What do you guys think of UFO's?

[BAndrew]

You didn't define that clearly enough.

And yes, it does, that's the meaning of knowledge being relative, Einstein himself said "We can't solve problems by using the same kind of thinking we used when we created them."Which is basically what knowledge being relative means in science and physics.

Well, this is a paradox because no matter what, there will always be a better explanation or theory about something, which doesn't make sense. So, you can't just say there is a better theory for sure.

The einstein's sentence you mentioned means that the solution to a problem comes from a different kind of thinking than the one it is used to create the problem. For example Zenos paradox. You cannot solve it by using the same logic. You must think of something else (that something else here is the use of time).