How credible would it be, for a sci-fi setting, that an empire of our own descendants might have (possibly after some disaster) "lost" the Earth in the sense of not knowing where it is anymore; ie. 100 000 years after man first walked on the moon, humanity spans a vast galactic empire, and the actual location of the homeworld is uncertain?
Would there be features of galactic cosmography that would help make that more likely? Less likely? How hard would it be to find again?
RPGPundit
Quote from: RPGPundit;356523How credible would it be, for a sci-fi setting, that an empire of our own descendants might have (possibly after some disaster) "lost" the Earth in the sense of not knowing where it is anymore; ie. 100 000 years after man first walked on the moon, humanity spans a vast galactic empire, and the actual location of the homeworld is uncertain?
Would there be features of galactic cosmography that would help make that more likely? Less likely? How hard would it be to find again?
RPGPundit
Any species that is expanding through the galaxy would have to have a sophisticated enough - and redundant enough - navigational function that this would be ridiculously unlikely. I say function rather than program because how people store and retrieve information is likely to evolve drastically over 100,000 years. I doubt even a concerted effort to wipe its location out would succeed.
-clash
If something happened that de-populated the Earth, either mostly or entirely, for an extended period, then it might slip out of the galactic mainstream.
Maybe something along the lines of a return of "Nemesis" that lets loose hundreds of comets on the inner solar system that pummel the planet, or a passage through a dust cloud along the galactic plane that dims the sun sufficiently to start an ice age and kills off most life on the planet. It would have to be something dramatic enough that the technology of the time couldn't reverse it.
If Earth stops being an important world because of these (or other) factors, it might eventually become "lost". For an added bonus, instead of having it be centrally located in the empire, have it be off on a fringe or something. No reason why Earth would HAVE to be the center of things over the lifespan of a galactic Empire.
Quote from: flyingmice;356527Any species that is expanding through the galaxy would have to have a sophisticated enough - and redundant enough - navigational function that this would be ridiculously unlikely. I say function rather than program because how people store and retrieve information is likely to evolve drastically over 100,000 years. I doubt even a concerted effort to wipe its location out would succeed.
This pre-supposes that technology expands (or at least fails to contract) indefinitely, and that all information is always stored forever. It also supposes that, in all the information acquired and maintained about everything ever for a hundred thousand years, there's a way to retrieve the one bit you want.
I think every single premise in there can be plausibly questioned, and any one could create the desired scenario.
You'd probably need a massive effort to wipe out stored data and people who know about the Earth's location. In short, you need a galaxy-wide Crusade, Inquisition, computer virus, and/or plague. Dark Ages all over again, where this particular bit of knowledge is lost or jealously protected by some.
That begs the following question: What do you find once you reach Earth?
Perhaps if we were dealing with a Alien Jumpgate type system and the Earth's gate was somehow destroyed?
Quote from: Halfjack;356534This pre-supposes that technology expands (or at least fails to contract) indefinitely, and that all information is always stored forever. It also supposes that, in all the information acquired and maintained about everything ever for a hundred thousand years, there's a way to retrieve the one bit you want.
I think every single premise in there can be plausibly questioned, and any one could create the desired scenario.
No, it doesn't, Brad. It posits that technology fails to significantly contract everywhere at once, and to the point where basic navigational data is discarded or destroyed in all places. To get to this point means that after spreading through the galaxy, all human settlements, and all non-human settlements which have this data from humans or their own explorations, are
simultaneously hammered back to a world-bound low-technology culture which cannot support data storage and retrieval for such important data as space navigation. I find this extremely unlikely. Otherwise it may be temporarily unavailable in certain areas at certain times, but it will infill from areas where it has been preserved once the area affected regains its space-faring culture.
-clash
Quote from: cnath.rm;356539Perhaps if we were dealing with a Alien Jumpgate type system and the Earth's gate was somehow destroyed?
That scenario was my first thought also, but even then you most probably know the astronomic location even if you won't be able to
reach it.
I think if there was some event that led to loss of information. Perhaps they hadn't had any need to go back to the earth for some time (is it still inhabited?). In this scenario the event in question would have probably led to the loss of other locations.
I do think this is a tall order. It would be like the British Empire forgetting how to get back to England. But it is space you are dealing with, and the timescale is much larger, so it is more plausible I suppose.
Well if you had an orginzation like in Dune that controls all the navigation. They are somehow destroyed, broken up, or what not by a war, or what have you. Then other people would start trying to re-explore the navigation routes. Perhaps there are reminants of the guild floating around. But no one individual has the whole picture of the routes.
Could be a good start on the concept of the lost earth.
Quote from: RPGPundit;356523How credible would it be, for a sci-fi setting, that an empire of our own descendants might have (possibly after some disaster) "lost" the Earth in the sense of not knowing where it is anymore; ie. 100 000 years after man first walked on the moon, humanity spans a vast galactic empire, and the actual location of the homeworld is uncertain?
Would there be features of galactic cosmography that would help make that more likely? Less likely? How hard would it be to find again?
RPGPundit
I think it would be highly unlikely that Earth could be "lost" like that.
I think it would be far more likely that Earth would become a fought over religious icon, like a planet-sized version of what Jerusalem is today.
Quote from: flyingmice;356527Any species that is expanding through the galaxy would have to have a sophisticated enough - and redundant enough - navigational function that this would be ridiculously unlikely. I say function rather than program because how people store and retrieve information is likely to evolve drastically over 100,000 years. I doubt even a concerted effort to wipe its location out would succeed.
Like Ur and Babylon? While knowledge of their existence persisted it wasn't until 19th century archeologists started digging that they were found again.
Barring some catastrophe the a likely scenario is that planet will still be inhabited but the fact that it was Earth, the cradle of humanity would be lost.
What it would take to do that is not any particular aspect of stellar cartography but a dark age where human knowledge is lost. Then later regained. If there are no dark ages then I agree with Clash that there is little chance that Earth's location would be lost.
Ur and Babylon's location were lost because of a multitude of changes that occurred in Mesopotamia leading the locations to be abandoned and then later forgotten. It has not happened to Rome or most of the Greek cities yet. But it possible the location of some of the older Greek City-states that were abandoned (Sparta for example) could be lost if a dark age fell on our civilization.
Even if Earth was lost there the idea that the region was humanity's cradle would likely persist.
Quote from: Ronin;356579Well if you had an orginzation like in Dune that controls all the navigation. They are somehow destroyed, broken up, or what not by a war, or what have you. Then other people would start trying to re-explore the navigation routes. Perhaps there are reminants of the guild floating around. But no one individual has the whole picture of the routes.
Could be a good start on the concept of the lost earth.
This would make sense. The smaller the redundancy ratio, the more likely data can be lost. My objections above are entirely based on massively redundant and widespread databases to begin with. Change that variable and all bets are off.
-clash
Quote from: estar;356606Like Ur and Babylon? While knowledge of their existence persisted it wasn't until 19th century archeologists started digging that they were found again.
Barring some catastrophe the a likely scenario is that planet will still be inhabited but the fact that it was Earth, the cradle of humanity would be lost.
What it would take to do that is not any particular aspect of stellar cartography but a dark age where human knowledge is lost. Then later regained. If there are no dark ages then I agree with Clash that there is little chance that Earth's location would be lost.
Ur and Babylon's location were lost because of a multitude of changes that occurred in Mesopotamia leading the locations to be abandoned and then later forgotten. It has not happened to Rome or most of the Greek cities yet. But it possible the location of some of the older Greek City-states that were abandoned (Sparta for example) could be lost if a dark age fell on our civilization.
Even if Earth was lost there the idea that the region was humanity's cradle would likely persist.
Ur and Babylon were lost because their locations were not plugged into a massively redundant and widespread database. Human memory is far to capricious to be depended on in such matters.
-clash
Battlestar Galactica?
Quote from: flyingmice;356613Ur and Babylon were lost because their locations were not plugged into a massively redundant and widespread database. Human memory is far to capricious to be depended on in such matters.
There nothing magical about high technology that makes it suitable for preserving knowledge over millenniums. It societal and culture changes that causes knowledge to be lost not the medium. It is lost because enough people cease to care about preservation.
Quote from: kregmosier;356624Battlestar Galactica?
Indeed, oh and Firefly, and perhaps Hitchhikers as well.
And the method of expansion from earth woudl need to be touched on.
I could see a situation where a high tech race took humans from earth to seed a planet/act as slaves/for fun/for deviant sexual purposes and those humans liberated themselves overcame their oppressors and set up a new civilisation. In some ways this is the BSG model as the Final Five led the exodus and so the humans were not fully savvy on the mechanics of the process.
I could also see a vast diaspora of relatively low tech ships from Earth to avoid some disaster resulting in separate cultures developing and some of those might hold no record of how they travelled and indeed might loose a lot of the tech that got them there if the single ship got damaged or whatever.
Quote from: estar;356625There nothing magical about high technology that makes it suitable for preserving knowledge over millenniums. It societal and culture changes that causes knowledge to be lost not the medium. It is lost because enough people cease to care about preservation.
If you are navigating space, this data is going to be preserved -
because it's navigational data - unless all societies using this knowledge simultaneously regress to a point where navigational data is no longer important and cannot be maintained. Given the immensity of that disaster, preserving the location of Earth is the least of their worries. I'd be shocked if they remembered earth at all.
-clash
Quote from: estar;356625There nothing magical about high technology that makes it suitable for preserving knowledge over millenniums. It societal and culture changes that causes knowledge to be lost not the medium. It is lost because enough people cease to care about preservation.
Interestingly enough there is an outlandish theory that the data was thus stored and that the database was called speach and that the technology was called writing
Quote from: jibbajibba;356629Interestingly enough there is an outlandish theory that the data was thus stored and that the database was called speach and that the technology was called writing
At least as interesting is the fact that there were languages and writing systems in our (relatively recent) past that are currently undeciphered. There are probably a hundred times more that are undiscovered.
Quote from: jibbajibba;356627I could see a situation where a high tech race took humans from earth to seed a planet/act as slaves/for fun/for deviant sexual purposes and those humans liberated themselves overcame their oppressors and set up a new civilisation. In some ways this is the BSG model as the Final Five led the exodus and so the humans were not fully savvy on the mechanics of the process.
I could also see a vast diaspora of relatively low tech ships from Earth to avoid some disaster resulting in separate cultures developing and some of those might hold no record of how they travelled and indeed might loose a lot of the tech that got them there if the single ship got damaged or whatever.
Both of these situations happened in StarCluster, but the second group never lost where earth was - the first group never knew - even though it was destroyed. Muslims still pray toward where Mecca was.
-clash
There's a disjunct here that's worth resolving.
If we're asking "is there a story in which Earth is lost that can be credibly sold to an audience" then I think the answer is obviously "Yes". We can invent a way that that might happen -- a set of criteria that would allow it and that are plausible.
If we're asking "does it seem likely that in a hundred thousand years there will be a galaxy-spanning empire of humanity that has forgotten Earth, as an extrapolation of what we know now" then the answer is probably "No, because the galaxy-spanning empire is already pretty unlikely and a half."
The second question is the least interesting (or perhaps the most) because it relies on an enormous number of unstated and vague personal premises. It boils down to "I think this". We can just state our thinks and be done. A poll would suffice.
The first, however, is soluble. We can explore the criteria that would allow that to happen and maybe even wind up manufacturing interesting (and useful, for those of us that play RPGs) settings in which it is true. Many different settings, maybe. We could get tools out of this.
Quote from: Halfjack;356633The first, however, is soluble. We can explore the criteria that would allow that to happen and maybe even wind up manufacturing interesting (and useful, for those of us that play RPGs) settings in which it is true. Many different settings, maybe. We could get tools out of this.
Actually, Pundit asked if it were credible, not if it were possible. Anything is possible, but to be credible, it needs to be likely enough that one can give credit to the story. One can make the possible credible by giving conditions which are not outlandish that would permit such a thing. One way is the retention of navigational data only by a select few, as in the Guild Navigators scenario mentioned above. That would work for me. Another is losing the gate access while retaining the astronomical location also mentioned above. That's credible too. If the particular scenario is true, then the concept becomes much more likely.
-clash
Quote from: flyingmice;356628If you are navigating space, this data is going to be preserved - because it's navigational data - unless all societies using this knowledge simultaneously regress to a point where navigational data is no longer important and cannot be maintained. Given the immensity of that disaster, preserving the location of Earth is the least of their worries. I'd be shocked if they remembered earth at all.
It seems to me the opposite is quite likely. Technology may easily advance to the point that you don't need to rely on thousands of years old data in order to navigate. i.e. If your navigation data is all lost, you just have to push a button and a few hours later you again have a complete and accurate star charts of the galaxy.
I agree with the prior poster that information isn't lost due to technological failure. After all, there is still plenty of cuneiform writing from Babylon that survives to the present day. Information is lost because of lack of will to keep it organized and accessible.
If technology progresses it becomes illogical that earth's location is lost. If technology were to some how regress after a point like in Warhammer 40k it's conceivable that the location of earth could be lost to a core body.
A more likely possibility is that some stigma gets attached to Earth due to some even so that it's name is stricken from the books and just becomes planet 57. Some where some lone computer in the pope's office may know that planet 57 is really earth but 50,000 years of that information being stricken from the general database would effectively lose it. 1,000 years would likely do it as well.
Of course another stock sci-fi one would be a galactic incident that causes the actual location of earth to change and it's no location lost. Massive dimensional sucking black hole or something equally sci-fi.
There is a modern example of data being irretrievably lost - data tapes from the Apollo missions stored by NASA that were improperly stored and/or the machines that could read them have long since been scrapped.
Not saying that would necessarily happen with data about where Earth is; just pointing out that technology is fine as far as it goes - its the people you need to worry about.
Quote from: flyingmice;356638Actually, Pundit asked if it were credible, not if it were possible.
-clash
In a 100,000 year time frame it is credible. Likely in reality? I doubt it. I think some sort of technological singularity would occur well before then that make our guess as useless as the speculation of a neolithic farmer would be make about what things would be like 10,000 years in the future.
I would say if you are creating a 100,000 history to make a RPG that approachable by the average gamers, Dark ages would have to be part of it to make it plausible. 10,000 years would be enough to make a couple of dark ages credible.
But absence dark ages then I don't see how anything can be lost in the future. Humanity will always be diverse enough so that somebody cares and the technology available to the individual sufficient enough to maintain and disseminate information to a wide audience.
Clash has a point about navigational data and that the location of Earth. It not like we are trying to preserve the music of the fourth most popular grunge band from early 90's Seattle. The topic is of wide enough interest that absence a dark age or a catastrophe it will be preserved.
You could have an interesting scenario where it's intentionally lost.
A colony encounters aliens, and gets into a war. Fearful that they'll lose, and that the aliens will carry on after destroying them, they erase all records relating to the location of the home world.
They do lose, but they're not entirely destroyed. Later, they rebuild and go back into space, but the records are gone, and knowledge of Earth's location with it.
Quote from: estar;356647Clash has a point about navigational data and that the location of Earth. It not like we are trying to preserve the music of the fourth most popular grunge band from early 90's Seattle. The topic is of wide enough interest that absence a dark age or a catastrophe it will be preserved.
Well, we being of Earth, of course we'd feel that we're important - and we'd like to imagine that we'll always be important. However, I don't think that's a given. In a hundred thousand years, it could be that humanity as a whole is only a minor species within the set of galactic inhabitants - and the exact location of its homeworld is no more important than the debate by the Akhvakhs over where their ancient capital was ten thousand years ago.
Moreover, it's not enough for information to be technically preserved in some way - it needs to be not just accessible, but authenticated and validated by some source. Just a few rounds of revisionist history is enough to put the question in doubt, and the digital age seems to be excellent at generating revisionist histories.
Quote from: jibbajibba;356627Indeed, oh and Firefly, and perhaps Hitchhikers as well.
And the Foundation series. Specifically, Foundation and Earth (http://en.wikipedia.org/wiki/Foundation_and_Earth). I'm surprised it hasn't been mentioned yet.
It's been awhile since I've read any of E.C. Tubb's Dumarest of Terra series, and I only ever read a couple of them, but I remember that this was the premise of that series -- that Dumarest was always trying to find his way back to his lost home-world, which was Earth. I don't recall what (if any) rationale was given for why Earth's location was lost -- does anyone else who's read these books remember? (And btw, any Traveller fan should try to read at least one or two of these because there's a ton of Traveller in them -- they're low-end pulp as literature, but it's still fun to see where the inspirations came from, just like a D&D fan reading The Dying Earth or Three Hearts and Three Lions).
Quote from: Werekoala;356530If something happened that de-populated the Earth, either mostly or entirely, for an extended period, then it might slip out of the galactic mainstream.
Maybe something along the lines of a return of "Nemesis" that lets loose hundreds of comets on the inner solar system that pummel the planet, or a passage through a dust cloud along the galactic plane that dims the sun sufficiently to start an ice age and kills off most life on the planet. It would have to be something dramatic enough that the technology of the time couldn't reverse it.
If Earth stops being an important world because of these (or other) factors, it might eventually become "lost". For an added bonus, instead of having it be centrally located in the empire, have it be off on a fringe or something. No reason why Earth would HAVE to be the center of things over the lifespan of a galactic Empire.
That's pretty much exactly what I was thinking: An interstellar-level disaster wipes out all human life on earth and makes the place uninhabitable for about 10000 years. Meanwhile, the colonies that were furthest from Earth are the ones that survive the most unscathed, and eventually, around one of these colonies, quite a distance further coreward than the Earth, there springs a new Galactic Empire of Humanity. Even more time passes, until eventually its known that the original homeworld was located somewhere in the spiral arm, but the exact location is not certain anymore, and the Galactic Empire is only now getting to the point where its beginning to explore those regions again, making new contact with some of the colonies in that area that survived (and usually ended up much worse off than the core-ward colonies did, some slipped into barbarism, lower tech, petty empires, weird cultures bred in isolation, etc). One of the goals now of interest for this new Human Empire is to find the missing homeworld, mainly for propaganda reasons.
RPGPundit
Quote from: JongWK;356536You'd probably need a massive effort to wipe out stored data and people who know about the Earth's location. In short, you need a galaxy-wide Crusade, Inquisition, computer virus, and/or plague. Dark Ages all over again, where this particular bit of knowledge is lost or jealously protected by some.
That begs the following question: What do you find once you reach Earth?
Ah, that's something for later on in the campaign.
RPGPundit
Personally, I don't think it's important to determine a credible reason why Earth is lost. I like the idea of the concept being shrouded in myth or legend.
Regards,
David R
One possibility could be that in an earlier dynasty of this new Human Empire, following the dark age that came with the collapse of the earth-based human empire, the new Colony-based imperial government had set itself up on a specifically anti-earth kind of ideological stance, ie. "the future is here now, on New Terra, the old Empire failed you, but this new Empire will flourish with a new beginning to create a truly Great and Bountiful Human Empire!", and that for political reasons it became anathema for several centuries to dwell on the question of "old earth", particularly if some of the earlier opposition to the Second Human Empire was focused on the myth of how great the old earth was and how these guys are just pretenders or something.
If it was politically dangerous for a few thousand years, that could explain how intentional imperial repression led to the loss of this data. Now, tens of thousands of years later, a new dynasty finds itself in a situation that is totally reversed, and they are the ones who are making political use of the old homeworld, and suddenly want to try to find it again.
RPGPundit
You know, if you are looking for a disaster that may result in Earth being lost, a Near-Earth Supernova (http://en.wikipedia.org/wiki/Near-Earth_supernova)could do the job.
Does Earth have to be in the same location that it is currently in ? If you have a myth of a displaced Earth, you could have an Earth Empire which is so strange, near alien, to the New Colonists once it's eventually found.
Regards,
David R
Quote from: jeff37923;356747You know, if you are looking for a disaster that may result in Earth being lost, a Near-Earth Supernova (http://en.wikipedia.org/wiki/Near-Earth_supernova)could do the job.
That was actually number one on my list of disasters, because it wouldn't just have fucked up earth, but also pretty much all of the older colonies that were the original "core" of the First Empire.
RPGPundit
Quote from: RPGPundit;356755That was actually number one on my list of disasters, because it wouldn't just have fucked up earth, but also pretty much all of the older colonies that were the original "core" of the First Empire.
RPGPundit
That's the #1 candidate for the loss of the Solar System in StarCluster. We never specified it, though. Thought it was more interesting left unstated. Only ships beyond 60 ly when the incident happened survived.
-clash
At least one game of mine deals with the idea that empires rise and collapse and that because of that cycle it is very likely that Earth becomes lost to the current cycle's Empire.
Although the current era might find it again. You can't assume that tracking becomes absolute. After all, even with all our "vast" technology to stone ages, and GPS tracking. We still get lost. Still lose our car keys. Etc.
Humans will likely remain fallible, and that being the case well losing ONE planet might not be that hard.
Quote from: RPGPundit;356523How credible would it be, for a sci-fi setting, that an empire of our own descendants might have (possibly after some disaster) "lost" the Earth in the sense of not knowing where it is anymore; ie. 100 000 years after man first walked on the moon, humanity spans a vast galactic empire, and the actual location of the homeworld is uncertain?
Would there be features of galactic cosmography that would help make that more likely? Less likely? How hard would it be to find again?
RPGPundit
That's basically the premise of my old timey (since about 1978) homemade setting for Traveller, or any sci-fi I run these days.
I was inspired by Larry Niven and a few metions of the Man-Kzin wars. In that universe humanity was slowly but surely getting its but kicked from system to system by the Kzin. You could imagine the Kzin made a point of seeking out other space faring cultures and enslaving them. When Earht saw through it's telescopes second (IIRC) Kzin fleet heading to conquer Earth (this is all STL) what would people do?
IMTU a similar encounter occured. The only rational thing to do was run, massive sleeper ships were made. It was an exodus. No records were kept or made of where the exodus ships were going in the hopes the Kzin couldn't follow. No details on the location of earth was included on the ships, folks were not coming back and it was feared other aliens existed just as dangerous as the "Kzin" out there. So the colonies don't know where Earth is, it's often a state secret even what general direction it may be. Of course no one knows what ended up happening to old Earth.
SO they didn't so much as lose Earth but intentionally wiped this navigational data and supress all other knowledge of where it may be, lest it fall into the wrong hands. The myth of Earth is also more politically maleable than a reality that refuses to cooperate.
BAH I SAY!!
Advances in technology will be met at every step with advances in bureacracy! We can lose a planet any time we like!
Before settling on how Earth was lost, you might want to consider why your PCs are looking for it.
Let's say you've got two campaign ideas-
One is a mad cap pan-galactic scavenger hunt for the E.S.S. Exodus' Navi Com and the fabled wherabouts of Old Earth contained within.
The other features a fleet of political refugees and romantics out to re-settle the Terran homelands against the wishes of the degenerate and corrupt Void Principate.
Personally, I think each scenario is suited to a different explaination as to why Earth has been lost. In someways it might be easier to work back from your campaign's premises.
And if Earth having been lost is just a bit of background fluff for your game, then I think you can safely gloss it over with 'shrouded by the mists of time' and 'subject to thousands of myths and rumours.'
Quote from: David Johansen;356799BAH I SAY!!
Advances in technology will be met at every step with advances in bureacracy! We can lose a planet any time we like!
So very very true.
Quote from: David R;356748Does Earth have to be in the same location that it is currently in ? If you have a myth of a displaced Earth, you could have an Earth Empire which is so strange, near alien, to the New Colonists once it's eventually found.
Regards,
David R
Spot on! Earth could have moved. Hell the population could have found a technology that turned the entire planet into an interstellar craft. Then got lost.
Exactly, the Earth would have to be moved; the Sun would be pretty much impossible to lose, and once you find that, finding Earth wouldn't be so tough.
Every colony would almost certainly know where 'our' Sun is, or was at some point, and could almost certainly see it with telescopes...not that much technology invovled for that, so even if civilization collapsed and 'navigational data' was lost, dead reckoning would still work.
So, best credible bet for losing the Earth would be for some technology existing for moving it. It could possibly entail moving the Sun, too, but eventually that 'new sun' popping up, especially a yellow sun with a spectrum exactly like the one for Earth, would probably be a tip-off, although it might take time (depending on how many light-years away the moved Sun is from the nearest colony with decent telescopes).
Quote from: RPGPundit;356523How credible would it be, for a sci-fi setting, that an empire of our own descendants might have (possibly after some disaster) "lost" the Earth in the sense of not knowing where it is anymore; ie. 100 000 years after man first walked on the moon, humanity spans a vast galactic empire, and the actual location of the homeworld is uncertain?
Would there be features of galactic cosmography that would help make that more likely? Less likely? How hard would it be to find again?
RPGPundit
The Empire would have had to have moved onward and outward, abandoning old borders as they went. With limitless wealth among the stars, the capital would have to keep moving, and the places left behind would be forgotten after a time, especially with rapid expansion and poor record keeping.
The easiest way to lose the location of something is to change the navigational references. If the future uses something like pulsar navigation, have some disaster change the local pulsars. Even better if the Earth isn't visited for a few thousand years and the change is gradual. Even if someone pulls the data from an ancient database it's no good anymore.
You guys have all given me some very good ideas to consider; a conversation the other night with my gaming group gave me some more stuff.
Obviously, all of this is in preparation for my Starblazer campaign.
RPGPundit