if the earth is in between the sun and the moon, then the earth can block the light on the moon & the full moon is when the earth is in between the sun and the moon ->  the full moon is when the earth can block the light on the moon  the full moon is when the earth can block the light on the moon & an object blocking light causes a shadow ->  the full moon is when the earth can cause a shadown on the moon  the full moon is when the earth can cause a shadown on the moon & a lunar eclipse is formed by earth 's shadow falling on the moon -> the full moon is when a lunar eclipase can happen