We said earlier that the job of science is to describe the world. In order to do this, we have to observe it to find out what kind of world it is. But having made the observations (done the experiments) what we write down in our physics textbooks is a description of the world itself, regardless of whether one happens to be observing it. Bohr, and other adherents to his so-called Copenhagen Interpretation of quantum mechanics, claimed that this was not so. What has been written down is not a description of the world at all, but a description of acts of observation made on the world. All our customary scientific terms such as energy, momentum, position, speed, distance, time, etc. -- they are terms specifically for the description of observations. It is a misuse of language to try and apply them to a world-in-itself divorced from the action of an observation. It is this misuse of language that leads to problems like that posed by the wave/particle paradox. Which is not to say that the world-in-itself does not exist outside the context of someone making an observation of it. Rather, as Werner Heisenberg asserted, all attempts to talk about the world-in-itself are rendered meaningless.
Not that there is anything new in this. The philosopher Immanuel Kant had long ago asserted that one could know nothing about the thing-in-itself. (So much for the death of philosophy.
Finally we ask whether the scientific enterprise, even in this more limited domain of describing only interactions with the world rather than the world itself, might one day achieve complete knowledge. I think not. After all, what do we do our science with? Our brain. But how come we have a brain? It is something that evolved in response to the need of our ancestors to find food, shelter, and avoid predators. It enabled them to survive to the point where they could mate and pass on their genes. The brain was part of their survival kit. Why therefore should anyone think that such an imperfect instrument should be capable of mastering all knowledge regardless of whether it has any relevance to survival?