The passage of the shadow of a celestial body over the surface of another. The maximum number of solar and lunar visible eclipses occurring annually is seven; the minimum number is two, both being solar. Solar eclipses take place when the new Moon is close to an orbital node and on the same longitude with the Sun. At that moment either the umbra, antumbra, or the penumbra touches the Earth's surface. For an observer located in the umbra the eclipse is total, while for one placed in the antumbra it is annular. Annular eclipses occur around lunar apogee. An observer situated in the penumbra sees only a partial eclipse. A total or annular eclipse can be seen from a band with a width of 270 km at the most, around which, the much larger partiality zone extends. The Moon's shadow crosses the Earth from west to east at about 3,200 km/h. During total eclipses the Sun's disk is entirely covered and the solar corona can be seen. A solar eclipse can last up to 3h (between the first and the fourth contacts). Totality has a theoretical maximum duration of 7m 31s, but it is usually shorter. A lunar eclipse can be seen from any place on Earth where the Moon is above the horizon; it occurs when the full Moon passes through the central dark shadow of the Earth. The Earth's shadow is much wider than the Moon and this is why the lunar eclipses can last up to four hours (between the first and the fourth contact).