> a system with 2 planets with intelligent lifeforms
That is an extremely unlikely scenario because both intelligent life forms would have had to evolve before either of them developed space flight. It took homo sapiens 4 Gyr to evolve in the first place but only 100 kyr to develop space flight after that. So the odds are slim to none.
Does intelligent life mean only human-level intelligence? If we found a bunch of chimp-like animals running around, would that count as intelligent life?
Sure, but our interactions with chimp-like intelligence on another planet are unlikely to be substantially different from our interactions with chimp-like intelligence on this planet. It only gets interesting when both are more or less evenly matched, and that is extremely unlikely.
And our interactions with same-level intelligence on another planet are unlikely to be substantially different from our interactions with same-level intelligence on this planet. We've seen this before when people from one continent encountered those from another. In fiction, we show (via projection) how we might treat other intelligent life forms (every accusation is a confession).
Spaceflight is not some law of the universe. Neither are ideas of human intelligence. Whales have bigger brains, they communicate, they have culture, they have traditions. Yet we write them off and relegate them with the rest of the animals below them and make no effort towards communication, pretending its impossible as we communicate with our dogs without thinking about it as such. We wouldn’t recognize intelligent life in the universe because we set the goalposts of intelligent life to be that of a science fiction readers expectation of what intelligent life ought to look like.
That is an extremely unlikely scenario because both intelligent life forms would have had to evolve before either of them developed space flight. It took homo sapiens 4 Gyr to evolve in the first place but only 100 kyr to develop space flight after that. So the odds are slim to none.