This is composed of rocky material which gives way to the crustal rocks about 30 km from the surface of the Earth. The Earth also possesses a magnetic field which is believed to be generated in the outer core by the motion of the liquid metal. The Earth possesses one natural satellite, the Moon. A chance alignment between the Sun and two other celestial objects within the solar system in which one body blocks the light of the Sun from the other. In effect, the outer object moves through the shadow of the inner object.
Lunar eclipses occur when the Earth passes directly between the Moon and the Sun.
See also occulation . Solar eclipses occur when the Moon passes directly between the Sun and the Earth. Partial solar eclipses occur when the alignment is not perfect. Annular eclipses occur if the Moon passes directly between the Earth and the Sun but it is at the furthest point of its orbit, so it does not quite cover the Sun. In this case an annulus of sunlight remains and the corona becomes strikingly visible around the silhouette of the Moon.