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