So Red Dwarf's been going away from Earth for three million years. Fair enough premise, but alas, the crew have come across Earth a fair number of times. Why aren't they there? Because it would ruin the plot and all, that's why. But let's go through when the crew actually could have returned, and why they didn't: Stasis Leak - the crew do go back in time, and also to the solar system! The ship is in orbit around Ganymede (which is where Kochanski and future Lister enjoy their honeymoon) so it wouldn't be too difficult for Lister, Rimmer and Cat to stay around (or Lister and Cat in any case, as we haven't established any hologram range issues). If the stasis leak remained (no idea if it did) then even Holly could have been brought through in bits and reassembled. I guess the reason why it doesn't happen (and probably why it doesn't happen in all these cases) is that future Lister tells them it doesn't happen (and probably future Lister from Future Echoes too). Backwards - yep, it's Earth, but it's in completely the wrong time period and going backwards. The Dwarfers couldn't really have survived (as shown in the book). Timeslides - can't leave the confines of the photo, but bizarrely you can affect time. Odd one. What if they found and mutated a picture of Earth (as seen from space), and projected it onto a surface big enough to fly Starbug through? We could just say the developing fluid went gunky. Tikka To Ride and Ouroboros - okay, this is the biggie. A machine that allows travel through time and space, which basically means the crew can Doctor Who all over the shop. They do a bit, then don't for some reason. Lemons - Earth again, but the wrong bit in history. See Backwards. Don't know how Rimmer or Kryten survived without the large amounts of electrical charge either would need. Ho-hum. Either way, it's a comedy. I can sort-of understand the various future Listers saying "oh it's your destiny" or something, but I'm pretty sure I'd say "screw that, I'm buggering off to Earth". Pretty sure these aren't the biggest plot-holes in the show.