Question

1. why dont we have a lunar eclipse every month?

Explanation:

A lunar eclipse occurs when the Earth is between the Sun and the Moon, and the Moon enters Earth's shadow. The Moon's orbit (lunar orbit) is tilted about 5° relative to Earth's orbital plane (ecliptic). So, the Sun, Earth, and Moon align (syzygy) for a lunar eclipse only when the Moon is near the ecliptic (during lunar nodes), not every month as the Moon's tilted orbit usually keeps it out of Earth's shadow.

Answer:

A lunar eclipse requires the Sun, Earth, and Moon to be aligned (Earth between Sun and Moon), but the Moon’s orbit is tilted ~5° relative to Earth’s orbital plane (ecliptic). Thus, the Moon usually passes above or below Earth’s shadow each month; alignment (and a lunar eclipse) only occurs when the Moon is near the ecliptic (at lunar nodes).