Imagine a scenario where the moon is not tidally locked with one side facing the earth but where it is able to rotate about its own axis. This could be due to a larger distance from earth or a mildly smaller mass of our planet. My question is how would this changing face of the moon as viewed from the earth affect the development of humans. People have observed and worshipped the moon for millennia so a rotating moon must certainly have an effect on mankind.

This could have led to the discovery that celestial bodies are spherical earlier and led to the introduction of a heliocentric model earlier. Perhaps we could even have reached the space age centuries earlier.

What other possible effects might such a scenario have on a human population here on earth?

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    $\begingroup$ By bad luck, this question has been asked while another moon-related question ("Can a planet without one or more moons be habitable?") is also active. The questions are different, yours being about culture and history while the other one is about whether life is physically possible at all. I am going to edit your title to differentiate the two questions more. If you don't like my wording, feel free to change it. $\endgroup$ – Lostinfrance Mar 15 '16 at 8:03
  • $\begingroup$ No the wording is good thanks for pointing it out $\endgroup$ – Jaywalker Mar 15 '16 at 9:42
  • $\begingroup$ To be fair, rotating moon or no, I'm not sure materials science would change enough to move up the first workable rocket engines by centuries. Werner Von Braun probably wasn't the first person smart enough to get to orbit, but he may have been the first to have the funding, the math, the vision and the manufacturing capabilities all come together. To move it up by centuries would require a vastly different history, one in which scientific progress was more important than the kind of destructive conquest that created Rome. Then again, it's hard to get resources together without an empire... $\endgroup$ – Sean Boddy Mar 15 '16 at 12:02
  • $\begingroup$ In addition to this, the discovery that celestial bodies were spherical was made relatively early on compared to common knowledge. In ancient greek times is was considered common knowledge, for example. $\endgroup$ – Rugnir Mar 15 '16 at 13:27

There's no way to answer this with any great confidence.


As @Rugnir has noted, the spherical moon and earth were well known already to the Greeks, and there is good reason to think that this was also known in early China and India. If memory serves, it is somewhat unclear whether the ancient Mesopotamians knew this. But in any event, a rotating moon would presumably not speed up this early discovery.

One thing is that the analogy between a rotating moon and the rotating earth might have led somewhat earlier to a strong preference for heliocentric models. These were in fact proposed quite early among the Greeks, but were so annoying to calculate that, in the absence of strong evidence in their favor, they tended not to be followed up effectively. Since at base Copernicus's proposal was a matter of advanced geometry rather than (for instance) algebra, it could have been developed earlier. And if there were a strong preference for such a model, it might well have stuck firmly enough for geometers and astronomers to work out the kinks (as did not happen in European history until relatively late in the 16th century and on into the 17th with Kepler).

In addition, because the moon rotates and thus alters its appearance, the use of lenses to examine its changing faces might have been of significant interest rather earlier than Galileo Galilei.

On the same point, the irregular image of the moon might have led to a much earlier undermining of the "perfection in the heavens" assumption that dominates Ptolemaic astronomy.


Cultures do tend to come up with notions about what the moon looks like, and develop mythological conceptions and descriptions. In Japan and parts of the Americas, the moon looks like a rabbit -- in Japan, it's a rabbit pounding mochi rice. In Europe, an old man's face is more common, though there are of course other notions.

I suggest that the changing faces of the moon would be classified and named, on the model of constellations. Within any given culture, a "rabbit moon" would differ from a "scorpion moon" or a "flower moon," or whatever. Each would then generate a range of mythological conceptions and stories.

These might in some cases have relatively concrete effects. For instance, it is quite common to ascribe both vulpine (wolf-like) and insane qualities to a full moon (thus luna-tics and werewolves). With a rotating moon, you might well get these kinds of ideas ascribed to particular faces of the moon rather than its phases.

More interestingly, I suspect you'd get both: a scorpion moon at the waxing half is understood to be especially dangerous, a full flower moon is especially calming, and so forth.

If I were doing this for a story, I'd probably come up with a bunch of images and concepts for the faces, then work out their notional implications at especially strong phases. But I don't know if you can get decent images of what the moon would look like -- of course, you don't have to use our moon.

Note that in many ways the moon will take on a considerably stronger role in astrological thought, but whether that's of use to you depends on whether you're planning to work out anything much in the way of astrology in the first place.


Probably the greatest cultural difference would be the undermining of the idea that the "Heavenly sphere" was fixed and unchanging.

Since much of the heavens do appear to be relatively fixed and unchanging, it was fairly easy for ancient priests and philosophers to believe that the heavenly realm is truly different from the mundane world that we live in. The planets and the Moon were obvious exceptions to the idea of a fixed and unchanging cosmos, but the planets became mythological beings, while the general consensus among the "educated" people of the ancient world was the moon was a perfect sphere, and we were seeing the reflection of the Earth on the Moon's face.

This sort of attitude tended to sharply divide science and religion/astrology, since the various rules and ideas that seemed to work in the mundane world were obviously not in play in the celestial sphere.

A rotating moon, on the other hand, isn't so easily explained. It is pretty obviously a world in its own right, and while the idea that there were other worlds did exist in ancient times, it was considered a very eccentric notion at best, and rapidly died out. With the example of a world visible in the sky visible to everyone, the idea that the planets might be other worlds would not be so difficult to accept, and the sharp boundaries between the heavens and the Earth would not exist (or be much harder to justify). Notions like "there are other worlds", a heliocentric solar system and that natural laws apply everywhere and not just on Earth would have a much greater base, and rather than a "Scientific revolution" we would have a much more gradual and possibly board based growth of science as the philosophical world view of most people.

Specific changes to history would be difficult to imagine, although it is probably safe to say that Hero of Alexandria isn't going to be inventing liquid fuelled rockets. More likely society and culture will not be so structured with a priesthood claiming divine and mystical powers not accessible to mundane understanding, since it is obvious to most people that "mundane understanding" applies everywhere. A more fluid social order is the most likely outcome, and oligarchies, republics and democracies will be more common and arrive earlier than in OTL.


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