What do you guys think of UFO's?

[Your Computer]

Even though i said the very existence of an alien visitor has a good chance of contradicting a lot of what we know about physics and therefore biology

So an alien from outer space accomplishing a goal of visiting our planet Earth from the far reaches of the universe wouldn't contradict not one thing that we know about physics or biology today, not even one of the premises you gave?

I only have to assume it correct as far as it is practical.

So, even though contradicted by the very existence of a far away alien lifeform, what we know about physics and biology today would still remain practical in explaining how the alien managed to get here from a solar system that would have required decades of travel or more based on our knowledge of theoretical space travel and how a species is designed to survive?