                        Astronomy Picture of the Day

    Discover the cosmos! Each day a different image or photograph of our
      fascinating universe is featured, along with a brief explanation
                    written by a professional astronomer.

                              2023 December 18
     A checkerboard is shown with squares colored light and dark grey. A
   green tube sits on the board and casts a shadow. The image has a letter
    A typed on a dark square, and a letter B types on a light square cast
      in shadow. The question is asked if the two squares, A and B, are
     really the same color. Please see the explanation for more detailed
                                information.

                           The Same Color Illusion
                 Image Credit: Edward H. Adelson, Wikipedia

   Explanation: Are squares A and B the same color? They are! To verify
   this, either run your cursor over the image or click here to see them
   connected. The featured illusion, an example of the same color
   illusion, illustrates that purely human perceptions in science may be
   ambiguous or inaccurate, even such a seemingly direct perception as
   relative color. Similar illusions exist on the sky, such as the size of
   the Moon near the horizon, or the apparent shapes of astronomical
   objects. The advent of automated, reproducible measuring devices such
   as CCDs have made science in general and astronomy in particular less
   prone to, but not free of, human-biased illusions.

         APOD Year in Review (2023): RJN's Night Sky Network Lecture
                   Tomorrow's picture: california on high
     __________________________________________________________________

       Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
            NASA Official: Phillip Newman Specific rights apply.
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                      A service of: ASD at NASA / GSFC,
                           NASA Science Activation
                             & Michigan Tech. U.

