It is extremely unlikely that even if there has ever been an intelligent life there, it's at a similar civilization development stage to ours, today. It took ~4B years to get where we are today on this planet, but the age of our civilization is only about a hundred thousand years. In a few thousand years our civilization will advance so much that it will be completely unrecognizable (or cease to exist), so you're asking for either an overlap in two extremely short historical windows, on planets developing independently for billions of years, or you expect their civilization to be stuck at about our level for many millions of years.

Yes, so much this!

This is why things like SETI (and arecibo for finding ETs) make no sense. I compare it to using a telescope in 1850 to look for https://en.wikipedia.org/wiki/Flag_semaphore in space. The technology we have to send signals today will look completely pathetic to us when we look back on them in 50 years. Why would we expect ETs to use technology that we ourselves will abandon completely in the relative blink of an eye?

Well, for one, the doomed endeavors (if it actually is) are often worthwhile for the following reasons:

-The technology that stems from attempting to answer the problem.

-The unforeseen consequences - i.e. Maybe someday we'll reach technology that can detect signals in a more advanced way than we can currently and, through recording data from the past, have captured a signal years before that technology exists.

-How many people buy into lotteries despite having awful odds? The odds may be bad, but it's non-zero.

> The technology we have to send signals today will look completely pathetic to us when we look back on them in 50 years.

the technology doesn't matter, either yesterday, today or tomorrow it will still be electromagnetic waves which is what SETI is analyzing.

There is no reason to think we will be using grossly non-directional broadcast EM waves in 50 years for communication, and certainly not in 100 years. It's far more likely we will have extremely high bandwidth over very low distances, since that allows for far more bandwidth in aggregate (since you aren't interfering with other users on the same spectrum).

Or we might have moved on to laser (highly directional) or something nobody has thought of yet. I promise you we won't be using some kind of nondirectional, multi trillion watt carrier-based radio contraption that we would have to be using to be spotted by something like SETI on alien world.

Receiving a signal would be one of the more chilling things the Earth civilization can ever experience.

Good thing if these guys would be on approximately the same stage as we are, but chances are slim. An answer from someone who knows about radio for 1000 years in much more probable than from someone who knows it for 100 years, as we do.

Meeting the technologically more more advanced European expeditions did change the lives of the natives of the Americas, probably to the better, after a few centuries — if we ignore certain details.

Two possibilities exist: Either we are alone in the universe or we are not. Both are equally terrifying. - Arthur C Clarke.

Third possibility: we do not exist either.

I'm with Descartes on this one.

We're pretty close to being capable of launching a Bracewell-von Neumann probe if some billionaire had the urge to do so. But so far as we can tell, the galaxy is not already full of self-replicating interstellar probes. Where are they? The uncomfortable implication is that we are the first/only species to get this far.

The observable universe is very large. It would be easy to miss all the action.

From the traveller's perspective, due to time dialation, they would get there a lot faster than that (even if that much time would pass on earth).

At c/10 that's not a big factor, yet.

At that speed it is about seven minutes a day.

I also recently finished The Three Body Problem, we could get there in 500 years with the minor caveat that we are not killed in a dark forest strike sometime before then.

The dark forest strike is an interesting idea but there is no reason to actually believe that is how intelligent life on different planets would behave.

True. It's not based on any hard evidence but IMO the author made a persuasive argument for it.

We would get a response sooner if they communicated using more advanced technology

How? Any more advanced technology must still obey the laws of physics, and if we really are that wrong about the laws of physics, we'd have no way to receive such a message.

Well, there's stuff like wormholes, Alcubierre drives, etc. All problematic given our understanding, but a culture having made breakthroughs towards these might just show up on our doorstep one day.

There are ways to receive messages that don't require the recipient to have the tech. An uncontacted tribe in the Amazon can still be reached by megaphone, or plane.

To be fair, in that situation the tribe can be reached because they DO have the tech: ears, eyes, etc. So we're still contacting them via tech they have.

Wouldn't it be better to wait until we have superliminal travel to run away if they don't like us?

Or better yet, stay radio silent.

I think we're a bit too late for radio silence. Even if our comms are indistinguishable from noise at that distance, I bet our previously detonated nukes would have sent distinctive pulses across the near cosmos.

I wonder, does SETI look for signs of alien nuclear wars?

Someone else can figure out the math, but I'm pretty sure the energy from all of the nukes that have been detonated, especially if you only count the open-air ones, is minuscule compared to what the sun gives off. That would mask any possible detection. I wouldn't be surprised if just the solar radiation that the earth reflects is enough to mask the nuclear blasts, unless you're viewing them from right inside the solar system.

The spectral signature would be quite different.

In Pellegrino and Zebrowski's The Killing Star, it's the know-it-all attitude in Star Trek that seals our fate.

What kind of unique signs would a nuclear explosion create? Doesn't nuclear fission occur naturally?

Not really? Only in very rare exceptions. At least if you're talking about chain reaction fission.

Those gamma-ray bursts have to be coming from somewhere, I guess.

Gamma ray bursts are from interplanetary war? That's a terrifying thought.

My pet conjecture has always been that they're the interstellar equivalent of "Hold my beer and watch this..."

It is extremely unlikely that superluminal travel exists. It would fundamentally violate so many physical laws (including causality) that our prior for that should be low indeed.

If they have the power to come to us, they certainly have the power to find us, silence or not.