A magnetic field is a vector field responsible for generating forces on electrically charged objects and magnets. Magnetic fields are generated by magnetic dipoles, moving electric charges, or changing electric fields.
Magnetic fields are linked to electric fields; light, for instance, is a propagating electric and magnetic wave. Relativistically, a magnetic force in one inertial frame corresponds to an electric force in another.
When trying to determine the magnetic forces and fields, the right hand rule often proves useful.
Earth's Magnetic Field
The magnetic field of Earth is directional nearly north-to-south, although slightly askance, meaning that "magnetic north" is not the same as "true north," and a person who is orienteering must take into account this change of declination, although it is truly only marginally relevant, unless you are close to either pole. This field has been decaying at a rapid rate of about about 5% per century, which casts doubt on the theory that the Earth is billions of years old. This decay suggests that, at some point, the poles will invert.
Scientists have speculated about the history of Earth's magnetic field. One group that makes use of the Bible as a resource for science suggests that the history of the Earth's magnetic field is as depicted to the right.
- Boy Scout Handbook.
- K.L. McDonald and R.H. Gunst, 'An analysis of the earth’s magnetic field from 1835 to 1965,’ ESSA Technical Report, IER 46-IES 1, U.S. Govt. Printing Office, Washington, 1967.