Blackett‘s Hypothesis of the Magnetic Field of Rotating Bodies

Abstract

PROF. P. M. S. BLACKETT¹ has recently directed attention to the well-known, but forgotten, fact that the ratio of magnetic moment &Pvec; and angular momentum &Uvec; is roughly the same for the sun and for the earth and can be written in the form, Here G is the gravitational constant, c the velocity of light and β a dimensionless constant of the order of unity, which Blackett estimates to be 0·130 for the earth and 1·14 for the sun. Furthermore, from Babcock‘s measurements Blackett deduces the value β = 1·16 for the star 78 Virginis, but since the mass, radius and angular velocity are all deduced statistically in this last case and the sign is unknown, only little weight can be attached to it.