What is one reason why a lunar eclipse might not occur at every full moon?

A lunar eclipse occurs when the Earth positions itself directly between the Sun and the Moon, resulting in the Earth's shadow falling on the Moon. For this alignment to take place, the Moon must be at the full moon phase. However, the Moon's orbit is tilted relative to the Earth's orbital plane around the Sun by about 5 degrees. This tilt means that during most full moons, the Moon is either slightly above or below the direct alignment needed for a lunar eclipse to occur.

If the Moon's orbit were perfectly aligned with the Earth's orbit, we would see a lunar eclipse every full moon. However, due to this tilt, the chances of the Moon falling into the Earth's shadow are reduced, resulting in lunar eclipses happening only under certain conditions during specific full moons throughout the year. This phenomenon illustrates the importance of orbital mechanics and the three-body gravitational interactions between the Earth, Moon, and Sun in determining when eclipses occur.