References

Christianson G E 1995 Edwin Hubble Mariner of the Nebulae, The University of Chicago Press, Chicago

Hubble E P 1936 The Realm of the Nebulae, Yale University Press, New Haven

Sandage A R 1989 The Journal of the Royal Astronomical Society of Canada 83, 351

Acknowledgments -- I wish to thank Dr. P.S.S. Guimarães for reading the manuscript and for useful suggestions.

Left to right: Walter Sidney Adams (1876-1956), James Hopwood Jeans (1877-1946), and Edwin Powell Hubble (1989-1953) standing outside Mount Wilson Observatory. The photo was taken in the Spring of 1931. (Credit: AIP Emilio Segrè Visual Archives, Segrè Collection.