what is a realistic timeline for first contact, and how will it actually happen?
so we decode a message that we are pretty sure is of alien origin.
we send a message back and then wait a few decades or centuries.
we don't know how far away the origin of the message is. let's assume that it is less than 50 light years. that's still a round trip of 100 years. in other words it's a generational project, and we don't know if our first response is understood. we'll have to keep iterating until we can confirm that we are actually communicating. and then, the next step will be to try to understand each other.
with a round trip that long, even under the most optimal conditions just establishing a dialog based on say math is going to take a few centuries.
of course once we have a dialog, communication is going to speed up because then we can send longer messages.
but then it could still take anywhere from 500 to 1000 years before a common language is developed and we are able to share actual scientific and engineering knowledge.
once we reached that level of communication however, we can collaborate on developing FTL.
contrary to star trek, it was always my idea that FTL travel is not developed by the inhabitants of each planet/star system on their own, but only in collaboration across multiple such systems. maybe even more than two. driven by the desire to meet each other.
so from the point of the first received message it will be one millennium before we get to learn anything about and from these aliens, and another millennium before we can meet them in person.
and that's the optimistic projection. it could just as well take 10 times as long.