SUBJECT: The Earth and a Giant Dip Needle (Far)
DESCRIPTION: This animation illustrates a hypothetical scenario in which an enormous dip needle (a compass whose needle can osciallate in a vertical plane) is placed on the surface of the earth and oscillates undamped in the earth's field. The oscillation is of course a result of the interaction between the magnetic field of the earth and the magnetic field generated by the dip needle. If the needle's oscillatons were damped, it would align itself along the local magnetic field. Note how the total field is stretched and compressed as the needle oscillates, in keeping with the Maxwell stresses that cause the oscillation of the dip needle.
VISUALIZATION (MPG - 2 MB)