GPS May 2020

illusions depicted on the two new stamps from the special postage
stamp series of the same name fool the viewer in different but different
ways. The optical illusion Two Shades of Gray? is called the Cornsweet
Illusion after the American experimental psychologist Tom Norman
Cornsweet (1929-2017) and is an example of the relativity of color and
brightness perception. There is an optical illusion if the subjectively seen
does not match the objectively measurable reality. Is that the motif of the
stamp two shades of gray? the case: the viewer does not see what is actually
there.
The Free Square on the stamp? The illusion shown here is called a
triangle puzzle and goes back to the American amateur magician Paul
Curry (1917-1986), who probably invented the riddle in 1953.
Deutscher Reichsbahn-Kalender
(23-25 März 1939)
Reichsautobahn, Reichsbahn and Landscape
This+ is a country with heavy all-round traffic, the Bergliche
Land, which is traversed by the Reichsautobahn Cologne - Düsseldorf
- Duisburg (-Berlin) and numerous, heavily used main lines of the
Reichsbahn. The picture shows the lines of the Reichsautobahn in
the area near Düsseldorf. It is crossed by the oldest railway in western
Germany, Düsseldorf - Wuppertal, on which heavy freight trains climb
the steepest incline.
(Thanks to Rainer Jaeschke for lending the GPS his copy of the
1939 Deutscher Reichsbahn-Kalender)
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