The Earth is surrounded by a large magnetic_field, which reaches from the magnetosphere far into space. It protects the Earth from the solar_wind.
It is thought that the first magnetic field of the Earth was generated when the Earth, then still a swirling mass of gas and dust, penetrated the magnetic field of the Sun several million years ago. Consequently, electrically conductive matter within the mass of the Earth was magnetized, exciting electrons (charged particles). Their movement produced an electric current, generating an independent magnetic field.
In 1600, William Gilbert, scientist and physician to Queen Elizabeth I of England, promoted the theory that the Earth was comparable to a huge magnet. However, the effects of this magnetism had been known for a long time and were utilized for navigation with a compass.
Although there is no actual magnet in the interior of the Earth, the magnetic field can be compared to one. It has two opposing poles and is thus known as a dipole_magnetic_field.
As this field is at an angle of about eleven degrees to the axis of rotation of the Earth, the magnetic north and south poles do not correspond exactly to the geographical poles. For this reason, the compass needle can only give an approximation of the geographical north.
The magnetosphere is strongly affected by solar_winds. On the side facing the Sun it reaches out to between eight and ten times the Earth's radius, while on the other side it extends tail-like far beyond the path of the Moon (over 1000 times the Earth radius). It is shaped like a streamlined teardrop.
