Earth’s shadow normally appears as a dark band low in the east after sunset. As Earth rotates, that band rises until it reaches an altitude of about 6°, then blends into the darkening sky (top). But when volcanic aerosols fog up the stratosphere, it’s possible for us to see Earth’s shadow impose itself on the glowing aerosol layer in the west after sunset (bottom). As Earth rotates, the dark shadow seems to “push” the aerosol glow down toward the western horizon until the shadow “snuffs” it out.
Astronomy: Roen Kelly