What is the dark side of the Moon?
This phrase has sometimes been used – a bit archaically – to describe the side of the Moon that’s turned away from Earth. It’s not necessarily actually dark there – the sun does shine on it sometimes, as it does on the rest of the Moon – but the word dark in this context really means hidden from us. It’s probably better to call it ‘the far side’. It happens because the Moon and Earth have been so closely involved, gravitationally speaking, for so long, that the spin of the Moon has settled down to match its orbital speed around the Earth – in other words, the Moon always keeps more-or-less the same side facing the Earth. It naturally does this simply because the Moon is not exactly symmetrical, and its heavy side is naturally pulled more toward the Earth. It still has a bit of oscillation (wobble) remaining, but by and large we only ever see the same side of the Moon, from Earth. The far side had never been seen at all by humans until it was photographed, by one of the first automatic
