ET's/Aliens yes or no?

[Dave]

Originally Posted by AquaPython

you are thinking along the lines of human (or close) technology. If there is a civilization that has conquered space travel, they are most definitely not using thrusters to rocket from star system to star system. We already recognize the plausibility of using worm holes / folding space, we just lack the technology and energy resources needed to harness them. That is just the theories that we have put together here in the last 20-30 years. such a civilization is most likely instantaneously moving about the cosmos.

I agree that the likelyhood of a long lasting spacefaring culture being limited to reaction thrusters being low. Something you've missed is they would almost certaintly have had to develop some sort of inertial compensator. Nobody likes going splat when the engines come on