On the Minimum Energy Necessary for Visual Sensation

(Henry Norris Russel. The minimum radiation visually perceptible. Astrophysic. Journal. Vol. 45, No. 1, p. 60, 1917).

The question of the minimum energy necessary for producing sensation is of interest not only from the practical point of view in the study of faintly shining stars, but also has great significance for substantiating the ionic theory of excitation, since the identical order of magnitude of the energy necessary for the minimal stimulation of vision and hearing shows that, in the excitation of the terminal nerve endings, we are dealing with processes analogous in their physico-chemical character. [Details on the numerical relations the reader may find in P. Lazarev’s book: Investigations on the Ionic Theory of Excitation, p. 154. Moscow, 1916.] The newest investigations of Ives (Astroph. Journal, 44, p. 124—1916) showed that the minimum amount of light energy necessary for threshold sensation must be much smaller than was found in earlier works; Russel’s work, carried out with great precision, revealed that Ives’s values must be regarded as large, and that the minimum energy perceptible by the eye corresponds to 200 energy quanta per second, or to one gram-calorie in the course of 1,700,000,000 years.

P. Lazarev.