4 ms·

extragalactic travel seems to be a really dangerous and difficult prospect. The journey will take millions of years (assuming no FTL travel), and there's basica

extragalactic travel seems to be a really dangerous and difficult prospect. The journey will take millions of years (assuming no FTL travel), and there's basically nothing in between. Even if your species is immortal or something, there's serious risks. You need to bring everything to need for the journey, including energy, because there aren't any stars you can stop at along the way to gather solar energy. You'd have to be very careful planning things so you don't wind up stranded partway.

pavel_lishin 10y ago
I think that when they say "intergalactic", they're not referring to ships crossing between galaxies - they just mean that the signals we're detecting (which may be light-sail 'engines') come from outside the Milky Way. The ships themselves could just be cruising between stars within those galaxies.
- openasocket 10y ago
  Well, now I feel dumb. I should have read beyond the abstract before commenting!
riskable 10y ago
If you're effectively immortal why would you want to hang around the same place forever? You wouldn't. In fact, you might hope for "something to happen" along a 100,000-year trip just to shake things up a bit! Also, don't assume that alien life is like ours. It could be many orders of magnitude more efficient and in all likelihood isn't even biological in nature if they've reached the point where a million-year journey is feasible. It could just be a bunch of AIs constantly re-making themselves from resources they pass by as they coast through the universe. They might not even have a destination! They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by. Lastly, in regards to energy: Why assume solar? Once you've reached speed you're not going to slow down much. Just leave the sails open to protect your craft from debris. I'd also expect a nuclear battery in such a craft to power on-board components. There's plenty of radioactive material in space to draw from for renewal as well. You also don't have to worry about disposal! Just toss it towards the nearest star system or asteroid belt and get a bit of thrust out of the action :)
- openasocket 10y ago
  I was talking about traveling between galaxies, my understanding is there's essentially nothing between them: no asteroids to mine. So you'd need to bring everything you might need in advance. But maybe I'm wrong, maybe there is a decent amount of debris floating between galaxies? > They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by. Whenever I think of what an advanced civilization would look like, I picture something like this (though not necessarily just machines). Something semi-nomadic, an entire civilization of ships in a big fleet, wandering together through the galaxy, stopping at various systems to gather some resources or explore the planets. Maybe the fleet breaks up and goes in different directions for a time, and rendezvous later.
  - Arizhel 10y ago
    >I was talking about traveling between galaxies, my understanding is there's essentially nothing between them: no asteroids to mine. So you'd need to bring everything you might need in advance. But maybe I'm wrong, maybe there is a decent amount of debris floating between galaxies? The current thought now is that there's likely quite a few "rogue planets" out there, and other asteroids that haven't gotten captured by a star. However, the density of such things is likely to be so low, and you won't know until you get there what they're composed of, so it seems like a bad idea to plan a trip assuming you're going to stop at a bunch of asteroids and rogue planets to pick up supplies; you'll easily make your trip far, far longer. Don't forget also the big problem in long-distance space travel is speed. If you want to get to a particular star system, you need to get up to speed and stay there until you're ready to decelerate. You can't afford to slow down and stop at a bunch of rocks along the way, and you'll be going far too fast to capture the small ones. Most of your fuel will be used in acceleration and deceleration, so you can really only do that once most likely. >Whenever I think of what an advanced civilization would look like, I picture something like this (though not necessarily just machines). Something semi-nomadic, an entire civilization of ships in a big fleet, wandering together through the galaxy, stopping at various systems to gather some resources or explore the planets. Maybe the fleet breaks up and goes in different directions for a time, and rendezvous later. That doesn't sound like an "advanced civilization" at all, that sounds like a nomadic gang. An advanced civilization will value stability, and stay on their home planet(s) where all their infrastructure is located. They may very well send out exploratory missions, but those nomadic wanderers will not be the civilization itself, just one small part of it.
kamaal 10y ago
There was this movie called 'Oblivion', one of the concepts suggested in the movie was- Interstellar travel being so hostile for biological life only real and practical way of ever encountering a life form would be in the form a machine/AI. You don't need to travel in your biological bodies. You can upload your brains to the AI and then have the machine basically run forever. The machine becomes your universe, and it figures out how to best survive in the universe(Mine planets, asteroids, prepare better versions of it self etc etc)

pavel_lishin 10y ago

I think that when they say "intergalactic", they're not referring to ships crossing between galaxies - they just mean that the signals we're detecting (which may be light-sail 'engines') come from outside the Milky Way. The ships themselves could just be cruising between stars within those galaxies.

openasocket 10y ago
Well, now I feel dumb. I should have read beyond the abstract before commenting!

riskable 10y ago

If you're effectively immortal why would you want to hang around the same place forever? You wouldn't. In fact, you might hope for "something to happen" along a 100,000-year trip just to shake things up a bit! Also, don't assume that alien life is like ours. It could be many orders of magnitude more efficient and in all likelihood isn't even biological in nature if they've reached the point where a million-year journey is feasible. It could just be a bunch of AIs constantly re-making themselves from resources they pass by as they coast through the universe. They might not even have a destination! They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by. Lastly, in regards to energy: Why assume solar? Once you've reached speed you're not going to slow down much. Just leave the sails open to protect your craft from debris. I'd also expect a nuclear battery in such a craft to power on-board components. There's plenty of radioactive material in space to draw from for renewal as well. You also don't have to worry about disposal! Just toss it towards the nearest star system or asteroid belt and get a bit of thrust out of the action :)

openasocket 10y ago
I was talking about traveling between galaxies, my understanding is there's essentially nothing between them: no asteroids to mine. So you'd need to bring everything you might need in advance. But maybe I'm wrong, maybe there is a decent amount of debris floating between galaxies? > They could literally just be a bunch of machines that "live" in space. Floating around from place to place, grabbing resources from asteroids as they go by. Whenever I think of what an advanced civilization would look like, I picture something like this (though not necessarily just machines). Something semi-nomadic, an entire civilization of ships in a big fleet, wandering together through the galaxy, stopping at various systems to gather some resources or explore the planets. Maybe the fleet breaks up and goes in different directions for a time, and rendezvous later.
- Arizhel 10y ago
  >I was talking about traveling between galaxies, my understanding is there's essentially nothing between them: no asteroids to mine. So you'd need to bring everything you might need in advance. But maybe I'm wrong, maybe there is a decent amount of debris floating between galaxies? The current thought now is that there's likely quite a few "rogue planets" out there, and other asteroids that haven't gotten captured by a star. However, the density of such things is likely to be so low, and you won't know until you get there what they're composed of, so it seems like a bad idea to plan a trip assuming you're going to stop at a bunch of asteroids and rogue planets to pick up supplies; you'll easily make your trip far, far longer. Don't forget also the big problem in long-distance space travel is speed. If you want to get to a particular star system, you need to get up to speed and stay there until you're ready to decelerate. You can't afford to slow down and stop at a bunch of rocks along the way, and you'll be going far too fast to capture the small ones. Most of your fuel will be used in acceleration and deceleration, so you can really only do that once most likely. >Whenever I think of what an advanced civilization would look like, I picture something like this (though not necessarily just machines). Something semi-nomadic, an entire civilization of ships in a big fleet, wandering together through the galaxy, stopping at various systems to gather some resources or explore the planets. Maybe the fleet breaks up and goes in different directions for a time, and rendezvous later. That doesn't sound like an "advanced civilization" at all, that sounds like a nomadic gang. An advanced civilization will value stability, and stay on their home planet(s) where all their infrastructure is located. They may very well send out exploratory missions, but those nomadic wanderers will not be the civilization itself, just one small part of it.

kamaal 10y ago

There was this movie called 'Oblivion', one of the concepts suggested in the movie was- Interstellar travel being so hostile for biological life only real and practical way of ever encountering a life form would be in the form a machine/AI. You don't need to travel in your biological bodies. You can upload your brains to the AI and then have the machine basically run forever. The machine becomes your universe, and it figures out how to best survive in the universe(Mine planets, asteroids, prepare better versions of it self etc etc)