English and Spanish Translation of Zwicky's (1933) The Redshift of
  Extragalactic Nebulae
  English and Spanish translations are provided for Fritz Zwicky's seminal
article on "The Redshift of Extragalactic Nebulae", published in German in
Helvetica Physica Acta in 1933
<https://www.e-periodica.ch/digbib/view?pid=hpa-001:1933:6#112>. This paper is
usually cited as the first evidence for dark matter ("dunkle Materie", not
"missing matter"). Zwicky's conclusion is based on the velocity dispersion of
only seven galaxies in the Coma cluster of galaxies. Now, 84 years later, with
1000+ radial velocities measured for Coma cluster members, Coma's velocity
dispersion is very close to that found by Zwicky. The translation is as literal
as possible, and annotations on the translation of certain terms are given.
Doubts on the meaning of the original phrasing are given in square brackets at
a few places where they occur. The pdf version of my English translation was
kindly prepared by Cren Frayer at the NASA/IPAC Extragalactic Database (NED),
also available at NED's Level5 repository since June 2017
(<http://ned.ipac.caltech.edu/level5/March17/Zwicky/frames.html>). A Spanish
translation, without figures, prepared by myself with the help of Martha
Margarita L\'opez Guti\'errrez is appended within the same pdf file. As
translator I take responsibilty for the quality of the translation.
