The moon as only space tourists will see it

Imagine yourself a space tourist, standing on the moon and looking back at those fluff-white clouds gliding across the Earth. You can gaze on that view as long as you like, but you’ll never see Earthrise nor Earthset from the surface of the moon. The Earth will stay in one place and instead of watching it travel across the sky, you'll get to watch it spin.

Our 1st glimpse of the far side, 1959/Luna 3, by OKB-1

You would see the Earth spin from the moon because the moon takes the same time to make one full rotation as it takes to orbit the Earth, a little over 27 days. As a result, the moon always shows us the same face. It’s a leisurely rotating pace compared to the Earth’s whirling, 365 times for each single orbit around the Sun.

Long ago, when the moon was young, it span a lot faster. As it did so, the Earth’s gravity was felt more strongly on whichever part of the moon was facing the Earth, just as the moon’s gravity tugs at the Earth’s oceans to produce tides. The tug of gravity pulled on the moon's rocks, and created a bulge. Rock is not amenable to changing shape as oceans are, so it took some time for the bulge to form. By then, the moon had continued on its orbit, spinning as it went. A different part of the moon faced the Earth, but that bulge hadn't yet disappeared. Until it did, it dragged on the moon’s spinning, slowing the moon’s rotation a little. Over time, the moon spun slower and slower, until finally it slackened to match the moon's orbit. The moon had become tidally locked, and hence always showed the same face to the Earth.

The same side of the moon always "faces" the Earth

This phenomenon of tidal locking is not uncommon - the major moons of Jupiter and Saturn also take the same time to spin as they take to orbit around their planets.
Nor is it a fate reserved for moons. Pluto and its moon Charon are tidally locked to each other, and so never show each other their backs.

Eventually, the moon’s smaller gravity will be enough to lock Earth's spinning to the moon too, but by then the sun will be long dead, and may have even have engulfed the Earth, so we won’t be here to see it.

Far side of the moon/
by NASA,GSFC,Arizona State University

Of course, the far side of the moon isn’t always dark. When the far side faces into the sunlight, the side facing us is in darkness, a new moon. When the near side is fully in the sunlight, we see a full moon.

While the far side isn't always dark, it is always quiet. The radio waves we transmit from Earth travel out of our atmosphere and into space, but they can’t reach the far side of the moon. That would make it a great place for radio telescopes, particularly for radio astronomers hoping to learn about the “dark ages”, the time after the Big Bang before the formation of the first stars. Astronomers hope that low energy radio waves will reveal part of the universe’s early story, but interference from our own broadcasting, and the reflection of radio waves from the upper layers of our atmosphere, prevent these signals from being detected on Earth. The far side of the moon doesn't have these limitations, which means it might get far more attention in years to come. Watch this face.



Further reading:

What causes tides? NASA/NOAA SciJinks

Put telescopes on the far side of the moon, Nature, 3 January 2018

Luna 3, NASA/NSSDCA