Owen Gingerich (1998) The Tycho Illusion: Performing the Cutout Correctly. Psycoloquy: 9(52) Cognitive Illusion (11)

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PSYCOLOQUY (ISSN 1055-0143) is sponsored by the American Psychological Association (APA).
Psycoloquy 9(52): The Tycho Illusion: Performing the Cutout Correctly

Commentary on Margolis on Cognitive-Illusion

Owen Gingerich
Smithsonian Observatory
Harvard University
Cambridge MA 02138



Topper (1998) claims that the demonstration in Margolis (1998) will not work if a further cut is made to allow Mars to move. This is incorrect.


blindsight, cognitive illusion, mental image, persuasion, psychology of science.
1. In paragraph 5, Topper (1998) has written regarding Margolis's (1998) conclusions about the Tychonic system: "But of course there is no collision using the template this way, because the planets are not, in turn, moving around the sun (as they must do in the Tychonic system). The cut-out alone is incomplete; it only accounts for the motion of the sun around the earth, with the planets fixed in their orbits. Try to cut out the orbit of Mars in the template and rotate it around the sun. This cannot be done, because the spheres of Mars and the sun (if there were such spheres) overlap and hence collide."

    Figure 5 (Margolis 1998)


2. Topper has apparently failed to make the cuts correctly; hence his conclusion is incorrect. In another connection I wrote: "What convinced me was the following exercise. We [HM and OG] had a photocopy of the Tychonic system in front of us, and I had recently obtained a circle-cutting compass, so I cut a circle to include the earth-moon system, and a larger one just inside the fixed stars. This entire assembly could now rotate about the central, fixed earth axis. Next, setting the compass on the sun, it's possible to cut out a ring containing Mars, so this slip ring can turn around the sun to give a motion to Mars while the entire assembly goes around the earth."


Margolis, H. (1998) Tycho's Illusion: How It Lasted 400 Years, and What That Implies About Human Cognition PSYCOLOQUY 9 (32) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.32.cognitive-illusion.1.margolis

Topper, D. (1998) Margolis's Delusion: a Critique of "Tycho's Illusion." PSYCOLOQUY 9(42) Cognitive Illusion (7) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1998.volume.9/psyc.98.9.42.cognitive-illusion.7.topper

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