Depends on how big your antenna is.
We find conclusive proof of advanced alien civilization on a nearby exoplanet; what do we tell them?
Something like truth social speaking to twitter back and forth, perhaps with a dash of religion and mansplaining thrown in for comic relief? That would end well. Show our best, make them like us.
“Roll up your windows and lock the doors when you drive past us!”
Just lob a few neutronium bombs our way. Please!
They could reasonably consider trying to show only our best as attempted trickery. And I doubt we could trick alien anthropologists for long.
We come in peace and mean you no harm is the first lie we tell everyone, why stop now?
Even if nearby I don’t think we will be able to communicate much more than peek-a- boo I see you within our lifetime. It would take hundreds of years to have a conversation and we don’t have that kind of attention span.
If they’re that advanced, they probably know about countless other advanced civilizations out there. Why would they care that much about one more?
The more advanced a civilization gets, the less it tends to radiate because all that radiated energy is pure waste. We’re already radiating a lot less than we used to, because we’re using much more in the way of cables and directional transmissions and so on.
Developing an advanced civilization requires curiosity, and probably a good deal of competitiveness. So there probably would be something like alien anthropologists looking for new worlds to describe and understand.
If on the other side of the galaxy, the energy expenditure to communicate with us might be beyond what alien anthropologists can afford. But if “say, five light years away,” as specified in the OP, it won’t take all that much expenditure for them to study us.
In fact, the other side of the galaxy would be one of the worst possible places; we’d have the bulk of the Galactic Lens between us and them. We can observe other galaxies easier than we can the opposite side of ours; as in, “we can actually see them”.
I expect that actually finding them would be harder than sending a signal. The galaxy is huge, the number of stars vast, and any signals likely to be very hard to detect. Actually sending a signal is a comparatively simple, brute force issue.
withdrawn
I’d say “please help”. It seems very unlikely that they would be within mere millennia of our technological level. It’s far more likely that they will be vastly more advanced than us, or not an ETI at all.
If it’s the former it would be nice if they could use a minute fraction of their tech to completely change our world. Yes they could squish us like a bug but there was nothing stopping them doing that already.
that’s not the question buddy.
I just realized the problem with this. A lot of that everything is dual-use (civilian-military).
Someone may say that’s harmless because the other civilization is too advanced not to know about, say, the H bomb. But are they? It seems to me probable that they are more advanced than us in some areas but missed out in others.
Unfortunately, if the alien civilization is close enough (couple hundred light years?), future billionaire hobbyists could afford to send them everything, and one of them will. The prime directive is incredibly difficult to implement because all you have to do to negatively influence another culture is to notify them that something is possible. Then they’ll invent it.
Sure, it’s a risk. They could have bombed themselves back to the stone age before our lightspeed transmission gets to them as well. They could take what we give them and use it to create a hegemonic world controlled by a new technocrat class with what we send them.
By sending it all, the good, the bad, the ugly, maybe they’ll learn from our mistakes and success. Maybe it’ll kill them all. I’d rather be Prometheus, or, perhaps, the Serpent in the garden that offers them the knowledge of both good and evil. Anything we choose with our extremely limited knowledge of the other party is a risk. Given we have no practical way over that distance to establish effective real-time conversations (or any sort of question answer given the expected 10 year round trip on each pairing, it’s going to be tough. The OP is already assuming we’re somehow able to establish the communication despite that, so why not?
Again, given they’re an “advanced” civilization for us to confirm over a 5 LY gap, I did assume that they’d be able to identify us quite quickly, especially since they’d have our transmissions as a vector, but likely even without them. So the biggest possible cultural shock, that they’re not alone may (cultures vary after all!) have already happened.
See, that’s the thing. There’s nothing closer than about 4 1/4 light years, or about 40 trillion kilometers. After the star system in Alpha Centauri, there are about 9 stars roughly in the 6 to 10 light-year range. Even these relatively close neighbours are unreachable with any known technology.
We can pretty much rule out any extraterrestrial life anywhere within our own solar system. So I think we’re safe from aliens for the foreseeable future. There’s a real long-shot hypothesis that there could be life in the ocean under the ice of Europa, but I’m going to guess that it’s unlikely that fish will build spaceships and attack us.
Indeed. The best defensive approach against potentially hostile aliens is to inform them about nuclear weapons and how to build them, then wait for them to wipe themselves out. There’s a hypothesis that the discovery of nuclear energy may place an insurmountable upper bound on the lifespan of any civilization.
Even a large directional antenna won’t be of any help if the signal strength is low enough to be indistinguishable from the random radio noise in the universe and, if receiving just a few photons, from quantum noise.
So what is the question?
There’s just not much time in terms of technological development between them being less advanced than us, and completely unable to detect us at all. Radio telescopes were invented less than a hundred years ago, after all.
But in the other direction a civilization could easily be thousands or millions years older than us. Given that their advancement could be randomly anywhere on the spectrum between “less than a century behind us” and “anywhere between less than a century and hundreds of millions of years ahead of us”, it seems obviously the odds are very high that they are much more advanced.
Agree with all you’ve said about distances. But I didn’t make my point quite explicitly enough. So you launched off on a tangent from where I was going.
Since the OPs scenario is hypothetical, we can place the aliens and their star at any distance we want. Make them 30 light-days away if we want. As long as their star is far enough from ours that the two planetary systems are stable long term we’re both good. I admit I don’t know what that distance is for two Sol-like stars.
So the question was “How close / far apart could two compatible tech civs be and in fact be able to visit one another physically?” Assume no magic like warp drives.
Anything is distinguishable from noise, with enough data.
That depends on how much resources they’re willing to put into it, and how patient they are. With propulsion tech just a little beyond where we are now, and a mere few dozen million years, we’d be able to colonize the entire Galaxy.