The solar eclipse begins with the rising of the sun in the western regions of the earth’s surface and ends in the eastern regions when the sun sets. Usually a total solar eclipse lasts for several minutes (the longest total solar eclipse will be 7 July 29 seconds on July 16, 2186).
On the moon, too, there are solar eclipses. On Earth at this time, there are lunar eclipses. The moon moves from west to east, so a solar eclipse begins from the western edge of the solar disk. The degree of sun cover by the moon is called the phase of the solar eclipse. Complete solar eclipses can be seen only in those areas of the Earth, along which passes the strip of the shadow of the moon.
The diameter of the shadow does not exceed 270 km, so the total eclipse of the Sun can be seen only on a small part of the earth’s surface. Although solar eclipses occur more often than lunar eclipses, solar eclipses are observed much less frequently in lunar places in each individual place of the Earth. The plane of the lunar orbit in the intersection with the sky forms a large circle – the lunar path. The plane of the earth’s orbit intersects with the celestial sphere according to the ecliptic. The plane of the lunar orbit is inclined to the ecliptic plane at an angle of 5 ° 09 °. The period of revolution of the Moon around the Earth (stellar or sidereal period) P = 27.32166 earth days or 27 days 7 hours 43 minutes.
The plane of the ecliptic and the lunar path intersect with each other along a straight line called the knot line. The points of intersection of the line of nodes with the ecliptic are called the ascending and descending nodes of the lunar orbit. The lunar nodes are constantly moving towards the movement of the Moon itself, that is, to the west, making a full turn in 18.6 years. Annually, the longitude of the ascending node decreases by approximately 20 °. Since the plane of the lunar orbit is inclined to the ecliptic plane at an angle of 5 ° 09 °, the moon during the new moon or full moon may be far from the ecliptic plane, and the disk of the Moon will pass above or below the disk of the Sun. In this case, no eclipse occurs.
In order for a solar or lunar eclipse to occur, it is necessary that the Moon during the new moon or full moon be near the ascending or descending node of its orbit, i.e. near the ecliptic. In astronomy, many signs, introduced in ancient times, have been preserved. The symbol of the ascending node denotes the head of the dragon Rahu, who attacks the Sun and causes, according to Indian legends, its eclipse.
