Johann Karl Friedrich Zöllner
From 1872 he held the chair of astrophysics at Leipzig University. He wrote numerous papers on photometry and spectrum analysis in Poggendorff's Annalen and Berichte der k. sächsischen Gesellschaft der Wissenschaften, two works on celestial photometry (Grundzüge einer allgemeinen Photometrie des Himmels, Berlin, 1861, 4to, and Photometrische Unterstuchungen, Leipzig, 1865, 8vo), and a curious book, Ueber die Natur der Cometen (Leipzig, 1872, 3rd ed. 1883).
He discovered the Zöllner illusion where lines that are parallel appear diagonal. He also successfully proved Christian Doppler's theory on the effect of motion of the color of stars, and the resulting shift of absorption lines, via the invention of a very sensitive spectroscope which he named "Reversionspectroscope". He had shown also that the red-shift was in addition caused by variation in the stars' lights intensities with the help of his "Astrophotometer". He made the first measurement of the Sun's apparent magnitude. His result was very good, less than 0.1 from the modern value.
The lunar crater Zöllner is named in his honor.
Zöllner first became interested in Spiritism in 1875 when he visited the scientist William Crookes in England. Zöllner wanted a physical scientific explanation for Spiritism and came to the conclusion that physics of a four-dimensional space may explain spiritualism. Zöllner attempted to prove that spirits are four-dimensional and set up his own experiments with the medium Henry Slade. These experiments were recorded by Zöllner in a book titled Transcendental Physics in 1878. According to Zöllner the experiments were a success. Very few scientists however were convinced by Zöllner's experiments. Critics have pointed out that the medium Henry Slade was a fraud who resorted to trickery and that he had cheated on the experiments.
Martin Beech in The Physics of Invisibility: A Story of Light and Deception wrote:
|“||Zöllner presented his book as a physical investigation into the paranormal, including clairvoyance, matter transfer, ghosts and natural spirits. The main thrust of Zöllner's argument was that all these kinds of mystic phenomena could be explained if ghosts (spirits of the dead) inhabited a "real external world" composed of four spatial dimensions. On this basis, he argued that what we see as ghosts are really just shadows projected into our three-dimensional spatial realm.||”|
- One or more of the preceding sentences incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Zöllner, Johann Karl Friedrich". Encyclopædia Britannica 28 (11th ed.). Cambridge University Press. p. 1002.
- Anton Pannekoek A history of astronomy 1989, p. 385
- Rucker, Rudolf (September 1985). The Fourth Dimension: A Guided Tour of the Higher Universes. Illustrated by David Povilaitis. Mariner Books. pp. 53–55. ISBN 978-0395393888.
- William Hodson Brock William Crookes (1832-1919) and the commercialization of science 2008, p. 174
- Martin Beech The Physics of Invisibility: A Story of Light and Deception 2011, pp. 14-15