An excerpt of an article by Ernest O. Lawrence and J. W. Beams in the July 2012 issue of Scientific American:

"Light is one of the most familiar physical realities. All of us are acquainted with a large number of its properties, while some of us who are physicists know a great many more marvelous characteristics which it displays. The sum total of our knowledge of the physical effects produced by light is very considerable, and yet we have no satisfactory conception of what it is."

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