Globular Clusters, Cepheid Variables, and Radiation

Abstract

DR. SHAPLEY makes the suggestion (NATURE, March 13) that known supplies of energy become adequate to maintain stellar and solar radiation through astronomical time if we can suppose that radiation is propagated only from matter to matter, and is not radiated equally in all directions. In brief, we see the sun because the sun has in some way first seen us. Prof. Soddy points out (NATURE, March 20) that we have no direct evidence of loss of radiation into space; “experiment and observation justify only the conclusion that radiation is propagated between portions of space occupied by matter, … elsewhere it may not be propagated at all.” Prof. Soddy is, perhaps, on safe ground as regards laboratory experiments, but it seems to me that astronomical evidence is against him.