A method has been developed to determine the geometrical parameters of surface distributions of chemical elements on a spotted rotator from observations of variable line strengths. On the basis of simple assumptions for spot geometry and limb darkening this problem has been traced back to the same inverse problem as the determination of surface brightness parameters from photometric observations. The method was applied to eight He-peculiar (CP4) stars (HR 1441, HR 1890, HR 1932, H D 37776, HR 2509 to derive the He surface distribution of these He-rich and He-weak stars from the line strength variation of the He1 R 4026 line. The result and a discussion of the analysis is given.

Gravitomagnetism is a low velocity and weak gravitational field approximation of general relativity. It provides a simple approach to post-Newtonian gravitational phenomena via electromagnetic analogy. Intended for advanced undergraduate students, the present paper applies gravitomagnetism to the quantitative study of the geodetic precession and frame dragging effects, both verified recently in the Gravity Probe B experiment. The result obtained is identical with Schiff's formula.

The Machian effect of distant masses of the universe in the frame of reference of the rotating Earth is demonstrated using the gravitomagnetic approach of general relativity. This effect appears in the form of a gravitomagnetic Lorentz force acting on moving bodies on the Earth. The gravitomagnetic field of the universe—deduced from a simple model—exerts a gravitomagnetic Lorentz force on moving bodies, a force parallel to and with comparable strength to the Coriolis force observed on the rotating Earth. It seems after simple considerations that the Coriolis force happens to be the gravitomagnetic Lorentz force exerted by the mass of a black hole universe. The description of the phenomenon is simpler using the gravitomagnetic approach than the standard formulation of general relativity, so the method relying on gravitomagnetism is advisable in lectures intended for master’s degree level physics students and advanced undergraduates.