Is the dark side of the Moon really dark?

Thanks to a famous rock album and decades of sci-fi, the dark side of the Moon sounds like a place of eternal night, full of secrets and maybe a villain’s lair. The reality is far sunnier. Literally. The hidden half of the Moon gets its fair share of daylight, and over time it actually gets slightly more than the side we see.

The short answer

There is no permanently dark side of the Moon. The half we never see from Earth gets just as much sunlight as the half we do. NASA’s education pages put it simply: the only dark side of the Moon is whichever side happens to be pointing away from the Sun at that moment. Astronomers prefer the term far side.

The real story

The Moon shows us the same face all the time because of tidal locking. It takes about the same time to spin once on its axis as it does to orbit Earth, roughly four weeks. So as it travels around us, it turns at just the right rate to keep one side facing our way. That has nothing to do with sunlight. As the Moon orbits, the Sun sweeps across its whole surface, so every part gets a day and a night, each lasting about two of our weeks.

In fact, when we see a new moon, with the near side looking dark to us, the far side is bathed in full sunshine. According to BBC Sky at Night Magazine, if you count the times the near side spends in Earth’s shadow during lunar eclipses, the far side actually comes out slightly ahead on sunlight.

We do get a small peek around the edges. Slight wobbles in how the Moon appears from Earth, called libration, let us see a little more than half its surface over time. Even so, most of the far side stayed a mystery until the space age. The Soviet probe Luna 3 took the first photographs of it on 7 October 1959. They revealed a surprisingly different landscape: heavily cratered, with far fewer of the smooth, dark plains called maria that give the near side its familiar face.

Nothing made a soft landing there until 2019, when China’s Chang’e 4 touched down. (NASA’s Ranger 4 had crash-landed on the far side back in 1962.) One reason it took so long is that the Moon itself blocks radio signals from Earth, so a far-side lander needs a relay satellite to phone home. China’s Chang’e 6 followed in 2024.

Why people get it wrong

The word dark has more than one meaning. For centuries, the far side was dark in the sense of unknown, because nobody had seen it. It is also dark in the radio sense, since spacecraft there are cut off from direct contact with Earth. Those meanings slid into the literal idea of a place without light. Then a hugely popular album by Pink Floyd cemented the phrase in everyone’s heads.

It is an easy mix-up: never seen sounds a lot like never lit. But the Moon is not hiding anything in the shadows. It just keeps its back to us.

“I used to think it was pitch black round there too. Turns out the Moon’s just got one good side for photos, mate. Can’t blame it, really.”