A GREAT COINCIDENCE
A solar eclipse occurs whenever a New Moon passes directly between the Sun and the Earth. We do not see an eclipse at every New Moon because the Moon's orbit inclines about 5 degrees to the ecliptic. In most months, the Moon passes above or below the
Sun instead of across it.
Solar eclipses can be partial, or annular, depend on how much Sun is cover by the Moon. Total occur when the Moon the entire disk of the Sun. A total eclipse may last just second or two; the longest possible total eclipse is about 7 1/2 minutes.
It is pure accident that thg apparent sizes of the Moon and the Sun are roughly the same. The Moon is about 400 smaller than the Sun—but it also happens to be about 400 times closer. In fact, the Moon formed, its orbit been moving very slowly ward. From our point of view, it is steadily shrinking. Eventually, it will orbit too far from the Earth to ever completely the Sun, and total solar will be a thing of the past.
Because Earth is rotating and the Moon is moving, the I lunar shadow, or umbra, traces a curving path on Earth. The umbra barely reaches Earth, so the path is relatively narrow— where the Moon is directly overhead, the path will be at most about 170 miles (270 km) wide. This means that total eclipses are selective, occurring only rarely at any particular !place, although in most years there are one or two eclipses somewhere on Earth.
In recent decades, a new branch of the travel industry has developed, offering solar-eclipse expeditions to remote destinations. Tour-company advertisements start to appear in astronomy magazines about a year before the event.