People often ask, in regards to Numenera, how can it be that no one knows what happened to the "eight prior worlds", yet we somehow know that there were eight such worlds, no more, no less? Or: where did humans come (back) from? Or: why hasn't the sun rendered the Earth uninhabitable after a billion years? Humans are inquisitive; surely someone would have sought out the answers.
Well, one thing players will have to contend with is that most residents of the Ninth World just don't care about that kind of stuff. It has no obvious relevance to the daily struggle for survival. They may spend an idle moment wondering about it, but it will be rare for anyone to do anything tangible to follow up. "Humans are inquisitive," but not everyone is inquisitive about ancient history specifically. How many residents of our own world know anything about the fall of Constantinople or the Punic Wars or the Louisiana Purchase? These events have helped to shape the modern world in important ways, but most denizens of the modern world don't think about them much, or at all really, even though information about them is readily available. Ninth Worlders, it seems to me, have even less motive/means/opportunity to dwell on a past that would undoubtedly seem so far-removed, irrelevant, and "unreal" to them.
That said, the answers aren't so much unknowable as they are simply unknown. Assuming you are a GM, if your players want to go on some kind of adventure that may solve some of the vexing issues of the Ninth World's history, let them. Even if there is no official answer to the questions they are curious about, you can always come up with your own as GM. If players are allowed to "save" the world, they surely are also allowed to learn at least some of its history, in dribs and drabs from ancient texts or the occasional reclusive, likely insane, long-lived AI.
Some ideas: Perhaps the Ninth World is called that simply because the previous mega-civilization called itself the Eighth World, according to the most ancient texts we have. But in a fun plot twist, perhaps the "Eighth World" is called that for some other reason than literally being the eighth great civilization. Perhaps Earth was the eighth planet to be colonized by the mighty Varjellen Consortium about 2 million years ago (Varjellen dislike poetry, so maybe they are also uncreative when it comes to planet names). Or, perhaps the number 8 had some kind of symbolic or religious significance to the Eighth World culture and was never meant to be understood literally (representing the eight steps to enlightenment or something). Or-- and this is my favorite one-- perhaps "Eighth World" was a mistranslation of the ancient historical texts-- the Eighth World conquered not just the stars but other dimensions where even the laws of physics were different, and called itself the Eight-Dimensional World-Union. This was simplified to "Eighth World" by historians who didn't comprehend the notion of alternate dimensions.
Then the next civilization comes along and is like, well if they were the "Eighth World", we must be the "Ninth".
And, for me, to explain the reemergence of humans, my tentative head-canon (as opposed to my tentacled-head cannon) is that the (non-human) Eighth Worlders discovered some preserved human remains and reconstructed them on a lark, displaying the neo-humans in something akin to zoos. But eventually the humans rose up, "Planet of the Apes"-style, and brought the Eighth World to a violent end, ushering in a million-year dark age. (If that seems like an excessively long dark age, keep in mind that the humans of this dark age had terrible monsters to contend with that we didn't have to worry about during the medieval dark age, not to mention the enraged survivors of the Eighth World, making rebuilding difficult. And in any event a million is 0.1% of a billion.) Humans of the inter-World dark age didn't like to think about what they and their ancestors had done, and so didn't tell their descendants the specifics of what happened to the Eighth World. Eventually the Eighth Worlders were all dead (or so it is believed) and the whole unpleasantness was forgotten. It doesn't take long for the truth to be forgotten if no one wants to remember it. Much like the real world in that respect.
Additionally, there is an interesting place in the NWGB called the Kingdoms of the Dawn, on the opposite side of the mega-continent from the Steadfast, where they have never heard of this "Ninth World" or its eight-prior-worlds implication. That suggests that the Eighth/Ninth World thing may be mostly legendary. Or that the Dawn People may just have some kind of historical blindspot for some reason. Either way, it adds a new wrinkle to the question.
Well, one thing players will have to contend with is that most residents of the Ninth World just don't care about that kind of stuff. It has no obvious relevance to the daily struggle for survival. They may spend an idle moment wondering about it, but it will be rare for anyone to do anything tangible to follow up. "Humans are inquisitive," but not everyone is inquisitive about ancient history specifically. How many residents of our own world know anything about the fall of Constantinople or the Punic Wars or the Louisiana Purchase? These events have helped to shape the modern world in important ways, but most denizens of the modern world don't think about them much, or at all really, even though information about them is readily available. Ninth Worlders, it seems to me, have even less motive/means/opportunity to dwell on a past that would undoubtedly seem so far-removed, irrelevant, and "unreal" to them.
That said, the answers aren't so much unknowable as they are simply unknown. Assuming you are a GM, if your players want to go on some kind of adventure that may solve some of the vexing issues of the Ninth World's history, let them. Even if there is no official answer to the questions they are curious about, you can always come up with your own as GM. If players are allowed to "save" the world, they surely are also allowed to learn at least some of its history, in dribs and drabs from ancient texts or the occasional reclusive, likely insane, long-lived AI.
Some ideas: Perhaps the Ninth World is called that simply because the previous mega-civilization called itself the Eighth World, according to the most ancient texts we have. But in a fun plot twist, perhaps the "Eighth World" is called that for some other reason than literally being the eighth great civilization. Perhaps Earth was the eighth planet to be colonized by the mighty Varjellen Consortium about 2 million years ago (Varjellen dislike poetry, so maybe they are also uncreative when it comes to planet names). Or, perhaps the number 8 had some kind of symbolic or religious significance to the Eighth World culture and was never meant to be understood literally (representing the eight steps to enlightenment or something). Or-- and this is my favorite one-- perhaps "Eighth World" was a mistranslation of the ancient historical texts-- the Eighth World conquered not just the stars but other dimensions where even the laws of physics were different, and called itself the Eight-Dimensional World-Union. This was simplified to "Eighth World" by historians who didn't comprehend the notion of alternate dimensions.
Then the next civilization comes along and is like, well if they were the "Eighth World", we must be the "Ninth".
And, for me, to explain the reemergence of humans, my tentative head-canon (as opposed to my tentacled-head cannon) is that the (non-human) Eighth Worlders discovered some preserved human remains and reconstructed them on a lark, displaying the neo-humans in something akin to zoos. But eventually the humans rose up, "Planet of the Apes"-style, and brought the Eighth World to a violent end, ushering in a million-year dark age. (If that seems like an excessively long dark age, keep in mind that the humans of this dark age had terrible monsters to contend with that we didn't have to worry about during the medieval dark age, not to mention the enraged survivors of the Eighth World, making rebuilding difficult. And in any event a million is 0.1% of a billion.) Humans of the inter-World dark age didn't like to think about what they and their ancestors had done, and so didn't tell their descendants the specifics of what happened to the Eighth World. Eventually the Eighth Worlders were all dead (or so it is believed) and the whole unpleasantness was forgotten. It doesn't take long for the truth to be forgotten if no one wants to remember it. Much like the real world in that respect.
Additionally, there is an interesting place in the NWGB called the Kingdoms of the Dawn, on the opposite side of the mega-continent from the Steadfast, where they have never heard of this "Ninth World" or its eight-prior-worlds implication. That suggests that the Eighth/Ninth World thing may be mostly legendary. Or that the Dawn People may just have some kind of historical blindspot for some reason. Either way, it adds a new wrinkle to the question.