What if we could see the far side of the Moon?

Look up at the Moon. You always see the same patterns. That is because the same side always faces us.

What does the other side look like? Let's find out!

Every night the Moon shows the same face, with the same dark patches that some people imagine as a face. That's because one side of the Moon always points toward Earth. The other side, the far side, never faces us.

So what if we could see the far side from Earth? What would it look like, and why can't we see it now? This is a thought experiment. Choose a path to find out why one face points at us, what spacecraft found on the far side, and how a rover drove across it.

The Moon's rotation is synchronized with its orbit, so the same hemisphere always faces Earth. NASA notes that the far side is sometimes called the dark side, but that is misleading: it goes through the same full cycle of phases as the near side, only never seen from Earth.

This thought experiment imagines seeing that hidden hemisphere from home. The evidence comes from spacecraft imaging, from Luna 3 in 1959 to NASA's Lunar Reconnaissance Orbiter, from Apollo crews who orbited the Moon, and from the Chang'e 4 landing. The scenario of a far side turned toward Earth is an idea, not something that can happen as the Moon moves today.

The Moon does spin, very slowly. It spins once each time it goes around Earth.

So it keeps the same side toward us, like a dancer always facing a partner.

It might seem the Moon doesn't spin, but it does. NASA explains that the Moon takes exactly as long to spin once as it does to go around Earth, about 27 days. So it never turns its back on us, like a dancer circling a partner while always facing them.

The near side has large dark patches called maria, seas of cooled lava. The Moon's phases happen because different parts are in sunlight at different times. At new moon, when we see no lit Moon at all, the far side is in full sunlight.

The Moon completes an orbit in about 27 days and rotates in the same time, a state called synchronous rotation, or tidal locking; because Earth is also moving, the cycle of phases we see takes about 29 days. NASA notes all of the solar system's large moons are tidally locked to their planets.

Illumination is independent of which side faces us. At full moon the near side is fully lit; at new moon the far side has full sunlight while the near side is in night. The near side's dark maria are lava that flooded impact basins between 4.2 and 1.2 billion years ago, standing out against the brighter, older highlands.

Imagine the Moon turned around. The big dark patches would be gone!

You would see bright ground covered in round craters instead.

Imagine the Moon turned its far side toward us. NASA's maps show it would look very different. The big dark patches we know would mostly be gone. Instead, craters of all sizes would crowd together across its whole face, and a huge, slightly darker basin would cover the bottom part.

The Moon would still go through phases, because the far side has days and nights just like the near side. We would just see a new pattern of light and shadow. That's an idea of the view, made from real spacecraft maps.

NASA's visualization of the far side, built from Lunar Reconnaissance Orbiter maps, shows a hemisphere lacking the large maria of the near side, densely cratered at every scale, with the South Pole-Aitken basin, one of the largest and oldest impact features in the solar system, appearing as a darker region across the lower third.

Seen from Earth, that face would still run through a full cycle of phases. Turning the Moon around is purely an idea: tidal locking holds the present orientation, and the lab does not model any process that could change it.

Earth's pull stretched the young Moon, like a squished ball.

That stretching slowed the Moon's spin until one side always faced Earth.

When the Moon was young and hot, NASA explains, it spun much faster. Earth's gravity pulled it into a stretched shape, with a bulge. As the Moon spun, the bulge kept being tugged back toward Earth, and that tug of war slowed the spin.

Eventually one spin took as long as one trip around Earth, and the bulge stopped shifting. That's tidal locking. Earth's pull still gives the Moon a slight football shape today.

NASA describes how tidal locking began at the Moon's birth. The young, molten Moon spun rapidly while Earth's gravity raised a bulge on it. Because material takes time to rise and fall, the bulge always lagged slightly out of alignment and was pulled back by gravity; the flexing dissipated energy as heat and slowed the rotation.

Once a spin matched an orbit, the bulge no longer shifted relative to Earth and the spin rate stopped changing. Tidal forces have also pushed the Moon outward; it still recedes about 4 cm a year. Why the two hemispheres differ is a separate puzzle: the far-side crust is about 60 km thick against about 40 km on the near side, and scientists are still working out why.

In 1959, a spacecraft took the first pictures of the far side. Later, astronauts flew around the Moon.

In 2019, a lander and a rover from China landed there!

People first saw the far side in a few grainy pictures from the Soviet spacecraft Luna 3 in October 1959. In December 1968, NASA's Apollo 8 crew became the first humans to orbit the Moon, and in 1969 the Apollo 11 crew photographed a far-side crater as they circled the Moon.

In January 2019, China's Chang'e 4 became the first mission to land on the far side, in a crater about 186 kilometers wide. Its rover, Yutu-2, had driven at least 502 meters by October 2020, according to the team at Arizona State University that images it with NASA's Lunar Reconnaissance Orbiter.

Luna 3 returned the first, grainy far-side images in October 1959; NASA's LRO, launched fifty years later, has since returned hundreds of terabytes of mapping data. Apollo 8, in December 1968, was the first crewed lunar orbit, and in 1969 the Apollo 11 crew photographed far-side features such as the 30 km Crater 308.

Chang'e 4 landed on 3 January 2019 in Von Kármán crater, 186 km across, inside the South Pole-Aitken basin. ASU's LROC team reports it was the first far-side landing, tracked Yutu-2 for at least 502 m by 18 October 2020, and notes the far side is a radio-quiet zone, shielded by the Moon from Earth's radio noise.