In Origins of the Expanding Universe: 1912-1932. Proceedings of a conference held 13-15 September, 2012, at Flagstaff, Arizona, USA. ASP Conference Proceedings, Vol. 471. San Francisco: Astronomical Society of the Pacific, 2013., p.63.
http://arxiv.org/abs/1301.7509

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SLIPHER AND THE NATURE OF THE NEBULAE

Ken Freeman


The Australian National University


Abstract: Why do some discoveries, which appear in hindsight to be obviously major discoveries, have so little impact when they were made. These are discoveries that were ahead of their time, but for some reason the scientific community was not ready to absorb them. I got interested in Slipher after learning that by 1914 he had observed nebular redshifts up to 1000 km s−1. Why did this not convince people at the time that the nebulae were extragalactic ? Was this another example, like Zwicky's (1933) discovery of dark matter in the Coma cluster, of a discovery which was too far ahead of its time ? I conclude that Slipher's situation was different from Zwicky's. The significance of Slipher's nebular redshifts was partly recognised at the time, but I believe that its full significance was masked by van Maanen's work which turned out to be erroneous and reduced the impact of Slipher's discoveries.


Table of Contents

INTRODUCTION

ZWICKY'S DISCOVERY OF DARK MATTER IN THE COMA CLUSTER

KAHN & WOLTJER (1959)

TWO DISCOVERIES THAT HAD AN IMMEDIATE IMPACT

SLIPHER'S CONTRIBUTION TO NEBULAR SPECTROSCOPY

HUBBLE AND THE DISCOVERIES OF OTHERS

REFERENCES

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