Achievement Award: Sample Solutions

Answer Just before the moon passes into the shadow of the earth it is almost collinear with the sun and earth and on the opposite side of the earth from the sun [1]. This means that when viewed from the earth it is fully illuminated (full moon) [1]. The orbit of the moon around the earth is not coplanar with the orbit of the Ear th around the sun [1]. A full lunar eclipse can only occur if full moon coincide s with the intersection of the planes of these two orbits [1]. Nearly all of this can be shown in a sketch. A complete absence of a sketch, which has been requested, even if all explained in text, removes one mark (i.e. maximum 3 without a figure).