地球的磁力從那裏來??????

The origin of the earth's magentic field is still unkown to scientists. In fact, Einstein is said to have considered its origin one of the most important unresolved problem in physics.

In the early 20th Century, the "dynamo theory" was developed to explain the magnetic field origin. The dynamo mechanism is essentially a magnetic amplifier. Since 1939, the geomagnetic field has been believed to originate by convective motions in the fluid, electrically-conducting core of the earth. The idea is that the convective fluid interacts with the Coriolis forces produced by earth rotation and acts like a dynamo which is a magnetic amplifier. The idea seemed to make ense in explaining the origin of the observed geomagnetic field. However, there still remains a mystery on how the long-term, sustained convection could occur in the earth's fluid core.

It is not until the 1990s that the concept of a "georeactor", which is a nuclear fission reactor, was put forward. It is believed that such as reactor exists at the centre of the earth provides energy for generating the geomagentic field. The reactor works on uranium at the earth core, with a layer of fission products surrounding it.

Heat generated by nuclear fission is transmitted to the earth fluid and set up convection. Since the "georeactor" is surrounded by large amounts of neutron-rich radioactive fission-produced elements, with which beta decay yields electrons. The motion of these electron in the fluid core, coupled with Coriolis force, is responsible for the generating the earth's magnetic field.

You may wish to look at the follwing web-page for more details:

http://knol.google.com/k/origin-of-the-earth-s-magnetic-field#

來自南極及北極的磁場