Alexander Friedmann's Life
 |
| Alexander Friedmann (1888-1925) |
Alexander Friedmann was born in Saint Petersburg, Russia on June 16 1888. His parents were both involved in the arts community for his father was a ballet dancer and his mother was pianist. Nevertheless Friedmann was a mathematician who studied at Saint Petersburg State University where he had studied for four years. He was known to be an exceptional student throughout both high school as well as university. While in university Friendmann also attended seminars based on modern physics, and soon after completed his master's degree through conducting research based on aeronautics, Earth's magnetic field, mechanics of liquid, and also the theoretical meteorology.
Over the course of many years, Friedmann was appointed many jobs for his various talents. In 1913 he received a position at the Aerological Observatory, where he was able to study meteorology. For the next several years he took part in several flights in airships to make meteorological observations. However, when the first world war started in 1914, he decided to participate in the Russian air force as a technical expert and a bomber pilot. Friedmann then returned to Saint Petersburg in 1920 when the Red Army took over Perm University where he had been a professor at. Here he took up many positions as a professor and a researcher at various institutes and universities.
Cosmological Works/ Einstein
 |
| Expanding universe |
In 1920, Friedmann became familiar with Albert Einsteins General Theory of Relativity, and 2 years later he had discovered the expanding universe solution to Einstein's general relativity field equations. Scientists had always viewed the universe as "static" meaning that it had always been the same size in the past and will also be the same size in the future. Einstein adjusted his field equations to match the static model of the universe in 1917 by adding the repulsive force of a cosmological constant to eqaulize the inward pull of gravity. However, five years later Friedmann published extensive solutions to Einstein's equations. The resulted in him arriving at the possibility of a dynamic universe that changes over time. In his paper he had hypothesized that the universe's radius of curvature is either one increasing steadily or increasing as a periodic function of time. His model was focused on a variable type of universe that included the stationary universe case as well. The Friedmann's equation is such that it explains the expansion of the universe. In this equation G represents the gravitational constant, R represents the universe's radius, c is the speed of light, p is the patter density of the universe while lastly k represents the curvature of the universe.
 |
| Friedmann equation |
However, since Einstein had reported in 1917 that the universe contracts instead of the universe expanding, Friedmann was quick to send his findings out. He titled it "On the curvature of Space" and sent his findings to a scientific journal called Zeitschrift fur Physik in 1922. Einstein who was focused on his equations that were well fit to the static universe was not pleased and had given great criticism. However Friedmann wrote back showing an extensive explanation of his calculations. He also requested that Einstein proof read all the calculations and then provide feedback. He also stated that if he were to find errors then his critique will be valid but if he didn't find any errors, he requested Einstein to fix his previous criticism. After looking through his letters and proof reading Friendmann's work, Einstein corrected his previous criticism of Friedmanns work, after realizing that Friedmann indeed was correct.
In 1928 Lemaitre who was also an exceptional scientist had also discovered that the universe was in fact not static but expanding - he proposed the Big Bang Theory, ultimately stating that the universe had begun as an atom.
The Three Universe Models
 |
| The universe models |
Freidmann's findings ultimately led to the fact that the universe's shape changes according to its own gravitational force. This results in three different models of the universe. The three different models arose from the speed of the initial expansion, and the amount of matter in the beginning universe.
The first model called "Closed" states that the universe will eventually stop expanding at some time in the future - this means that it will collapse in on itself. The reverse of expansion (collapse) is due to the high density and strong gravitational attraction. This arises from a positive space-time curvature. Therefore, this model explains that the univere has a limited lifetime even though it may be long, and is also termed "Big Crunch".
The second model called "Einstein - deSitter" i when the universe is geometrically flat. In this model it shows that the universe continuously expands until there is a slow decline. This is due to a space-time curvature of a negative value and the rate of gravity would ultimately slow down expansion. It is said that we are living in such a universe, and it is termed the "Big Freeze".
The third model is called "Open" model and instead of its geometry being flat its a hyperbola. This model is known as the "Big Rip" and this type of universe is known to expand infinitely. This is a result of a space-time curvature of zero, which is a result of low density and high rate of expansion - allowing for density to never surpass expansion.
However due to political issues between the United States and the Soviet Union Friedmann's findings were not accepted until Lemaitre had independently discovered it who was a Belgian astronomer.
George Gamow
 |
| George Gamow (1904 - 1968) |
Friedmann had many students, one of which was George Gamow who was a Russian American nuclear physict. This scientist provided a lot of evidence to support the Big Bang Theory. He met Friedmann while he was attending the Leningrad University. After graduation he seeked out to see if the newly formed quantum theory could also apply to the nucleus of an atom. He developed his own theory in 1928 on radioactivity due to his immense interest for the quantum theory. While Gamow was in Washington he developed the theory of the internal structure of red giant stars. From he developed two scientific theories with his colleague, one being the theory of the so-called Urca process and the other being the theory of the origin of chemical elements by process of successive neutron capture. In 1954 Gamow began his interest in the biological phenomena and published several papers based on information storage and transfer in living cells. Here is where he proposed the genetic code that is now confirmed through laboratory work. His most important work however involved his theory that described the radioactive alpha particles decay of atomic nuclei. He was most known for his popular writings on science that introduced millions of readers to concepts of relativity and atomic and nuclear physics which have been translated into numerous different languages. Due to his incredible scientific writings the UN awarded him the Kalinga Prize in 1956.
References
George Gamow. (2014). Retrieved from http://www.britannica.com/EBchecked/topic/225123/George-Gamow
Mastin, L. Alexander Friedmann. (2009). Retrieved from http://www.phsyicsoftheuniverse.com/scientists_friedmann.html
The Life and Career of George Gamow. (2013). Retrieved from http://www.phys.colorado.edu/public-outreach/distingushed-life-and-career
All pictures are from public domain.
No comments:
Post a Comment