Why can a solar eclipse happen only at a new moon?

A solar eclipse can only occur during a new moon because this is the specific phase in the lunar cycle when the Moon is positioned directly between Earth and the Sun. During this alignment, the Moon has the potential to block the Sun's light from reaching Earth.12

It is important to note that a solar eclipse does not occur at every new moon. This is because the Moon’s orbital plane is inclined by approximately 5° relative to the ecliptic—the plane of Earth's orbit around the Sun. Consequently, the Moon often passes above or below the Sun from our perspective on Earth. For a solar eclipse to take place, the new moon must occur near a node, which is the point where the Moon’s orbit crosses the ecliptic.31