I think the left side of the Drake equation is pretty challenging too. If we assume that faster than light travel is impossible (which is likely) and all galact

I think the left side of the Drake equation is pretty challenging too. If we assume that faster than light travel is impossible (which is likely) and all galactic civilizations are subject to the tyranny of the rocket equation, then it’s quite likely that there are no alien spaceships wizzing around, even if our galaxy is full of intelligent life forms. And then our best way of detecting advanced alien life forms is through direct observations of remote star systems, a field that is in its infancy at best.