Well they don’t have absolutely nothing. We know how much it costs to get mass into orbit, we know the launch cadence we’re capable of, we know how long it take

Well they don’t have absolutely nothing. We know how much it costs to get mass into orbit, we know the launch cadence we’re capable of, we know how long it takes to build huge vessels like nuclear powered submarines and aircraft carriers, we have realistic proposals for propulsion techniques that could get us to our nearest neighbour. You could make limited extrapolations from these points to figure out how much it would cost and how long it would take to build a colony ship. That would tell you a bit about the conditions necessary to begin colonizing the galaxy and you’d be able to tell if those conditions were likely to occur in the near future. We know how long it took to colonize the Americas so you could adjust that data. That should give you both the rate at which you can create colony ships and how long it takes for a colony to reach the point that it can begin building them.