ISTR in the last year or so some prominent radio astronomer suggesting that radio and TV signals from Earth don’t make it much beyond Pluto’s orbit, if even that far, after all.
I gotta to the bathroom
Declan
“Hello, Mr. Friendy-Looking Alien, I’m lost and I was wondering if you could please tell me how to get back to Eart…”
ZAPPPPP
Holsters ray-gun. “Hey, Quartzog, that’s another of those pesky earthlings got past the quarantine zone. Better fumigate their planet after all, I guess”
Web Page Under Construction Heres the pale blue dot photo 4 billion miles away from earth .by Voyager.
On the upside, everyone you hated would be dead, too.
well, assuming that you are not more than about 100 light years from earth, and your hosts have sensitive radio receiving equipment on board you could use radio direction finding techniques to plot a heading to the planet. Which brings to mind another question: If indeed you could locate a signal and head in a straight line in its direction, it would point to where the earth was 100 years ago. How would you compensate for “windage”?
“go four parsecs thataway and then hang a left where Altair IV useta be”
It’s possible, and indeed routine, for astronomers to measure the movements of stars and be able to predict where they’ll be in the future. First they measure its blue/red shift, which tells them how fast the star is moving towards or away from us. Then they plot the star against background stars over a period of years. That gets its proper motion. The two combine to give the relative velocity of the star to that of the sun[sup]1[/sup]. Presumably the aliens have done the same for stars as well, so they could predict the future location of the sun.
[sup]1[/sup] You subtract off movements (rotation, revolution) of the Earth from the blue/red shift, since those will change depending on the time of night and time of year. It’s also best to measure proper motion at about the same time each year, so as to eliminate parallax shifting.
Hm. I think I would make sure to carry these three-dimensional laser-etched glass paperweights. Bathsheba Sculpture - Laser Crystals Quote from the Star Map product page: “Don’t Leave Earth Without It!” 
(I’d also bring along the one with the 100-megaparsec scale, just in case I get really, really lost.)
For the sake of the argument, let’s assume our laptop would get fried in the hyperspace ion storm that stranded us. But I’m sure the friendly aliens can provide us with a local copy. Only problem, you somehow need to know that you want to get to “Pgxofnark Qz’ilb13 zeta √236°97.22”. 
I for one would not entrust my only means of getting home to such delicate equipment. You know how it is. The batteries always die at the crucial moment. And it’s difficult enough buying replacement parts on Earth. Now imagine having to search on an alien planet for a power adapter that works with your particular model. Even if the shop in the next star system has it available on special order, the shipping costs would be a killer.
Celestia is a fascinating piece of software, though. I tried it out some time ago, and if there’s one thing I learned, it’s how freakingly easy it is to get absolutely, fatally, totally lost. Even just a couple of lightyears away from home. Whoa, space is big. And this huge galaxy of ours is just an itsy-bitsy part of it… (Anyone else feel like having a piece of fairy cake right now?)
Fair enough, but with my luck, I’d return only to find out that an evil galactic empire was created by billions and billions of descendants of everyone I hated.
The problem with the spoiler solution there is that they would have had to have been here once before, and at the exact time the picture was taken. Its an AWFULLY big galaxy, and if you had even 1/1000th of it mapped, you would be doing pretty damn well. I dont think you could depend on that one. It needs to be a way to find the planet without EVER having been here, or even remotely near here, before. And NO local time part or language references. Gotta be universals.
Mr. Adams is one of my favourite authors of all time, but I think he botched the Titanic solution big time.
No, they just need to have a detailed 3-d map of stars in the Galaxy and a heck of a lot of computing power. Neither of those seems particularly implausible for an interstellar civilization.
Technically, the book was written by Terry Jones. (No idea if the plot line with the photo occurs in the original computer game.)
Well, depends on how you define how much is mapped. Far as I know, we’ve mapped all stars above a certain brightness throughout our entire visible galactic volume. And we haven’t even remotely been near anywhere! (Well, except “here”.)
Maybe… Instead of focusing on detailed maps or trying to find specific fixpoints: Let’s calculate a three-dimensional Fourier transform of the star density around us. Memorise this histogram, or engrave it, tattoo, whatever.
This sort of data could be roughly fitted to any alien starmap like a fingerprint. It should be rather robust against distortions caused by time. Best thing, this would work at any scale! From our solar neighbourhood to superclusters. Where the frequency distribution fits, you’ll find our Sun at the centre.