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Cosmology
A co-developer of the steady-state theory of the universe—an alternative to the Big Bang theory—explores his conception of the expanding universe. Hermann Bondi's historic book was among the first to present cosmology as a branch of physics in its own right, distinct from general relativity, philosophy, and logic. The author of many popular science books, Bondi excelled at explaining difficult scientific concepts in an interesting, accessible manner, and Cosmology attests to his skills.
Scientific American acclaimed this volume as "an authoritative manual, ably written and well thought out," praising its "coherent view of a lively, important and healthily controversy-ridden branch of science." The three-part treatment covers principles of cosmology, observational evidence, and cosmological theories. This edition features a new Introduction by Ian W. Roxburgh, a leading figure in cosmology.
Scientific American acclaimed this volume as "an authoritative manual, ably written and well thought out," praising its "coherent view of a lively, important and healthily controversy-ridden branch of science." The three-part treatment covers principles of cosmology, observational evidence, and cosmological theories. This edition features a new Introduction by Ian W. Roxburgh, a leading figure in cosmology.
- GenresScience
192 pages, Paperback
Published April 21, 2010
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Displaying 1 - 3 of 3 reviews
November 15, 2012
I could go on at length about the important role this little book played in the transformation of cosmology from haphazard speculation into respectable science, or the elegant mathematical way in which it links together relativistic, Newtonian, kinematic and steady-state approaches, or the pitfalls awaiting those overeager to apply Occam's Razor. But I'm afraid I'm going to ignore all these fascinating topics and just talk about page 44. Scientists generally like to pretend in their technical works that they are unemotional, dispassionate seekers after truth, and Bondi clearly believes in this traditional approach. The problem is that it doesn't always reflect reality. Here is a passage from Bondi concerning his group's well-known rivalry with Martin Ryle, contrasted with a later account from Simon Singh's 2004 book Big Bang:
Account in Bondi
Radio astronomy was first linked with cosmology when Gold (1951) opposed by Ryle (1951) suggested that the discrete sources ('radio stars') of radiation in the accessible band were extra-galactic... In 1953, Baade and Minkowski identified a prominent radio source with a faint optical image that was interpreted as two galaxies in collision.
Account in Singh
Gold always remembered the moment when Baade first approached him with the news that Cygnus A was a radio galaxy:
Well, I hope that's given you a better understanding of the reasons why most technical books don't sell...
Account in Bondi
Radio astronomy was first linked with cosmology when Gold (1951) opposed by Ryle (1951) suggested that the discrete sources ('radio stars') of radiation in the accessible band were extra-galactic... In 1953, Baade and Minkowski identified a prominent radio source with a faint optical image that was interpreted as two galaxies in collision.
Account in Singh
Gold always remembered the moment when Baade first approached him with the news that Cygnus A was a radio galaxy:
In the huge antechamber to the conference room one was milling around like one usually does, and Walter Baade was there. He said, 'Tommy! Come over here! Look what we've got!'... Then Ryle comes into the room. Baade shouts, 'Martin! Come over here! Have a look at what we've found!' Ryle comes and looks with a very stern face at the photographs, does not say a word, throws himself on a nearby couch - face down, buried in his hands - and weeps.
Well, I hope that's given you a better understanding of the reasons why most technical books don't sell...
March 3, 2024
Read this - my third Bondi book - as another attempt to understand the steady-state cosmological theory (Bondi and Gold, 1948; Hoyle, the third proponent, had a slightly different perspective). As with the other Bondi books, I’m not at all sure that I understand, in an overarching way, his theory.
Bondi works from a deductive cosmological principle,* in contrast to Newton and Einstein's inductive approach (theory drawn from empirical data), though Bondi states outright that “most of the workers in the field adopt an intermediate position combining parts of both.” The steady-state cosmological model is a moving outward of energy (per Hubble’s findings), with energy from stars filling in from behind: “The average density of radiation…is replenished by the action of matter in stars which constantly generates fresh radiation.” While, overall, the universe presents the same aspect (homogeneity of outward, dissipated energy), there are local irregularities due to gravity (stars within galaxies) effects. These, in turn, provide new concentrations of energy that radiate outward. This overall homogeneity of the universe is Bondi’s cosmological principle: “The universe as a whole exhibits “a splendid symmetry,” he states, “so that on a large scale it “is homogenous.”**
The steady-state model might be clearer when contrasted with the relativistic cosmology of Einstein. For Einstein, the steady state is an equilibrium point between outward expansion via radiation and the inward movement toward a gravitational center via the attractive force of gravity. Such an equilibrium state is, according to Bondi, citing others, inherently unstable as a tap in one direction or the other (outward or inward) would be enough to send the universe either into either a heat death or a big crunch scenario, contracting to its pre big bang singularity state. In Bondi’s account, the equilibrium point is dynamic: outgoing, dissipating energy is constantly replenished by, as it were, infilling from behind.
Left there, the Bondi model seems problematic for two reasons. First, by implication the outward movement of radiated energy seems to continue in perpetuity, i.e., released from gravitational effects, radiated energy continues its inherent inertial motion, infinitely. But that is at odds with various Bondi references to a spherical cosmos. What causes that? Bondi is surprisingly sparse on the role of gravity in pulling the cosmos into a spherical shape. Also, Bondi states that stars create new sources of radiated energy and matter, but what doesn’t get explained is how, in a dissipating universe, new galactic structures and stars form as, presumably, dissipation disperses matter (gas and dust), thereby, separating gravity’s attractive effects and preventing new star formation.
Are these two points connected? Radiated energy’s movement around a sphere returns to its originating point, allowing the progressive concentration of matter that, in turn, forms per Bondi’s theory new sources of radiated energy? What Bondi does not seem to address is, implication wise, the significance of an overall spherical cosmos. Specifically, could the three dominant scenarios for the cosmos may all be wrapped up in one package? A big bang scenario creates radiated energy - movement outward, at ever expanding speeds, per Hubble’s findings, as it is progressively released from gravitational effects per Newton’s inverse square law. At some point in space and time, there is the static equilibrium that Einstein saw, a perfect balance between outward radiated movement and inward gravitational pull. But that equilibrium point can only be momentary as radiated energy continues with its inertial straight-line movement in the presence of curvature. This then increasingly becomes subject to gravitational effects as it moves toward the cosmic gravitational center that now results in a new Big Bang scenario. And this outward-stasis-inward movement continues, cyclically and perpetually.
Also, in Bondi’s model, as radiated energy moves away from gravitational mass, it frees itself from gravity’s effects so that inertial motion continues, free of gravitational attraction. There’s no pulling involved by dark matter or dark energy. Free is, simply, a release from gravity that allows matter and energy to do its thing - movement with speed, free of gravity (until it comes within a gravitational field again, in a spherical cosmos).
*Homogeneity results from the steady, outward flow of dissipating energy. The deductive approach that Bondi uses is how to account for this overall “evenness” in the presence of energy. He does this by saying that new sources of energy fill in from behind that radiate outward and, in time, dissipate into a state of evenness.
**From Google, the Bondi-Gold theorem “holds that the universe is constantly expanding but matter is constantly created to form new stars and galaxies to maintain a constant average density.” For more, see their original paper:
https://www.sophiararebooks.com/pages....
Bondi works from a deductive cosmological principle,* in contrast to Newton and Einstein's inductive approach (theory drawn from empirical data), though Bondi states outright that “most of the workers in the field adopt an intermediate position combining parts of both.” The steady-state cosmological model is a moving outward of energy (per Hubble’s findings), with energy from stars filling in from behind: “The average density of radiation…is replenished by the action of matter in stars which constantly generates fresh radiation.” While, overall, the universe presents the same aspect (homogeneity of outward, dissipated energy), there are local irregularities due to gravity (stars within galaxies) effects. These, in turn, provide new concentrations of energy that radiate outward. This overall homogeneity of the universe is Bondi’s cosmological principle: “The universe as a whole exhibits “a splendid symmetry,” he states, “so that on a large scale it “is homogenous.”**
The steady-state model might be clearer when contrasted with the relativistic cosmology of Einstein. For Einstein, the steady state is an equilibrium point between outward expansion via radiation and the inward movement toward a gravitational center via the attractive force of gravity. Such an equilibrium state is, according to Bondi, citing others, inherently unstable as a tap in one direction or the other (outward or inward) would be enough to send the universe either into either a heat death or a big crunch scenario, contracting to its pre big bang singularity state. In Bondi’s account, the equilibrium point is dynamic: outgoing, dissipating energy is constantly replenished by, as it were, infilling from behind.
Left there, the Bondi model seems problematic for two reasons. First, by implication the outward movement of radiated energy seems to continue in perpetuity, i.e., released from gravitational effects, radiated energy continues its inherent inertial motion, infinitely. But that is at odds with various Bondi references to a spherical cosmos. What causes that? Bondi is surprisingly sparse on the role of gravity in pulling the cosmos into a spherical shape. Also, Bondi states that stars create new sources of radiated energy and matter, but what doesn’t get explained is how, in a dissipating universe, new galactic structures and stars form as, presumably, dissipation disperses matter (gas and dust), thereby, separating gravity’s attractive effects and preventing new star formation.
Are these two points connected? Radiated energy’s movement around a sphere returns to its originating point, allowing the progressive concentration of matter that, in turn, forms per Bondi’s theory new sources of radiated energy? What Bondi does not seem to address is, implication wise, the significance of an overall spherical cosmos. Specifically, could the three dominant scenarios for the cosmos may all be wrapped up in one package? A big bang scenario creates radiated energy - movement outward, at ever expanding speeds, per Hubble’s findings, as it is progressively released from gravitational effects per Newton’s inverse square law. At some point in space and time, there is the static equilibrium that Einstein saw, a perfect balance between outward radiated movement and inward gravitational pull. But that equilibrium point can only be momentary as radiated energy continues with its inertial straight-line movement in the presence of curvature. This then increasingly becomes subject to gravitational effects as it moves toward the cosmic gravitational center that now results in a new Big Bang scenario. And this outward-stasis-inward movement continues, cyclically and perpetually.
Also, in Bondi’s model, as radiated energy moves away from gravitational mass, it frees itself from gravity’s effects so that inertial motion continues, free of gravitational attraction. There’s no pulling involved by dark matter or dark energy. Free is, simply, a release from gravity that allows matter and energy to do its thing - movement with speed, free of gravity (until it comes within a gravitational field again, in a spherical cosmos).
*Homogeneity results from the steady, outward flow of dissipating energy. The deductive approach that Bondi uses is how to account for this overall “evenness” in the presence of energy. He does this by saying that new sources of energy fill in from behind that radiate outward and, in time, dissipate into a state of evenness.
**From Google, the Bondi-Gold theorem “holds that the universe is constantly expanding but matter is constantly created to form new stars and galaxies to maintain a constant average density.” For more, see their original paper:
https://www.sophiararebooks.com/pages....
December 25, 2014
A beautiful but very aged introduction to cosmology. Worth reading for the philosphical take on it, and to get an understanding of how the theory developed. However, many of the theories discussed in this book have been discarded by now, and of course the more recent discoveries in cosmology are not in there.
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