Nebulae. Offprint from: Proceedings of the American Philosophical Society, vol. LVI, no. 5, 1917

SLIPHER, Vesto Melvin

Published by American Philosophical Society], [Philadelphia, PA, 1917

THE FIRST OBSERVATIONAL EVIDENCE FOR THE EXPANDING UNIVERSE. First edition, extremely rare separately-paginated offprint, of the paper which "provided the first evidence supporting the expanding-universe theory" (Britannica). In this profoundly significant paper, Slipher reports his finding that, of 25 spiral 'nebulae' examined, 21 are receding from us at high velocities, thus anticipating Hubble in his two most important discoveries: that the universe is expanding, and that the nebulae are separate galaxies outside our own, implying that the universe is vastly larger than our own Milky Way galaxy. "For the eminent cosmologist Fred Hoyle (1915-2001), Slipher's pioneering observations of redshifts [i.e. velocities of recession] should have led to his being credited with the discovery of the expanding universe" (Kragh & Smith, p. 143). When in 1929 Hubble published the law now named after him stating that galaxies were receding from us at velocities proportional to their distance away, it was Slipher's velocity measurements he was using, although he neglected to give Slipher any credit at the time. Slipher deduces in this paper that the nebulae are receding at a mean relative velocity of 700 km/s and makes a tremendous intellectual leap: "For us to have such motion and the stars not show it means that our whole stellar system moves and carries us with it. It has for a long time been suggested that the spiral nebulae are stellar systems seen at great distances . This theory, it seems to me, gains favor in the present observations" (p. 7). This was eight years before Hubble measured the distance of the Andromeda nebula and settled definitively the 'island universe' question of whether the nebulae were objects inside or outside the Milky Way. "Vesto Melvin Slipher, a pioneer in the field of astronomical spectroscopy during his long career at Lowell Observatory at Flagstaff, Arizona, probably made more fundamental discoveries than any other observational astronomer of the twentieth century" (Hoyt, p. 411). OCLC lists Observatoire de Paris only. RBH lists only Edwin Hubble's copy (Christie's, 16 July 2020, lot 8, £10,625). In 1901, Slipher (1875-1969) took a position working at the new Lowell Observatory with Percival Lowell (1855-1916). Gradually, Slipher became highly skilled with the observatory's spectrograph, learning to take spectra of planetary atmospheres. In 1909 Lowell asked Slipher to turn his attention to the long-standing problem of the spiral nebulae, which Lowell believed were solar systems in the process of formation within the Milky Way. "For three centuries astronomers had observed and speculated about these numerous, but faint, diffuse objects, yet almost nothing about them was then known. Some believed that they were vast aggregations of stars beyond the Milky Way, 'island universes' as suggested by philosopher Immanuel Kant in 1755. Others felt they might be embryonic planetary systems in early stages of evolution and thus analogs of the primordial solar system . [Lowell] thought that if such objects were indeed incipient solar systems, they might show spectrographic similarities to the solar system itself. Early in 1909 he asked Slipher to observe what were then only classified as 'green' and 'white' nebulae, the latter group containing the enigmatic spirals, and to compare the spectra of their 'outer parts' with his spectra of the giant outer planets" (Hoyt, p. 421). It took Slipher four years of difficult and demanding work before he obtained significant results: he detected a blue-shift in the wavelength of light from the Andromeda nebula due to the Doppler effect, indicating that the nebula was moving at high speed toward us. "On February 3, 1913 he wrote Lowell that the Great Nebula in Andromeda was approaching the earth at the then unheard-of speed of 300 km/sec, the value, incidentally, that is accepted today. "It looks as if you had made a great discovery," Lowell replied. "Try some other spiral nebulae. Seller Inventory # 6189

Bibliographic Details

Title: Nebulae. Offprint from: Proceedings of the ...
Publisher: American Philosophical Society], [Philadelphia, PA
Publication Date: 1917
Edition: First edition.