A Solar Eclipse happens when the Moon comes in between the Sun and Earth, blocking out the Sun's rays fully or partially and casting a shadow on portions of Earth. This occurs when the Sun, Moon and Earth are in the same line. It occurs only on new moon day because new moon occur
s when the Moon is between the Earth and the Sun, so the side facing us is the dark side. If lined up correctly, the Moon casts a shadow on us such that we get a solar eclipse.