Alternative Explanations of the Cosmic Microwave Background: A Historical and an Epistemological Perspective

📝 Abstract

We historically trace various non-conventional explanations for the origin of the cosmic microwave background and discuss their merit, while analyzing the dynamics of their rejection, as well as the relevant physical and methodological reasons for it. It turns out that there have been many such unorthodox interpretations; not only those developed in the context of theories rejecting the relativistic (“Big Bang”) paradigm entirely (e.g., by Alfven, Hoyle and Narlikar) but also those coming from the camp of original thinkers firmly entrenched in the relativistic milieu (e.g., by Rees, Ellis, Rowan-Robinson, Layzer and Hively). In fact, the orthodox interpretation has only incrementally won out against the alternatives over the course of the three decades of its multi-stage development. While on the whole, none of the alternatives to the hot Big Bang scenario is persuasive today, we discuss the epistemic ramifications of establishing orthodoxy and eliminating alternatives in science, an issue recently discussed by philosophers and historians of science for other areas of physics. Finally, we single out some plausible and possibly fruitful ideas offered by the alternatives.

💡 Analysis

We historically trace various non-conventional explanations for the origin of the cosmic microwave background and discuss their merit, while analyzing the dynamics of their rejection, as well as the relevant physical and methodological reasons for it. It turns out that there have been many such unorthodox interpretations; not only those developed in the context of theories rejecting the relativistic (“Big Bang”) paradigm entirely (e.g., by Alfven, Hoyle and Narlikar) but also those coming from the camp of original thinkers firmly entrenched in the relativistic milieu (e.g., by Rees, Ellis, Rowan-Robinson, Layzer and Hively). In fact, the orthodox interpretation has only incrementally won out against the alternatives over the course of the three decades of its multi-stage development. While on the whole, none of the alternatives to the hot Big Bang scenario is persuasive today, we discuss the epistemic ramifications of establishing orthodoxy and eliminating alternatives in science, an issue recently discussed by philosophers and historians of science for other areas of physics. Finally, we single out some plausible and possibly fruitful ideas offered by the alternatives.

📄 Content

Preprint - To appear in The Studies in History and Philosophy of Modern Physics

Milan M. Ćirković Astronomical Observatory Belgrade, Serbia

Slobodan Perović Department of Philosophy University of Belgrade Serbia

ALTERNATIVE EXPLANATIONS OF THE COSMIC MICROWAVE BACKGROUND: A HISTORICAL AND AN EPISTEMOLOGICAL PERSPECTIVE

Abstract: We historically trace various non-conventional explanations for the origin of the cosmic microwave background and discuss their merit, while analyzing the dynamics of their rejection, as well as the relevant physical and methodological reasons for it. It turns out that there have been many such unorthodox interpretations; not only those developed in the context of theories rejecting the relativistic (“Big Bang”) paradigm entirely (e.g., by Alfvén, Hoyle and Narlikar) but also those coming from the camp of original thinkers firmly entrenched in the relativistic milieu (e.g., by Rees, Ellis, Rowan-Robinson, Layzer and Hively). In fact, the orthodox interpretation has only incrementally won out against the alternatives over the course of the three decades of its multi-stage development. While on the whole, none of the alternatives to the hot Big Bang scenario is persuasive today, we discuss the epistemic ramifications of establishing orthodoxy and eliminating alternatives in science, an issue recently discussed by philosophers and historians of science for other areas of physics. Finally, we single out some plausible and possibly fruitful ideas offered by the alternatives.

Keywords: astrophysics; cosmology; cosmic microwave background; history of astronomy; falsificationism; theory change; evidence

ALTERNATIVE EXPLANATIONS OF THE COSMIC MICROWAVE BACKGROUND

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1. Introduction The discovery of the cosmic microwave background (CMB) in 1965 by Arno Penzias and Robert Wilson and interpreted by Robert H. Dicke and his co-workers was a turning point in 20th century cosmology. It divided cosmology into an epoch of sometimes heated cosmological controversy (Kragh 1996) and an epoch of solidified support for the standard cosmological paradigm, popularly known as the hot Big Bang cosmology (Peebles, Page, and Partridge 2009). Actually, attributing the discovery of the CMB to Penzias and Wilson is a bit misleading, first, because they were not looking for it and, second, because it had been predicted by Gamow and his collaborators a few decades earlier.1 They initially interpreted the accidentally detected signal as a noise caused by an artefact; they were not aware it had anything to do with a physical phenomenon of the utmost importance for cosmology. Their detection of the signal had far-reaching implications, however, not least of which was a now overlooked interpretation race in which they themselves did not participate.
   The fact that the 1965 discovery was a clear watershed creates the impression of inevitability of the currently standard interpretation of the great CMB discovery as a remnant of primordial fireball, and that no alternative interpretations have been offered, seriously or half-seriously, by distinguished cosmologists. The impression of the inevitability of the current view is shared by astronomers and laypersons alike. Two of the best cosmology textbooks available, by Coles and Lucchin (1995) and Peacock (1999), reinforce this impression. Peacock even notes, with a poetic flourish, “The fact that the properties of the last-scattering surface are almost independent of all the unknowns in cosmology is immensely satisfying, and gives us at least one relatively solid piece of ground to act as a base in exploring the trackless swamp of cosmology” (p. 290).
   From the point of view of the astrophysics community, the validity of the orthodox interpretation of CMB is largely resolved, with some doubts voiced from time to time (e.g., Baryshev, Raikov and Tron 1996). And as far as the general issue of the choice of cosmological models is concerned, the standard cosmological model seems to rest on a secure foundation (for review of some exotic alternatives, see Ellis 1984).
   Yet López-Corredoira (2014) has quite recently examined some alternative cosmological models from a sociological point of view. This is important, as the emergence

1 There are claims of earlier CMB detections, as described Peebles et al. (2009). Normative understanding of scientific discovery correctly rejects such claims in the same manner as we reject the idea that Galileo discovered Neptune, although he did observe it in 1612-13, giving the credit to Le Verrier in 1846.
ALTERNATIVE EXPLANATIONS OF THE COSMIC MICROWAVE BACKGROUND

2 of alternatives and their destiny is a complex issue at the heart of scientific knowledge production and the discovery process. For instance, Cushing (1994) argues that a perfectly viable alternative to the Copenhagen interpretation of Quantu

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