializing in black holes and cosmology, is emeritus research director at the French National Centre for Scientific Research. He is a member of the Laboratoire d’Astrophysique de Marseille (LAM) and Laboratoire Univers et Théories (LUTH) of the Paris-Meudon Observatory. Luminet has been awarded several prizes. These include the Georges Lemaître Prize (1999) for his work in cosmology, the UNESCO Kalinga Prize (2021), and the Einstein medal for the Popularization of Science (2021). He has published more than twenty science books, eight historical novels, and eight poetry collections. The asteroid 5523 Luminet was named in his honor.

A brief history of space (4/4)

Sequel of the preceding post A Brief History of Space (3/4) : From Descartes to Schwarzschild

Cosmology developed rapidly after the completion of general relativity by Albert Einstein, in 1915. In this theory, the Universe does not reduce to a space and a time which are absolute and separate; it is made up of the union of space and time into a four dimensional geometry, which is curved by the presence of matter.

Albert Einstein (here in 1910) developed the theory of relativity and was awarded the 1921 Nobel prize for physics. Image by © Hulton-Deutsch, Collection/CORBIS

It is in fact the curvature of space-time as a whole which allows one to correctly model gravity, and not only the curvature of space, such as Clifford had hoped. The non-Euclidean character of the Universe appeared from then on not as a strangeness, but on the contrary as a physical necessity for taking account of gravitational effects. The curvature is connected to the density of matter. In 1917, Einstein presented the first relativistic model for the universe. Like Riemann, he wanted a closed universe (one whose volume and circumference were perfectly finite and measurable) without a boundary; he also chose the hypersphere to model the spatial part of the Universe.

Einstein static universe in a space-time diagram.

At any rate, Einstein’s model made the hypothesis of a static Universe, with the radius of the hypersphere remaining invariable over the course of time. In truth, the cosmological solutions of relativity allow complete freedom for one to imagine a space which expands or contracts over the course of time: this was demonstrated by the Russian theorist Alexander Friedmann, between 1922 and 1924.

At the same time, the installment of the large telescope at Mount Wilson, in the United States, allowed for a radical change in the cosmic landscape. In 1924, the observations of Edwin Hubble proved that the nebula NGC 6822 was situated far beyond our galaxy. Very rapidly, Hubble and his collaborators showed that this was the case for all of the spiral nebulae, including our famous neighbor, the Andromeda nebula: these are galaxies in their own right, and the Universe is made up of the ensemble of these galaxies. The “island-universes” already envisaged by Thomas Wright, Kant and Johann Heinrich Lambert were legitimized by experiment, and the physical Universe seemed suddenly to be immensely enlarged, passing from a few thousand to several dozen million light-years at the minimum. Beyond this spatial enlargement, the second major discovery concerned the time evolution of the Universe. In 1925, indications accumulated which tended to lead one to believe that other galaxies were systematically moving away from ours, with speeds which were proportional to their distance. Continue reading