In science, nothing is ever finally, once and for all, settled, as in, no new evidence could require a new theory. But the atomic theory of matter is pretty well established. The heliocentric theory of the movement of the planets is pretty well settled. Newton's theory of gravity turned out to be wrong, but it was so nearly right that at ordinary speeds and for ordinary masses and densities, the difference between that theory and what is observed requires meticulously calibrated equipment and refined calculations to tell the difference.
To say that "nothing is settled" is to throw out the window the whole idea of learning about nature from observation and reflection.