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"George Gamow"
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Nuclear astrophysicists at war
The question of energy production in stars stimulated an entire generation of young physicists in the 1930s who came to work in this field exploring the fundamentals of quantum and nuclear physics. Their experience and methodologies were essential to the Manhattan Project, facilitating the rapid development of the atomic bomb. The experience and knowledge gained from the Manhattan Project then flowed back to nuclear astrophysics after the war and led to its further development. This paper is motivated by the question that was raised in the film Oppenheimer, which asks whether “a bomb can set the atmosphere on fire?”. Seeking an answer requires a close intellectual exchange between the physics of the atomic bomb and the physics of stellar burning; this exchange is the topic of this paper. The Manhattan program not only opened the path to the nuclear age for humans, but also triggered a lot of new questions and research directions in nuclear physics and astrophysics that still inform the ideas in these fields today.
Journal Article
Scientific modelling with diagrams
Diagrams can serve as representational models in scientific research, yet important questions remain about how they do so. I address some of these questions with a historical case study, in which diagrams were modified extensively in order to elaborate an early hypothesis of protein synthesis. The diagrams’ modelling role relied mainly on two features: diagrams were modified according to syntactic rules, which temporarily replaced physico-chemical reasoning, and diagram-to-target inferences were based on semantic interpretations. I then explore the lessons for the relative roles of syntax, semantics, external marks, and mental images, for justifying diagram-to-target inferences, and for the “artefactual approach” to scientific models.
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Making Knowledge Whole: Genres of Synthesis and Grammars of Ignorance
This essay examinesgenres of synthesis, by which I mean different modes for synthesizing the branches of knowledge through appeal to different representations (images, figures, framing devices, etc.) orienting scientific labor/research. These genres emerge simultaneously as concrete representations of the synthesis of knowledge on the one hand and organizational schemes for the achievement of that synthesis on the other. The article focuses on the synthetic work of two prolific scientists, astronomer Harlow Shapley and physicist George Gamow, attempting to give a sense of common aspects of their synthesizing visions and efforts. Extended attention is given to two central synthesizing genres operating within Gamow and Shapley’s long-standing projects, thescalarand thehistorical, demonstrating the changing importance of these schemes and their relation to historical contexts. Emphasis on their mid-century interest in “grammars of nature” allows comparison of their synthetic and historical commitments with the work of other synthetic efforts, in particular those of the Unity of Science movement. This history allows us to refine the concept of genres of synthesis further tying it to conceptions of the unknown, of popularization, and of meaning-making while at the same time providing an overview of Shapley and Gamow’s consonant network-building practices.
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Galactic Center Shadows: Beyond the Standard Model
In 2005 Zakharov et al. predicted an opportunity to reconstruct a shadow in Sgr A* with ground based or space—ground interferometer acting in mm or sub-mm band (the Millimetron was mentioned for such needs). The prediction was confirmed in May 2022 since the Event Horizon Telescope (EHT) Collaboration presented results of a shadow reconstruction for our Galactic Center (the shadow around the supermassive black hole in M87 was reconstructed in 2019). These reconstructions were based on EHT observations done in 2017. In 2005 Zakharov et al. also derived analytical expressions for shadow size as a function of charge for Reissner–Nordström metric and later these results were generalized for a tidal charge case. We discuss opportunities to evaluate parameters of alternative theories of gravity with shadow size estimates done by the EHT Collaboration, in particular, a tidal charge could be estimated from these observations. We also discuss opportunities to use Millimetron facilities for shadow reconstructions in M87* and Sgr A*. In our recent studies we discuss shadow formations for cases where naked singularities, wormholes or more exotic models substitute conventional black holes in galactic centers.
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Arno Penzias—Nobel laureate—Co-discoverer of the cosmic microwave background radiation and researcher of the chemistry of the sky
Arno Penzias and Robert Wilson in their Nobel-Prize-winning discovery detected the temperature in the outer space to be 3 kelvins. This provided decisive support for the Big Bang model of the birth of the Universe. Penzias was a refugee from Nazi Germany and his new homeland, the United States, provided an excellent education for him. His fruitful career at Bell Labs and in advising small companies combined with a keen interest in societal matters and contemporary politics.
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Physical models and embodied cognition
Philosophers have recently paid more attention to the physical aspects of scientific models. The attention is motivated by the prospect that a model’s physical features strongly affect its use and that this suggests re-thinking modelling in terms of extended or distributed cognition. This paper investigates two ways in which physical features of scientific models affect their use and it asks whether modelling is an instance of extended cognition. I approach these topics with a historical case study, in which scientists kept records not only of their findings, but also of some the mental operations that generated the findings. The case study shows how scientists can employ a physical model (in this case diagrams on paper) as an external information store, which allows alternating between mental manipulations, recording the outcome externally, and then feeding the outcome back into subsequent mental manipulations. The case study also demonstrates that a models’ physical nature allows replacing explicit reasoning with visuospatial manipulations. I argue, furthermore, that physical modelling does not need to exemplify a strong kind of extended cognition, the sort for which external features are mereological parts of cognition. It can exemplify a weaker kind, instead.
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The drama of ideas in the history of quantum gravity: Niels Bohr, Lev Landau, and Matvei Bronstein
Einstein's expression
‘Drama of Ideas’
to describe the history of fundamental physics is especially suitable for the problem of quantum gravity (QG). The problem was identified by Einstein in 1916 based on an empirico-cosmological argument that was cosmologically flawed and empirically immeasurable. In 1929, the problem was strikingly underestimated by prominent figures in quantum theory, W. Heisenberg and W. Pauli. In 1929, Bohr, basing on the puzzling results of recent nuclear experiments and theoretical quantum limitations, hypothesized that the law of conservation of energy does not hold in nuclear physics. The young Russian physicist Landau enthusiastically supported Bohr's ‘beautiful idea’ and in 1931 proposed its theoretical justification, which, however, was rejected by Bohr. In late 1932, Landau realized that Bohr's hypothesis was incompatible with Einstein's theory of gravity. This meeting of two fundamental theories prompted Matvei Bronstein to investigate the quantization of gravity in-depth. In 1935, he proposed the first physical theory of QG for the weak gravity and revealed how deep the QG problem was for strong gravity. He showed that the gravitational field at a point in space–time is in principle unobservable and concluded that a complete theory of QG would require the ‘
rejection of a Riemannian geometry
…
and perhaps also the rejection of our ordinary concepts of space and time, replacing them by some much deeper and non-evident concepts’
. Until now, despite thousands of publications on QG, the problem remains a great challenge in theoretical physics.
Journal Article
Martynas Yčas: The “Archivist” of the RNA Tie Club
Between about 1951 and the early 1960s, the basic structure of molecular biology was revealed. Central to our understanding was the unraveling of the various roles of RNA, culminating in the identification of messenger RNA (mRNA) and the deciphering of the genetic code. We know a great deal about the role of Brenner, Crick, Jacob, and Nirenberg in these discoveries, but many others played important supporting parts. One of these is a little-known scientist, Martynas Yčas, who appears in histories, generally without explanation, as the “archivist of the RNA Tie Club.” Yčas was born in Lithuania. His father helped write the Lithuanian Constitution in 1919. He studied Roman Law and served in the Lithuanian army before escaping from the Russians in 1940. The records of correspondence of Yčas with the physicist George Gamow and with Francis Crick throw some light on the genesis of our understanding of the role of mRNA. The story of the “RNA Tie Club” illustrates the difficulty in assigning credit for important discoveries and underscores the importance of a free exchange of information, even (or especially) among competitors.
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George Gamow and Ralph Alpher: a review of their cosmological collaboration as mentor and protégé 1942–1955
George Antonovich Gamow (1904–1968) and Ralph Asher Alpher (1921–2007) were associates from 1942 until 1968. In this paper, we examine an intense period of collaboration at George Washington University. Our inquiry pivots on a collection of 53 letters and postcards in the Library of Congress (LoC) that Alpher received from Gamow during his absences from Washington DC. In order to set our examination of the letters in their historical context, we present brief biographies of Gamow and Alpher, summarise the state that nuclear astrophysics had already reached by 1945, and examine the initial impact of the
αβγ
paper. We conducted detailed analysis of twenty of the LoC letters which documents successive attempts by Alpher and Gamow to address the deficiencies in their model of primordial element building by neutron-capture in the big bang. We give a detailed account of the interactions between Gamow writing from Los Alamos, New Mexico, and his two co-workers Alpher and Robert Herman in Washington DC. The correspondence brings their enthusiasm and commitment to life as they react to the advances and setbacks they encountered. Our narrative illustrates the remarkable partnership that Gamow and Alpher shared, a this was, infused with friendship and therein scientific discovery.
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