Alexander Friedmann: Unsung Hero of Modern Cosmology


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Ninety years ago, Russian matematician Alexander Friedmann raised the possibility of an expanding universe. He showed that our cosmos could have begun in a singularity — just what our current big bang theory predicts. Who was this man and why is he so little known to the general public? Let’s take a look.

Friedmann, Einstein, and the War

Russian mathematician and cosmologist Alexander Alexandrovich Friedmann. Image by Qwerk

Alexander Alexandrovich Friedmann was born in Saint Petersburg, Russia on June 16, 1888 – nine years after the birth of Albert Einstein. When Einstein published his theory of special relativity in 1905, seventeen-year-old Alexander was organizing student protests against Czar Nicholas II’s repressive government. A year later, Friedmann began his studies in mathematics at the University of St. Petersburg. He graduated in 1910.

While Einstein was completing his theory of general relativity in 1915, Friedmann was serving in the Russian air force in the midst of World War I. He was a ballistics instructor on the Austrian front and participated in several airship missions – for which he was awarded the military cross. He then served as an aeronautics instructor in Kiev.

The Russian Revolution of 1917 ended Russia’s involvement in World War I. Bitter over his participation in a seemingly meaningless war, Friedmann secured a position as a Professor at the University of Perm near the Ural Mountains. He soon found himself in the midst of a Civil War, with the Red army (Bolsheviks) and White Army (anti-communists) alternately occupying the city.

With the end of the Russian Civil War in 1920, communication with other European scientists resumed and Friedman learned of Einstein’s new theory of gravity. His interests had included meteorology, aerodynamics, mechanics, and hydrodynamics. Now Friedmann turned his prodigious mathematical skills towards solving Einstein’s notoriously difficult field equations of general relativity.

A Dynamic Universe?

Scientists at the time thought our universe was static and eternal– that it had always been the same size in the infinite past and will always be the same size in the infinite future. In 1917 Einstein adjusted his field equations to model just such a static universe. He added the repulsive force of a cosmological constant to balance the inward pull of gravity.

Per the Friedmann equations, the geometry of the universe is determined by its overall mass/energy density. If equal to the critical density, Ω0 the universe has zero curvature (flat configuration). If less than critical, the universe has negative curvature (open configuration). If greater than critical, the universe has positive curvature (closed configuration). Image credit: NASA/GSFC

Then in 1922 — the same year Stalin took over power in Russia — Alexander Friedmann published a set of remarkable solutions to Einstein’s equations. In an October 2012 article in Physics Today, Israeli mathematician Ari Belenkiy wrote that Friedmann had revealed a strange new universe – one which “can expand, contract, collapse, and might even be born in a singularity.

In other words, Friedmann raised the possibility of a dynamic universe which changes in size over time. In fact, Friedmann introduced the expression “expanding universe.” And one of his solutions modeled a cosmos which began in a singularity – an infinitesimally small point. It even had an expansion rate which increased over time, just as modern observations indicate. (see dark energy).

Einstein’s reaction? He wrote a short note in the German Physics Journal, Zeitschrift fur Physik,  calling Friedmann’s non-stationary world “suspicious.” Friedmann immediately sent the great physicist an extended letter detailing his work. Six months later, Einstein wrote in the journal:

“. . . my criticism . . . was based on an error in my calculations. I consider that Mr. Friedmann’s results are correct and shed new light.”

Per Belenkey, Einstein — still unable to accept the possibility of a dynamic universe — also wrote that “the solution has no physical meaning.” But  he deleted this remark from the galley proofs at the last minute.

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