Possible Method for determining the Planck Constant of Cosmic Photons

Abstract

SOME years ago, Bahcall and Salpeter¹ suggested that photons arriving from distant quasi-stellar objects (QSO) might not have the same Planck's constant, h, which we normally measure in the laboratory. In particular, they suggested a test which could be used to determine a dependence of h on the redshift parameter, z, of photons arriving from these objects. They proposed to measure the wavelength λ of such photons using a grating spectrometer. The photon energy ε could be independently measured by a prism instrument. The product could then be directly determined and compared with the product hc, obtained using a laboratory source. Existing measurements already imply a constancy of hc to about 1 part in 10³, where c and ν represent the photon speed and frequency.