The Moon, its phases and lunar eclipses

Light travels in straight lines. An opaque object, such as a ball, blocks the light, so a dark shadow forms behind it. A transparent object lets light pass, so it makes almost no shadow. When the light source is not a tiny point, the shadow has a very dark centre, and around it a lighter edge that gets some light from part of the source. The lighter edge is called the penumbra. In a dark room, a lamp, a ball and a white card show this. Think of the lamp as the Sun, the ball as the Earth and the card as the Moon. Safety: use a small torch or desk lamp with an adult; never look into a bright light, and never use the Sun.