Discoverer of Expanding Universe

Life of Alexander Friedmann

Figure 1: A picture of Alexander Friedmann (1)

Alexander Friedmann (1888 - 1925) was a scientist born on June 16, 1888 in Saint Petersburg, Russia (1). He wasan excellent scholar in his high school at Second Saint Petersburg Gymnasium and at Saint Petersburg State University where he pursed his study in Mathematics from 1906 to 1910 (1). He learnt about quantum theory, relativity and statistical mechanics from seminars by Vienna- born Paul Ehrenfest in the same university (1). 

Like most scientists in the early modern physics era, Friedmann also researched on different topics like fluid dynamics, meteorology and electro-magnetism. In 1913, He started studying meteorology in the Aerological Observatory in a suburb of Saint Petersburg (1).  Following that year, he got in to aeronautics in Leipzig where he started taking part in flights in airships to make meteorological observations, and later volunteered to partake with the Russian Air Force as a technical expert and pilot  in the First World War (1). During this period, he taught aerodynamics to pilots and in 1916, the became the head of the Central Aeronautical Station in Kiev (1). In 1920, Friedmann returned to Saint Petersburg due to political conditions in Moscow, to the Main Geophysical Observatory (1). As a professor in Petrograd University, he taught mechanics, physics and mathematics while researching in Railway Engineering, Naval Academy and Optical Institute (1). Few weeks before his death from typhus in September 1925, Friedmann made a risky record-breaking balloon flight to collect data in high altitude (2).

Contributions to Cosmology

Alexander Friedmann studied Albert Einstein's papers on General Theory of Relativity and in 1922, he discovered a solution to Einstein's equations describing the expanding universe (1).  It was the birth of the theory of the formation of our universe, Big Bang. His solutions that describe the evolution of our Universe was initially strongly resisted. His equations named, the "Friedmann equations" set a framework for describing Cosmology using General Relativity, the evolution of a perfect-fluid cosmon of uniform mass density (2).  Friedmann and Frederiks put together a mathematical introduction to tensor calculus and General Relativity and Friedmann himself introduced the fundamental idea of modern cosmology, and the possibility that our Universe could have originated from a singularity in two Zeitschrift fur Physik papers (2). 

Figure 2: Three Possible Scenarios described by Friedmann on the evolution of our universe with t0 referring to the current time (2) 

Alexander Friedmann came up three possible scenarios for the fate of our Cosmological Universe as shown by the three curves on the plot in Figure 2. The curve M1 is the scenario where our Universe started with a singularity, with a short decelerating rate of expansion followed by the current accelerated expansion; the curve M2 shows a scenario where our Universe started with a finite radius and since then has been expanding at an accelerated pace. The curve referred to as P shows a scenario where our Universe will in the future stop expanding and contract back to a point of singularity and he found the period of this universe to be 100 billion years (2).

Einstein and Friedmann

Friedmann used papers written by Einstein and de Sitter (Two people who had given solutions the General Relativity equation) to give a wider perspective than either of them on the interpretation of General Relativity with Riemannian geometry (2). At present, we use Friedmann's first order differential equation  to describe the dynamics of the "3-D hypersphere" Universe of ours (2). However, in 1922 when Friedmann published his papers on these ideas, Einstein was not welcoming about his main ideas (2). Einstein had believed in a static Universe that always existed while Friedmann's theory was the idea of singularity and the expanding Universe. Einstein showed his reaction by suggesting a mathematical error in Friedmann's derivation of his equations and that the equations were approximations (2). Responding to Einstein, Friedmann wrote a long letter explaining his derivation and Einstein had published another note on the correctness of Friedmann's derivation and eight years later Einstein accepted the idea of the expanding Universe by looking at the observations made by Edwin Hubble of distant galaxies (2). 

Figure 3: Scientists who worked on expansion theory of Universe and also convinced Einstein of a  non-static evolution of our Universe (3)

George Gamow (1904 - 1968) born in Ukraine was a US-based physicist (4). He attended Leningrad University at Saint Petersburg where he was a student of Alexander Friedmann (5). He helped Friedmann with calculations in his theories, however he himself worked on developing quantum theory of radioactivity and successfully first explained the theory behind the decay of radioactive elements (5). He later continued his work on theoretical nuclear physics at the Copenhagen Institute of Theoretical Physics as a fellow (5). 

Friedmann's 1923 book about the theory behind the size of our cosmos has been largely unknown, and it sad that some of his misquoted papers are his "established" work (2). In a bigger perspective, his contributions to our little understanding of the dynamics of our universe has been outstanding. Research in 1998 by teams led by laureates - Saul Perlmutter, Adam Riess and Brian Schmidt revealed the accelerated expanding universe was worthy of the 2011 Nobel Prize (2).

Interesting Fact: "Friedmann and Tamarkin were student leaders of strikes at the school in protest at the government's repressive measures against schools." (6)

References

(1) http://www.physicsoftheuniverse.com/scientists_friedmann.html

(2) Phys. Today 65(10), 38 (2012), A. Belenkiy; doi: 10.1063/PT.3.1750
(3) http://legrandunivers.blogspot.ca/2014/03/le-destin-de-lunivers.html
(4) http://www.atnf.csiro.au/outreach/education/senior/cosmicengine/hubble.html
(5) http://www.britannica.com/EBchecked/topic/225123/George-Gamow
(6) http://www-history.mcs.st-and.ac.uk/Biographies/Friedmann.html