P. J. E. Peebles
- Published in print:
- 2020
- Published Online:
- January 2021
- ISBN:
- 9780691196022
- eISBN:
- 9780691201665
- Item type:
- chapter
- Publisher:
- Princeton University Press
- DOI:
- 10.23943/princeton/9780691196022.003.0006
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology
This chapter studies the presence of “subliminal matter.” The presence of significant mass in subluminal matter was first suggested in the 1930s by the surprisingly large velocities of galaxies in ...
More
This chapter studies the presence of “subliminal matter.” The presence of significant mass in subluminal matter was first suggested in the 1930s by the surprisingly large velocities of galaxies in clusters of galaxies. The chapter traces the history of discovery of astronomical evidence of subluminal matter in large clusters of galaxies, in groups of a few or just two galaxies that are close enough that they seem likely to be gravitationally bound, and in individual spiral galaxies. There must be enough mass in spirals to account for the circular velocities of disk stars, and the mass rotationally supported in the disk must be large enough that gravity can form spiral arms, but this mass component cannot be so large that the spiral arms grow to destroy the observed nearly circular motions in the disk. These conditions require that most of the mass in a spiral galaxy is in a stable subluminal massive halo draped around the outskirts of the luminous parts of the galaxy.Less
This chapter studies the presence of “subliminal matter.” The presence of significant mass in subluminal matter was first suggested in the 1930s by the surprisingly large velocities of galaxies in clusters of galaxies. The chapter traces the history of discovery of astronomical evidence of subluminal matter in large clusters of galaxies, in groups of a few or just two galaxies that are close enough that they seem likely to be gravitationally bound, and in individual spiral galaxies. There must be enough mass in spirals to account for the circular velocities of disk stars, and the mass rotationally supported in the disk must be large enough that gravity can form spiral arms, but this mass component cannot be so large that the spiral arms grow to destroy the observed nearly circular motions in the disk. These conditions require that most of the mass in a spiral galaxy is in a stable subluminal massive halo draped around the outskirts of the luminous parts of the galaxy.
Bahram Mashhoon
- Published in print:
- 2017
- Published Online:
- July 2017
- ISBN:
- 9780198803805
- eISBN:
- 9780191842313
- Item type:
- chapter
- Publisher:
- Oxford University Press
- DOI:
- 10.1093/oso/9780198803805.003.0008
- Subject:
- Physics, Particle Physics / Astrophysics / Cosmology, Theoretical, Computational, and Statistical Physics
The implications of linearized NLG for the gravitational physics of the Solar System, spiral galaxies and nearby clusters of galaxies are critically examined in this chapter. In the Newtonian regime, ...
More
The implications of linearized NLG for the gravitational physics of the Solar System, spiral galaxies and nearby clusters of galaxies are critically examined in this chapter. In the Newtonian regime, NLG involves a reciprocal kernel with three length parameters. We discuss the determination of these parameters by comparing the predictions of the theory with observational data. Furthermore, the virial theorem for the Newtonian regime of NLG is derived and its consequences for nearby “isolated” astronomical systems in virial equilibrium are investigated. For such a galaxy, in particular, the galaxy’s baryonic diameter namely, the diameter of the smallest sphere that completely surrounds the baryonic system at the present time, is predicted to be larger than the basic nonlocality lengthscale, which is about 3 kpc, times the effective dark matter fraction of the galaxy.Less
The implications of linearized NLG for the gravitational physics of the Solar System, spiral galaxies and nearby clusters of galaxies are critically examined in this chapter. In the Newtonian regime, NLG involves a reciprocal kernel with three length parameters. We discuss the determination of these parameters by comparing the predictions of the theory with observational data. Furthermore, the virial theorem for the Newtonian regime of NLG is derived and its consequences for nearby “isolated” astronomical systems in virial equilibrium are investigated. For such a galaxy, in particular, the galaxy’s baryonic diameter namely, the diameter of the smallest sphere that completely surrounds the baryonic system at the present time, is predicted to be larger than the basic nonlocality lengthscale, which is about 3 kpc, times the effective dark matter fraction of the galaxy.
John Bolender
- Published in print:
- 2010
- Published Online:
- August 2013
- ISBN:
- 9780262014441
- eISBN:
- 9780262289238
- Item type:
- book
- Publisher:
- The MIT Press
- DOI:
- 10.7551/mitpress/9780262014441.001.0001
- Subject:
- Neuroscience, Research and Theory
This book proposes a new explanation for the forms of social relations. It argues that the core of social-relational cognition exhibits beauty—in the physicist’s sense of the word, associated with ...
More
This book proposes a new explanation for the forms of social relations. It argues that the core of social-relational cognition exhibits beauty—in the physicist’s sense of the word, associated with symmetry. The book describes a fundamental set of patterns in interpersonal cognition that account for the resulting structures of social life in terms of their symmetries and the breaking of those symmetries. It further describes the symmetries of the four fundamental social relations as ordered in a nested series akin to what one finds in the formation of a snowflake or spiral galaxy. Symmetry breaking organizes the neural activity generating the cognitive models which structure our social relationships. The book’s primary claim is that there exists a social pattern generator analogous to the central pattern generators associated with locomotion in many animal species. Spontaneous symmetry breaking structures the activity of the social pattern generator just as it does in central pattern generators. The book’s hypothesis that relational cognition results from self-organization is entirely novel, distinct from other theories, which describe sociality in terms of evolution or environment. It presents a picture of social-relational cognition as resembling something inorganic. In doing so, the hypothesis reveals deep connections among cognition, biology, and the inorganic world. One can go too far, the book acknowledges, in taking a solely dynamical view of the mind; the mind’s innate functional complexity must be due to natural selection. But this does not mean that every simple mental feature is the result of natural selection.Less
This book proposes a new explanation for the forms of social relations. It argues that the core of social-relational cognition exhibits beauty—in the physicist’s sense of the word, associated with symmetry. The book describes a fundamental set of patterns in interpersonal cognition that account for the resulting structures of social life in terms of their symmetries and the breaking of those symmetries. It further describes the symmetries of the four fundamental social relations as ordered in a nested series akin to what one finds in the formation of a snowflake or spiral galaxy. Symmetry breaking organizes the neural activity generating the cognitive models which structure our social relationships. The book’s primary claim is that there exists a social pattern generator analogous to the central pattern generators associated with locomotion in many animal species. Spontaneous symmetry breaking structures the activity of the social pattern generator just as it does in central pattern generators. The book’s hypothesis that relational cognition results from self-organization is entirely novel, distinct from other theories, which describe sociality in terms of evolution or environment. It presents a picture of social-relational cognition as resembling something inorganic. In doing so, the hypothesis reveals deep connections among cognition, biology, and the inorganic world. One can go too far, the book acknowledges, in taking a solely dynamical view of the mind; the mind’s innate functional complexity must be due to natural selection. But this does not mean that every simple mental feature is the result of natural selection.
