One thing to keep in mind is that ~80% of the universe is 'dark energy' and ~20% is 'dark matter'. The stuff we're made of is ~5% of the mass-density of the uni

One thing to keep in mind is that ~80% of the universe is 'dark energy' and ~20% is 'dark matter'. The stuff we're made of is ~5% of the mass-density of the universe. For the stuff you and I are made of, we have a pretty good clue as to what is going on, how it works, what the 'bottlenecks' are in terms of talking with other stuff that is like us. For dark matter, well... it falls down. That's about all we got. How it interacts, if at all, is a total mystery at this point. And there's about 4x more of it than of the stuff you and I are made up of (which is mostly in stars and black holes, at that!). Does it have phases? Can it have a temperature? If it can sustain something like life, what would that even be like? For dark energy... um... it falls up? Honestly, we got nothing at this point. We've not really even got an idea if it's a particle or a field or what. Most 'serious' physicists just ignore it as it's embarrassingly mysterious. If life could exist in something like dark energy, we'd be totally left out of any avenue to talk to it. At least with dark matter aliens you can send gravity waves at them. With dark energy ones, we have no idea at all. And dark energy has 16x the mass-density that we do. My point is that the majority of the universe that we know about today is just a total mystery. And we've only discovered this issue in the last 50 years or so. Meaning that in another 10,000 years, we're likely to have a completely different understanding of the universe than we have today. Like, so radically different that it's akin to the flat-earth model vs. general relativity. When it comes to alien communication, be patient. It's likely to be so outside our current understanding that it would baffle anyone currently alive; it will be literally unbelievable to you and I.