Why are solar eclipses so rare?

Solar eclipses are rare because even though the moon orbits the Earth once a month, it requires a very exact alignment between the Earth, sun and moon to create a solar eclipse. Even when the alignment occurs, the eclipse is limited to a small portion of Earth's surface.

Due to the orbital inclination of the moon, the conditions are right for a solar eclipse only a few times each year. In many cases, the eclipse is only partial, creating a penumbral shadow that partially obscures the sun's surface. A perfect alignment will create an umbral shadow that completely blocks the sun's disc, but the conditions may only be suitable for complete eclipse for a brief period as the moon travels across the sky.