by John G. Cramer Alternate View Column AV-150

1 Problem In two recent e-prints, Tuval and Yahalom proposed " electromagnetic spaceships " based on the net force exerted on a pair of time-dependent current loops [1], or a time dependent current loop and a permanent magnet [2]. Show that rocket propulsion (net gain of mechanical momentum of an isolated system) is possible in the first example, but not in the second. Ampère argued [3] that th...