The Anthropic Argument against Infinite Past and the Eddington-Lemaitre Universe

This study in the philosophy of cosmology is a part of an ongoing effort to investigate and reassess the importance of the anthropic (Davies-Tipler) argument against cosmologies containing the past temporal infinity. Obviously, the prime targets of this argument are cosmological models stationary on sufficiently large scale, the classical steady state model of Bondi, Gold and Hoyle being the best example. Here we investigate the extension of application of this argument to infinitely old non-stationary models and discuss additional constraints necessary to be imposed on such models for the edge of the anthropic argument to be preserved. An illustrative counterexample is the classical Eddington-Lemaitre model, in the analysis of which major such constraints are presented. Consequences of such an approach for our understanding of the nature of time are briefly discussed.Comment: 7 pages, no figure

The Anthropic Principle and the Duration of the Cosmological Past

The place of an anthropic argument in the discrimination between various cosmological models is to be reconsidered following the classic criticisms of Paul C. W. Davies and Frank J. Tipler. Different versions of the anthropic argument against cosmologies involving an infinite series of past events are analyzed and applied to several instructive instances. This is not only of historical significance but presents an important topic for the future of cosmological research if some of the contemporary inflationary models, particularly Linde's chaotic inflation, turn out to be correct. Cognitive importance of the anthropic principle(s) to the issue of extraterrestrial intelligent observers is reconsidered in this light and several related problems facing cosmologies with past temporal infinities are also clearly defined. This issue is not only a clear example of the epistemological significance of the anthropic principle, but also has consequences for such diverse topics as SETI studies, epistemological status of cosmological concepts, theory of observation selection effects, and history of astronomy.Comment: 45 pages, 1 figur

On the First Anthropic Argument in Astrobiology

We consider the little-known anthropic argument of Fontenelle dealing with the nature of cometary orbits, given a year before the publication of Newton's Principia. This is particularly interesting in view of the rapid development of the recently resurgent theories of cometary catastrophism and their role in the modern astrobiological debates, for instance in the "rare Earth" hypothesis of Ward and Brownlee.Comment: 16 pages, 2 figures, submitted to "Earth, Moon, and Planets

Is Quantum Suicide Painless? On an Apparent Violation of The Principal Principle

The experimental setup of the self-referential quantum measurement, jovially known as the "quantum suicide" or the "quantum Russian roulette" is analyzed from the point of view of the Principal Principle of David Lewis. It is shown that the apparent violation of this principle--relating objective probabilities and subjective chance--in this type of thought experiment is just an illusion due to the usage of some terms and concepts ill-defined in the quantum context. We conclude that even in the case that Everett's (or some other "no-collapse") theory is a correct description of reality, we can coherently believe in equating subjective credence with objective chance in quantum-mechanical experiments. This is in agreement with results of the research on personal identity in the quantum context by Parfit and Tappenden.Comment: 9 page

Stability of the Protogalactic Clouds: I. Field Length in the Adiabatic Models

All gasdynamical models for the evolution of gaseous content of galaxies assume that cooling from the hot, virialized phase to the cold phase occured through some sort of thermal instability. Subsequent formation of colder clouds embedded in the hot, rarefied medium is a well-known process appearing in many astrophysical circumstances and environments. The characteristics of the condensed clouds depend on the relevant timescales for cloud formation and disruption due to either collisions or one of the operating instabilities. In this paper, the importance of the Kelvin-Helmholtz instability is investigated for the clouds forming in huge gaseous haloes of $L_\ast$ galaxies. Recent treatment of this problem by Kamaya (1997) is extended and a more realistic cooling function employed. Results show that the Kelvin-Helmholtz instability proceeds effectively on the same timescale whether we account for self-gravity or not. This has multiple significance, since these objects may have been seen as high-column density absorption line systems against the background QSOs, and probably represent the progenitors of the present-day globular clusters.Comment: 7 pages, 2 figures, Latex (uses psfig.sty

The total mass of the early-type galaxy NGC 4649 (M60)

In this paper we analyze the problem of the total mass and the total mass-to-light ratio of the early-type galaxy NGC 4649 (M60). We have used two independent techniques: the X-ray methodology which is based on the temperature of the X-ray halo of NGC 4649 and the tracer mass estimator (TME) which uses globular clusters (GCs) observed in this galaxy. We calculated the mass in Newtonian and MOdified Newtonian Dynamics (MOND) approaches and found that interior to 3 effective radii (Re) there is no need for large amounts of dark matter. Beyond 3Re dark matter starts to play important dynamical role. We also discuss possible reasons for the discrepancy between the estimates of the total mass based on X-rays and TME in the outer regions of NGC 4649.Comment: Accepted by Serbian Astronomical Journal, 8 pages, 1 figur