Niels Bohr
Niels Henrik David Bohr (Copenhagen, October 7, 1885-Copenhagen, November 18, 1962) was a Danish physicist who contributed to the understanding of the atom and quantum mechanics. He was awarded the Nobel Prize in Physics in 1922.
Biography
Any phrase I make will be considered by you not as an assertion, but as a question.(Words with which Niels Bohr used to start his seminars)
He was born in Copenhagen, the son of Christian Bohr, a devout Lutheran and professor of physiology at the city's university, and Ellen Adler, a member of a wealthy Jewish family of great importance in Danish banking and "Parliamentary" circles. ». After receiving his doctorate from the University of Copenhagen in 1911, and attempting further studies at the Cavendish Laboratory in Cambridge with the physicist Joseph John Thomson, discoverer of the electron (the subject of Bohr's doctoral thesis) and Nobel Prize winner in 1906, who did not show great interest in the young Bohr, he completed his studies in Manchester, with Ernest Rutherford as a teacher, with whom he established a lasting scientific and friendly relationship.
In 1916, Niels Bohr began working as a professor of theoretical physics at the University of Copenhagen, raising funds to create the Nordic Institute for Theoretical Physics, which he directed from 1920 until his death.
In 1943, with World War II raging, Bohr escaped to Sweden to avoid arrest by German police, later traveling to London. Once safe, he supported Anglo-American attempts to develop atomic weapons, believing that the German bomb was imminent, and worked for the Manhattan Project in Los Alamos, New Mexico (USA).
After the war, advocating for the peaceful uses of nuclear energy, he returned to Copenhagen, where he lived until his death in 1962.
His younger brother, Harald Bohr, was also a renowned mathematician as well as an Olympic soccer player, and the two brothers played together for Akademisk Boldklub, where Niels Bohr was goalkeeper.
Niels's son, Aage Niels Bohr, trained at the institute run by his father, replaced him as director, and also won the Nobel Prize in Physics in 1975.
Scientific research
Based on the theories of Ernest Rutherford (Rutherford's atom) he published his own atomic model (Bohr's atomic model) in 1913, introducing the theory of quantized orbits, which in quantum mechanical theory consists of the characteristics that, in Around the atomic nucleus, the number of electrons in each orbit increases from the inside to the outside.
In his model, in addition, the electrons could fall (pass from one orbit to another) from an outer orbital to an inner one, emitting a photon of discrete energy, a fact on which the quantum mechanics.
In 1922, he received the Nobel Prize in Physics for his work on atomic structure and radiation. Numerous physicists, based on this principle, concluded that light had a wave-particle duality showing mutually exclusive properties depending on the case.
In 1933 Bohr proposed the liquid drop hypothesis, a theory that allowed us to explain nuclear disintegrations and specifically the great fission capacity of the uranium 235 isotope.
Debates with Einstein
For this new quantum principle, Bohr also found philosophical implications that served as justification. However, the new conceptualism of reality in quantum physics (Bohr, Max Born and others) does not It was shared by Albert Einstein, whose criteria was closer to the rationalism of classical mechanics, without ruling out empirical physical phenomena of any nature. His critical phrases directed at the then “upstart” quantum mechanics are famous:
«God does not play dice with the Universe» (...) «I like to think that the Moon is still there, even if it does not look at it» (...) «this is a creepy action away» (...)
- Einstein was reluctant to interpret physical, philosophical and theological that Bohr derived from the principles of the new mechanics, and certain aspects inherent in quantum mechanicswhich evoke or suggest that the orderly matter is derived from an underlying prior state in which the matter is in permanent disorder or governed by chance (thesis that, on the other hand, already proposed at the time the presocratic philosopher Democrito, precisely the creator of the term atom atom) and that on this scale only follows laws of probability, which would lead to thinking that the whole universe is based on chance from its atomic or subatomic level.
- The second sentence alludes to the fact that the state or behavior of the matter is the direct consequence of the mere fact of observing it. The latter gave rise to the famous paradox of Schrödinger's cat, according to which the animal, introduced into a box and whose life depends on the movement of a quantumI'd be alive and dead at the same timeuntil an observer opened the box, when decide the luck or state of the feline.
- The latter, related to the previous one, refers to the phenomenon entitled “ghost action at distance”, a critique that was made about the reality of the concept of quantum interlacing; to argue its discrepancy, he proposed another logical experiment that could be titled Einstein's default pairsor "a pair of gloves."
To all this, Bohr is said to have responded:
"Stop telling God how to use his dice. »
Bohr's indeterminable pairs vs. Einstein's predetermined pairs
Two observers (Bohr and Einstein) accept the latter's logical-experimental proposition as a valid analogy to settle their different criteria. An assistant (packer) goes into an adjoining room, takes a pair of gloves and packs them separately, one in each pack, so the packer determines, and is the only one who knows with certainty which glove is in each package. He next passes into a second adjoining room, and hands both packages over to another attendant, whose task it is to mail one of them to the North Pole; This second helper, like the observers, also does not know which package each glove is in, introducing his circumstantial indeterminism or probability factor into the experiment. Once this is done, this helper or (sender) delivers the packet that he has not sent , to the observers of the first room.
They open it, observe and verify that it is the left glove:
- Einstein exclaims:
The glove that has been sent to the north pole is the right, we know it instantly and the glove was already, always was, the right, because this was already or had been predetermined by the Packaging.
- But Bohr concludes:
The glove was in an undeterminable and undeterminable state until we opened the package, because until that deterministic moment, we had no certainty and existed, mathematically, 50% probability that it was the right or the left, only when we opened it we had that certainty, ergo until then it was “right and left at the same time” because it was in a state of “equal probability” established by the sender that is really who has made the last decision and that we now observe.
Actually, Bohr's concept that "was right and left at the same time," means that if we have to take into account the fact that it is right or left for something important (like to make a mathematical calculation), as long as we have not opened the box, we must consider 50% the possibility that it is left and 50% that it is right, in order to make the correct calculation, and this is especially important if it will never be possible for us open the box and determine which one it was.
Extrapolation of Bohr's criteria against Einstein's to quantum physics
Bohr held a debate with Einstein regarding the validity or invalidity of the laws of Relativity in the subatomic world of Quantum Physics. Einstein said that the material universe was "local and real," where the local meant that nothing can exceed the speed of light, while the real meant that things exist in a single defined form in a determined time and space. Bohr for his part appealed to the & # 34; wave function & # 34; of subatomic particles and the state of "superposition" who can present these For example, two electrons could be in two opposite and extremely distant states at the same time and what happens with one at a certain point in the universe is experienced by the other at the other end of the universe. This could be the product of one of two alternatives: a) subatomic particles at two distant points in the universe send each other information about their states at speeds greater than that of light, with which the superposition would be explained by the presence of more than one electron that communicate at different points in the universe (this explanation did not attempt to make things real, but did not allow them to be local, since there would be a speed of communication greater than that of light). The other alternative told us: b) subatomic particles can exist in two or more states at the same time. These are maintained in the form of probabilities of manifestation in precise states, but they do not manifest in one of these until the moment they are the object of a determined stimulus: observation, and it is only after the act of observation that we find the particle at a specific coordinate of space and time. Here what is being attempted is reality itself, or the fact that in the subatomic world things are real and appear in a specific state in a precise time-space. In summary, the position of Bohr and of Quantum Physics is that in the subatomic world, things cannot be real and local at the same time.
It was during the development of this debate that Einstein used the famous phrase: "God does not play dice". There are reliable records of said phrase, which does not occur with an alleged counterargument by Bohr to Einstein in the same debate, according to which he said: "Einstein, stop telling God what to do with his dice!" #3. 4;.
Forced exile
One of Bohr's most famous students was Werner Heisenberg, who became leader of the German atomic bomb project. When the Nazi occupation of Denmark began, Bohr, who had been baptized into the Christian Church, remained there despite the fact that his mother was Jewish. In 1941 Bohr received a visit from Heisenberg in Copenhagen, however he did not understand his position; Heisenberg and most German physicists were in favor of preventing the production of the atomic bomb for military use, although they wanted to investigate the possibilities of nuclear technology.
The play Copenhagen, written by Michael Frayn and performed for a time on Broadway, was about what might have happened in the meeting between Bohr and Heisenberg in 1941. In 2002 the film version of the play appeared. book, directed by Howard Davies.
In September 1943, to avoid arrest by the German police, Bohr was forced to go to Sweden, from where he traveled the following month to London, finally heading to the United States in December. There he participated in the construction of the first atomic bombs. He returned to Denmark in 1945.
After the war, he became a passionate advocate of nuclear disarmament. He gave the Gifford Lectures, in the 1948-1950 academic years, on the topic Causality and Complementarity . In 1952, Bohr helped create the European Center for Nuclear Research (CERN) in Geneva, Switzerland. In 1955, he organized the first Atoms for Peace Conference in Geneva.
Work and acknowledgments
He was the author of several popular and reflective books, including Theory of Spectres and Atomic Constitution (1922), Light and Life (1933), Atomic Theory and Description of Nature (1934), The Mechanism of Nuclear Fission (1939) and Atomic Physics and Human Knowledge (1958). In 1970 the editorial Aguilar published in Spanish the compilation New essays on atomic physics and human knowledge 1958-1962.
Bohr was awarded the 1922 Nobel Prize in Physics for his work on atomic structure and radiation, and the 1926 Franklin Medal for Physics. He was also the first to receive, in 1958, the Atoms for Peace award.
The Bohr crater on the moon is named after him. Similarly, the chemical element bohrium was named after him, as was the asteroid (3948) Bohr discovered by Poul Jensen on September 15, 1985.
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