Re: [Phys-l] An Unsolved Color Problem

["Dan Crowe" <Dan.Crowe@Loudoun.K12.VA.US>]

Humans perceive objects primarily by their edges, which are regions of
high contrast.  Color is determined to a large degree by contrast at
edges.  Square A appears dark because it is darker than the squares that
surround it; square B appears light because it is lighter than the
squares that surround it.  Sunspots appear to be black because they are
surrounded by regions that are much brighter; however, if you could take
a sunspot and move it away from the Sun, it would appear to be very
bright.  It's just that the photosphere around a sunspot is even
brighter.

Daniel Crowe
Loudoun Academy of Science
dan.crowe@loudoun.k12.va.us
> > > donald.polvani@ngc.com 07/17/07 8:08 AM >>>
 Here is the Astronomy Picture of the Day (APOD) for today July 17,2007.

http://antwrp.gsfc.nasa.gov/apod/astropix.html

I haven't "solved" the problem of how the two squares can appear to have
different colors and yet be the same color, so I have no need of coding
techniques to hide my solution.

I would, however, appreciate an (uncoded) explanation as to how the
squares can appear so different in color to the eye and yet be the same
color from anyone who knows the answer or can figure it out.

Don Polvani
Northrop Grumman Corp.
Undersea Systems
Annapolis, MD