Albert Einstein, 1905
"One should, however, bear in mind that optical observations refer to time averages and not to instantaneous values ... (to provide) the complete experimental verification of the theory of diffraction, reflexion, refraction, dispersion, and so on ... In fact, it seems to me that the observations on 'black-body radiation', photoluminescence, the production of cathode rays by ultraviolet light and other phenomena involving the emission or conversion of light can be better understood on the assumption that the energy of light is distributed discontinuously in space (photons)."
Max von Laue, 1906
"...hence, radiation does not consist of light quanta (photons) as it says in § 6 of your (Einstein's) first paper (1905); rather, it is only when it is exchanging energy with matter that it behaves as if it consisted of them."
Max Planck, 1913
" ...for instance in his (Einstein's) hypothesis on light quanta (photons), he may have gone overboard in his speculations..."
Robert Millikan, 1916
"We are confronted, however, by the astonishing situation that these facts were correctly and exactly predicted nine(sic) years ago ... (by a) bold, not to say reckless, hypothesis of an electromagnetic light corpuscle (photon)...which flies in the face of thoroughly established facts of interference."
Niels Bohr, 1922
"The hypothesis of light quanta (photons) is not able to throw light on the nature of radiation."
Gilbert Lewis, 1926
"I therefore take the liberty of proposing for this hypothetical new atom, which is not light but plays an essential part in every process of radiation, the name photon."
Paul Dirac, 1930
"Each photon then interferes only with itself. Interference between two different photons never occurs."
Sir William Henry Bragg, c.1930(?)
"Light is waves on Mondays, Wednesdays, and Fridays; it's particles on Tuesdays, Thursdays, and Saturdays, and on Sundays, we think about it!" (There are many variants of this quote)
Albert Einstein, 1951
"All these fifty years of conscious brooding have brought me no nearer to the answer to the question, 'What are light quanta (photons)?' Nowadays every rascal thinks he knows, but he is mistaken."
Richard Feynman, 1979
"In fact, both objects (electrons and photons) behave somewhat like waves, and somewhat like particles. In order to save ourselves from inventing new words such as wavicles, we have chosen to call these objects particles."
Willis Lamb, 1995
"...there is no such thing as a photon. Only a comedy of errors and historical accidents led to its popularity among physicists and optical scientists."

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On 3 Mar 2006, 19:54.