Life needs some kind of chemistry that doesn't lock up into compounds so stable they're hard to crack apart, but allows compounds stable enough to build structures.
Carbon, hydrogen, oxygen, and nitrogen are suck a system. That's why organic chemistry is a thing. There aren't that many families of elements with that property.
Ammonia and silicon based life have been suggested. But none of the alternatives have very promising chemistry. See [1]. Life is probably stuck with CHON, in the "goldilocks zone" where water exists as a liquid.
We now know that planets are not rare. Many extrasolar planets have been discovered. A few are promising. The systems with known extrasolar planets might have smaller, more interesting planets, too small to be detected at interstellar ranges.
But stars are a long way away. Unless FTL is possible (which it probably isn't, because causality would break), the most we can hope for is someone to talk to by radio or something similar.
See the Drake Equation.[2] There's been progress on firming up the numbers since the 1950s.
CHON are also very common in the universe. Most proposed alternatives (not all) depend on things less common. This doesn't rule them out but it makes the odds worse.
Radio communications between tween solar systems require more energy than we have. We couldn't detect earth level civilizations in the nearest solar system (which probably doesn't have earth like life) even if both of us by chance aimed at each other at the correct time.
> Radio communications between tween solar systems require more energy than we have.
Supposedly, the Arecibo radio telescope, before it collapsed, could in theory communicate with a similar setup across most of the galaxy. The dishes would have to be aimed at each other.
I will admit to not being a RF engineer, but I've heard the claim from people who seem to know enough about astro physics that I tend to believe it. I know enough about physics (the inverse square law) to not doubt the claim. Now if you said this could have reached the nearest stars I'd be more inclined to believe you, but the galaxy is a large place.
> before it collapsed
This is a real problem - communication implies two-way, or at least intentional one-way. Across light-years of the galaxy anything that doesn't last for 200,000 years (or at least close to that) can't communicate. Arbitrary advanced technology has only detected life advance enough to detect their signals out a few light-years (assuming they care to look), and then they need to get a return signal back to us (again assuming they care, and we are looking)
Faster Than Light (FTL) isn't needed for interstellar travel. A cosy 0.01c would cross the distance between Sun and its closest neighbour (Proxima Centauri) in ~425 years. Less if we wait for it (or another star) to make its closest approach.
Further-away stars would take longer but on the flipside you have many more candidates as destination.
TLDR; any spaceship that can be kept operational for a few centuries or millenia, while travelling at a modest fraction of c, would allow space-faring intelligent life to meet alien life in person, as long as it is 'nearby' (compared to crossing the Milky Way for example).
Not saying that's easy! Or that alien life is nearby. But possible.
Life needs some kind of chemistry that doesn't lock up into compounds so stable they're hard to crack apart, but allows compounds stable enough to build structures. Carbon, hydrogen, oxygen, and nitrogen are suck a system. That's why organic chemistry is a thing. There aren't that many families of elements with that property. Ammonia and silicon based life have been suggested. But none of the alternatives have very promising chemistry. See [1]. Life is probably stuck with CHON, in the "goldilocks zone" where water exists as a liquid.
We now know that planets are not rare. Many extrasolar planets have been discovered. A few are promising. The systems with known extrasolar planets might have smaller, more interesting planets, too small to be detected at interstellar ranges.
But stars are a long way away. Unless FTL is possible (which it probably isn't, because causality would break), the most we can hope for is someone to talk to by radio or something similar.
See the Drake Equation.[2] There's been progress on firming up the numbers since the 1950s.
[1] https://en.wikipedia.org/wiki/Hypothetical_types_of_biochemi...
[2] https://en.wikipedia.org/wiki/Drake_equation