Niels Bohr said we are to stop asking questions of the sort. What is—what is light? What is an electron? We have to redefine the question itself. Instead we are to talk only of observed behavior. How are things observed to behave? So, for example, take the case of the electron in the T.V. tube. We can ask how the electron moves through space before it hits the screen. The answer is that it is observed to move through space like a wave. Or alternatively, we can ask how does it interact when it gets to the screen. How does it give up its energy? The answer is that we observe it to give up its energy as dots, tiny particles. Either we’re asking how it moves through space or how it interacts when it gets to its destination. We can’t be asking both questions at the same time. So, there’s never any call to have to use the concepts, wave and particle at the same time. Depending on what type of observation we’re talking about, it’s one or the other. It’s never both. Hence, the wave/particle paradox is solved according to Bohr but the solution comes at a price. The price is that we’re not allowed to ask questions of light or anything else outside of the context of us observing the light, or observing the electron, or whatever. Such questions are meaningless. Suppose for example, out there is empty space, there’s an electron on its own, not being observed, not interacting with anything. Under those circumstances, what is it? Is it a wave or is it a particle? No, you can’t ask that question. It’s meaningless. The very words, “wave,” “particle,” “electron,” even. They’re all words used specifically to describe observations. It’s a misuse of language to try to use those same words to describe what might exist in between the observations.

In effect, what Bohr was saying is that we used to believe that it was the job of the scientist to describe the world—the world as it is. Okay, and in order to do that you have to look at it through a microscope on a small scale or a telescope on the large scale, and experiment on it, but having done all of that—having observed it. What we eventually write down in a science text book is a description of the world whether or not you’re still looking at it, but Bohr—what Bohr says is, “No-no.” What you’ve written down here is a description of you looking at the world. What it’s like to interact with the world. It’s not about the world as it might be in itself. You’ve said nothing about that and never will.

Werner Heisenberg backed up Bohr and declared that it is possible to ask whether there is still concealed behind the statistical universe of perception a “true” universe in which the law of causality would be valid. But such speculation seems to us to be without value and meaningless, for physics must confine itself to the description of the relationship between perceptions. The relationship between observations. We can’t say anything about the world in itself—a world that is not being observed. What a shocking idea. But not surprisingly, not everyone goes along with it. Einstein in his discussions with Bohr for instances, Einstein maintained to his dying day that the goal of science remains what we always assumed it was—the descriptions of an objective world out there independent of whether we happen to be observing it. But it has to be said that eighty years—eighty years of fruitless argument and we’re still no closer to realizing Einstein’s dream today than he was then. And with each succeeding year it could be argued that it looks more and more as though Bohr was right. We really are up against the barrier of the knowable.