Could SETI (Search for Extraterrestrial Intelligence) find extraterrestrial civilization?

Today there are no officially confirmed contacts with extraterrestrial civilizations. There are suspected artificial-looking signals that source could be something that we don't know. The signals happened only once. And that makes determining those signals' origin impossible. So the WOW! and BLC-1 signal's origin remain unknown. The thing that those signals happened only once is remarkable. The natural reasons should cause that signals to happen more often than just once. 

But if the sender of those signals were some civilization, we must ask why they used those signals only once. Were those BLC-1 and WoW!- signals some kind of highly packed and encrypted data transmissions that some mission is done? But are the senders of those messages or signals living alien creatures, automatic probes, some kind of military operatives, or private organizations? And what was the purpose of those signals that are the most mysterious cases in history? 

That is one of the biggest questions in history. SETI is searching for intelligent civilizations by using radio waves and spectroscopes. The first one is searching radio broadcasts of hypothetical alien civilizations. And the second one search for things like pollution that hypothetical civilizations are creating. But the problem is that SETI has no right to listen to synthetic radio frequencies. 

And the use of mass spectrometers requires that the alien race uses similar combustion engines as we use. Things like sulfur compounds can form for other reasons than in combustion engines. 

And things like burning forests are not the same thing as intelligent civilization. So even there is chlorophyll on some planets. That doesn't mean that there is something else. Than bacteria on that planet's surface. So all creatures in the universe are not intelligent. But otherwise thinking, the bacteria can also be intelligent. The neurons can hybridize with bacteria. And that thing means that there could be intelligent lifeforms that are far from creatures that are living on Earth. 

The problem is that also space probes are shown that searching intelligent alien civilizations is more difficult than nobody thought. Those probes that are using the gravitational sling to push them to the trajectory to outer solar systems would not find intelligent lifeforms even from Earth. Of course, those probes saw city lights and other kinds of things. 

But otherwise, they didn't find signs of life on our planet. The problem with exoplanets is that they are far away from us. And we cannot separate cities from those planets. Things like brightness measurements could tell if the planet's dark side is too bright. And that thing can help to make conclusions. That there could be alien cities. But that requires very highly accurate measurements. 

Confirmation of that thing is very difficult because there is needed to measure the planet's albedo. And then calculate what albedo on the planet's dark side should be. Then telescopes should measure the real albedo of that planet. But things like flashes of lightning and volcanic actions can cause the planet to be too bright. So that method gives a tip that somewhere could be planets. 

When we are searching for extraterrestrial civilizations, we must understand one thing. Other planets are not Earth, even if they look like Earth. That means alien species might have green skin that makes their skin photosynthetic. But we must realize that aliens might not have a similar culture as we have. 

Or those aliens might not live on a planet that is comfortable for us. For them, their home planet is paradise. This means that those hypothetical aliens might not be anything, that we can even imagine. 

And as I wrote earlier, "do you speak extraterrestrial"? That thing means that maybe we are already heard alien transmissions. But we just cannot recognize those transmissions. That means we might have a language barrier between us, and hypothetical aliens. And that means that we or they don't recognize the data. 

That those civilizations sent and the reason why we cannot recognize those transmissions can be they are highly encrypted. That means those transmissions are not meant for us. 

Or we cannot just hear those radio transmissions for some other reasons. One of them could be that a hypothetical alien race would communicate by using quantum entanglement. Or they send their data through wormholes. 

But the biggest problem with the SETI (Search for Extraterrestrial Intelligence) program is that maybe we are listening wrong radio frequencies. 

SETI listens to the hydrogen alpha-emission line frequency. The more promising synthetic wavelengths are prohibited. Because of the information security. 

That frequency is the worst choice for searching artificial radio signals. The synthetic frequencies are better because there is less disturbance from cosmic radio background as hydrogen alpha line. There is the possibility that the cosmic radio background covers all artificial signals below them. 

https://bigthink.com/starts-with-a-bang/seti-detect-earth/

https://en.wikipedia.org/wiki/Albedo

https://en.wikipedia.org/wiki/BLC1

https://en.wikipedia.org/wiki/Wow!_signal