The solar eclipse occurs when Earth, the Moon and the Sun are on one line, at the same time the Moon in whole or in part closes a solar disk. Solar eclipses occur more often lunar when the Moon disappears in a shadow from Earth, but it is possible to observe them less often as the territory where this phenomenon, small is visible.
Solar eclipse
When the Moon rises on one line between the Sun and Earth, from the surface of the planet it is possible to observe a solar eclipse – the disk of the Moon gradually closes the Sun, leaving a pale solar crown. At the same time the satellite casts a dense shadow which falls on a certain site on Earth. If the observer is in this site, he sees a total solar eclipse when the disk of the Moon completely closes a disk of the Sun. Near this shadow it is possible to observe a partial eclipse which looks as if the Moon passes not exactly in the middle of the Sun, and sideways, leaving visible its part.
So far the total eclipse is possible as the satellite is at rather small distance from Earth and can close completely a disk of the Sun, but through several hundreds of millions of years, according to the estimates of scientists, it will become impossible as the Moon will move away from our planet. Only ring-shaped eclipses which sometimes happen and now when the Moon is further from Earth will be possible (a satellite orbit elliptic). As a result the cone of a shadow does not reach the Earth's surface, and it is possible to observe how the disk of the Moon comes on the middle of the Sun and forms a bright ring.
Solar eclipses occur only in a new moon when the Moon is not visible as that party which is turned to the Sun is lit. The eclipse lasts several minutes – the shadow of the Moon on the Earth's surface slides with a speed about one kilometer per second.
Frequency of solar eclipses
Average frequency of solar eclipses – 2-3 in a year, but in separate years can occur and 5 eclipses. Less than 2 such phenomena a year do not occur. Lunar eclipses happen less often, but they can be observed on a half of the globe whereas solar are visible only on the small site therefore they are considered as rare. Eclipses of the Sun, as well as lunar, have the frequency connected with sarosy – time for which the Moon makes 223 revolutions. Saros makes 18 years and 11 days, during this time there are 41-43 eclipses. This inexact number as duration of a saros changes over time. Eclipses pass in a certain order (full, partial, ring-shaped), and after one saros this order repeats again. Therefore it is approximately possible to foretell when there is an eclipse and what character it will have. If to consider the frequency of solar eclipses in centuries, for one century there are on average about 240 eclipses.