Well, there are galaxies, and then there are galaxies. The nearest other galaxy comparable to our own is the Andromeda galaxy, whose distance away from us is about 20 times the size of our Galaxy. But major galaxies like the Milky Way and the Andromeda each have dozens of dwarf galaxy groupies, some of them barely more than large globular clusters. When someone makes an estimate like “one civilization per galaxy”, they don’t mean “one in the Milky Way, and one in the Saggitarius dwarf”. More likely, that would mean “one in the Milky Way and all of its satellite galaxies collectively”, or possibly “One each in the small galaxies, but a whole bunch in a heavy like the Milky Way”.
Yeah, and it’s headed towards us at 140 kps. In 3 or 4 billions years, we’re going to have a lot of stars to explore, or exploring us!
The closest galaxy to ours is the Andromeda Galaxy which is 2,900,000 light years away. The Milky Way Galaxy is only 100,000 light years across and it’s estimated the Solar System is about 26000 light years from its center. So were much closer to any system in our galaxy than to any system in Andromeda. The only extra-galactic formation that is closer to us than the center of the Milky Way Galaxy is the Canis Major Dwarf Galaxy, which orbits our galaxy and happens to be in our relative vicinity at about 25000 light years from us. The next closest formation is the Sagittarius Dwarf Elliptical Galaxy which is 88000 light years away from us.
I’ve heard that our radio telescopes are still just too primitive to pick up a message from another solar system. If there was a planet 20 light-years away that had exactly the same radio emissions as Earth, and we knew exactly where it was, I’ve heard that we still couldn’t detect any sign of intelligent life from radio emissions, even if we specifically searched for known Earth-type radio signals. If we can’t do that, then we have no chance of finding something unknown with our current technology.
And also headed sideways at an unknown rate. We can’t tell how long it will be until closest approach, or what the distance at closest approach will be, but it almost certainly won’t be a collision.
Thank you, but I know. Canis Major Dwarf still has a billion stars in it. Not much compared to our 200-400 billion, but still. 
What’s the difference between a dwarf galaxy and a ‘real’ galaxy?
How many of those worlds are going to be Earth-like? We’re going to be looking for worlds on which humanity can live unsupported, can live by means no more advanced than what we have on Earth.
Nor do we know yet that life is a miracle, or, I would say, a concatenation of circumstances unlikely to be duplicated. Perhaps every Earth-like planet that’s been around long enough has evolved intelligent life.
Given the history of humanity, I would suggest that any intelligent life on those planets had better watch out.
Where did you hear this? I don’t see why something like the VLA wouldn’t pick up intelligent signals from 20ly and much farther. Especially if we knew exactly where to listen.
Here’s a link with picture. I think you’re too pessimistic - next decade for sure, and maybe this one.
I’m starting to think, more and more, that the answer to the Fermi paradox is that the vast majority of intelligent species destroy themselves either before they attain interstellar travel, or shortly thereafter.
The development of interstellar travel necessarily depends on harnessing energy in ways that we haven’t yet thought of. We either need ways of producing currently unimaginable amounts of energy, or ways of understanding physics that allow us to do really incredible things with what amounts to far less energy. That knowledge could also be used to do some pretty disastrous things to ourselves.
The threshold for attaining sufficient energy and the knowledge to apply it to destruction is constantly being lowered. It seems quite possible that the knowledge and capability to destroy humanity will filter down to small enough groups that one of them will think it’s a good idea well before we have the capability to get off this rock.
For radio communications, perhaps all planets with intelligent life forms lie fairly far away from us, say 1,000 l.y., and would prefer to beam their signals to habitable planets where the responses would arrive in a reasonable time.
Civilizations with stl travel, even if close, may only want to visit us once every few thousand years. Perhaps the last time they came we weren’t interesting enough to contact, just observe.
Even if ftl travel is possible, starfaring races might value diversity, and too early contact would distort a race’s development. In my universe contact is forbidden before a race makes it to another star, since that only happens when a planet is unified and reasonably mature. For all we know they are waiting out there for us to get our act together.
I don’t know about that… The most plausible power source for a starship is a fusion reactor. But we’re already pretty good at using fusion power for destructive purposes; the necessary technological advancements are just for using it controllably. Sure, the research which leads to workable nonviolent fusion will probably also improve the effectiveness of fusion bombs slightly, but that just means we have one more weapon that nobody dares use.
I’ve heard similar, except I think it’s 30-40 LY beyond which, your radio signals are like pointing a flashlight at the sun; it’s just too hard to pick your light from all the background light. Also, there aren’t that many stars within 30-40 LY of us, and the odds of their transmitting/listening at the same time we are is pretty remote. They could have stopped listening a million years ago, or they’re not going to be advanced enough to listen to us for another million years, but 1,000 years from now we may decide to contain our communications to our own system, or move to a form of communication they don’t even know could exist.
Oh I hope so. Either one would be amazing.
I’m not too confident about it, though. I’m not even sure we’d be able to recognize the remains of past extraterrestrial life.
We ourselves could be past extraterrestrial life. I’ve read some scientists feel life on earth emerged maybe as much as a billion years earlier than it should have been expected to. If so, it’s possible earth got seeded with microbes from an older planet someplace.
This is called panspermia. The idea was laughed at only a few years ago but it’s starting to gain a lot of mainstream acceptance. What I’ve read in support of it makes a lot of sense.
IANAA, but lemme hazard a guess…unh, maybe…size?
Right, that’s the most obvious difference. Not to speak on behalf of RTFirefly, but I think the point was if you’re a galaxy, you’re a galaxy, big or dwarf. A star is a star, big or dwarf. If you’re a galaxy, you’re not a globular cluster, or simply a “formation.” There must be a cut-off between “some stars” and “a galaxy.”
I stated that our nearest galaxy is closer to earth than earth is to our galactic core, and certainly much closer than earth is to the other side of our galaxy. That the nearest galaxy is a dwarf galaxy doesn’t mean it isn’t a “real” galaxy. It’s got a billion stars. Give it some credit.
The strongest argument I’ve seen for panspermia lately is the discovery of bacteria living in the highest reaches of the Earth’s atmosphere. Since it’s clearly impossible for the bacteria to have made it all the way up there from the ground, the idea goes, they must clearly have originated from some other planet, instead.