I am thinking about various science fiction story lines involving various ways to move between stars in very short time frames, effectively being faster than light, but using concepts like quantum fields, warping space, or entering hyper space. Such speeds are necessary to justify humans moving between stars, we need to do so in a time frame that enables round trip commerce. The travel will occur when it is possible to go to some planet, do some business there, and return within a year or so of aging by all parties involved, those at either location and those who are traveling.
Alternatively, there may be multi-generational trips (may numbering in the hundreds of generations) can use feasible technologies to make the trip between stars. Such trips are likely one way trips with the purpose of colonization with no intention of communication back to the home location.
Both of these address the problem of traveling between stars in the context of a human lifespan. For realistic commerce to occur, we need to complete the round trip (including conducting business at the other end) during the span of aging at most a year but ideally just a couple days.
There is the alternative of using known technologies for transport at very slow speeds (relative to inter-stellar distances) but involving a species that aged much more slowly than humans. Assuming that such a species would age similarly to animals on earth, such as having a life involving about a billion heart beats, then such a species would live their lives at a much slower pace. A typical experience such as expressing a simple statement that for a human may be accomplished in a few seconds would take several months for this hypothetical creature. Given such a slow pace of life, they would age only a few weeks or days for the duration of a realistic form of propulsion to get between planets.
If such a creature did live, I would imagine it could only survive in space. If it were to land on either planet, the Earth or the other world, it would be unable to compete with (let alone negotiate with) the local creatures who need to live life at a faster pace.
Suppose that such a life form could exist, one that would live life at a far slower pace than we live on earth. They would be intelligent but their intelligence would be nearly impossible for us to detect or assess. Like asking a person a simple question and their taking a very long time for the answer, we would assume the person is retarded mentally. In actuality, such as species’s intelligence would be retarded, retarded in time. For the time spans involved in interstellar travel, their intelligence is just right for the task.
Again, there needs to be some commercial motivation to set about such trips. They would need to benefit from the visit, probably in some form of exchange that they can bring to another planet to complete the transaction, and still have plenty of life left afterwards.
How would such a space faring species living at a much slower pace interact with the locals at either planet?
In particular, how would they introduce themselves for the first time. That first communication may be to say “hello, please introduce us to your leader”. In their tongue, this simple statement may take months to articulate. Even if we tried to pick up some slow bandwidth message over the entire spectrum and over the entire sphere, we wouldn’t have the resources to do this. Without this communication, there is no hope for a meaningful trade.
The trade would be necessary because they would be unable to survive on the surface of the planet themselves, they’re responses would be too slow to compete with nature and if they are in any way nutritious they would be devoured before even noticing something happening. They need to trade.
They have the advantage of time. They can observe from a distance and learn about our lives in much the way we currently study chemical or atomic reactions occurring within nanoseconds. They will learn how to get our attention.
One way they can get our attention is to create an infectious and more fatal-than-normal virus and set it loose. A single virus would self replicate and spread. The numbers of infected and the severity of their outcomes would definitely get the attention of the leaders. Watching from afar, they would see who is actually in control, and more specifically who is most productive to interact with.
There remains still the message that this is not an ordinary virus. This one was introduced to send a message. The message would be in the virus itself or perhaps more cleverly in the statistical variations of outcomes among different sub-populations.
If a pattern does emerge where the pattern is clearly not random while also clearly not obvious from normal causes (such as preexisting health status), we may begin to recognize that there was an intelligent sender at the other end of this communication line.
How would we respond back? Hopefully, we’ll figure out some way that will not be as costly for continued negotiation.