For centuries, the universe was thought to be a fixed and immobile sphere surrounded by a finite number of stars and other celestial bodies. This notion, which was previously regarded as knowledge, pervaded the most inquiring minds. Copernicus, the magnificent scientific revolution's genius, is no exception. He saw the universe as a single solar system encircled by a star-studded sphere.?
Even Einstein discussed the static conception of the universe; after applying the general theory of relativity to the cosmos as a whole and analysing it, Einstein determined that space had a positive spatial curvature, signifying a "closed" or finite universe. In his dissertation titled "Properties of the Expanding Universe," Stephen Hawkings admits that "even Einstein, whose theory of relativity is the basis for almost all modern developments in cosmology, found it natural to suggest a static model of the universe."
But everything changed exactly a century ago in May 1922. Based on Einstein's general theory of relativity, Russian mathematician-meteorologist Alexander Friedmann wrote a paper outlining numerous alternative histories of the cosmos.?
One such scenario envisioned cosmic expansion beginning with a unique point. The cosmos expanded rather than remaining static and stable. What's more fascinating is that Freiedmann anticipated the expansion of the cosmos using a mathematical abstraction rather than physical proof.?
Throughout his life, he wondered and explored the connection between the math of spatial geometry and the motion of physical bodies. It is considered that his "deep appreciation for the synergy of abstract math and concrete physics prepared his mind to consider the notion that the universe could be expanding."?
On June 29, 1922, Friedmann's work proposing dynamic worlds, titled "On the Curvature of Space," was accepted for publication in the prestigious Zeitschrift f¨¹r Physik. His publication initiated a new paradigm in physical cosmology.
When one hears the phrase "Expansion of the Universe," images of an inflated ballon growing outwards into space come to mind. But this is not the right way to picture the expansion. This is the privileged observer's point of view, where we have a detached and complete understanding of what is going on, a view "from the outside."?
When we quantify cosmic expansion, we must do so from within, much like a fish describing the ocean as a whole.?
This is because we are trapped inside the universe. Then what is the picture we can construe of when we elicit the expansion of the universe? The checkboard imagery will be appropriate. The checkerboard represents our cosmos (it extends in all directions to infinity), while the coins represent galaxies.?
The coins (galaxies) would merely stay there if the universe was static, that is, not expanding or contracting. In an expanding cosmos, the squares would stretch and grow in all directions, carrying the coins with them. This means that each coin is separated from the others and that there is no centre of the cosmos.
Friedmann died of typhoid fever at the age of 37 in 1925, without the recognition he deserved, and he is frequently misquoted in the literature. But he died knowing that he had decoded a secret about the universe that no scientist had suspected before him.?
The Russian scientist Vladimir Soloviev said that "The new worldview presented by Friedmann has become the foundation of current cosmology."?
The Brazilian physicist Marcelo Gleiser believes that we can see the accomplishments of a truly revolutionary thinker in his work and words, and that science will validate his vision of an expanding universe in the future.?
References
Gleiser, M. (2017, May 24). What Does An Expanding Universe Really Mean? : 13.7: Cosmos And Culture. NPR. Retrieved May 22, 2022, from npr
Gleiser, M. (2022, January 19). Alexander Friedmann: a pioneer of cosmic expansion. Big Think. Retrieved May 22, 2022, from bigthink
Jones, J. (2017, October 24). Stephen Hawking's Ph.D. Thesis, ¡°Properties of Expanding Universes,¡± Open Culture. Retrieved May 22, 2022, from?openculture
Siegfried, T. (2022, May 20). A century ago, Alexander Friedmann envisioned the universe's expansion. Science News. Retrieved May 22, 2022, from?sciencenews