On the Search for Hertzian Radiation Emanating from the Sun

Abstract

The remarkable discoveries by Hertz in 1889 concerning the propagation and nature of electromagnetic induction have presented the following question to astronomers: Is the new radiation, which is of the same nature as the caloric and luminous radiations, emitted by the Sun and received by the Earth? The answer to this interesting question has been provided almost directly by research, pursued on many fronts since 1895, on wireless telegraphy with the Hertzian waves over longer and longer ranges of transmission. The receiving instrument, whose sensitivity has been steadily increasing, comprises a Branly radio-conductor and a long wire called an antenna (more often than not vertical or inclined 40° to the vertical), which collects the waves. Consider the fact that during the day such an antenna continuously receives solar radiation, and yet the receiving instrument does not exhibit a continuous signal. Therefore, by reason of the large number of observations done under a great variety of conditions, and although the angle between the solar rays and the antenna is both variable and not always the most favorable, one is led to the following conclusion: the Earth does not continuously receive detectable Hertzian waves of length similar to those used in wireless telegraphy (between 10 m and 1000 m)¹. Moreover Messieurs Scheiner and Wilsing have especially investigated the solar Hertzian radiation, at first in 1896 and then in 1899,⋆ ¹ with a horizontal antenna, and recently M. Nordmann has resumed the same study on the slopes of Mont Blanc under conditions favorable in certain regards.

Comptes Rendus Acad. Sci. (Paris) 134, 527–530; translated from the French by W. T. Sullivan, III (1874).