The uncertainty principle “protects” quantum mechanics. Heisenberg recognized that if it were possible to measure the momentum and the position simultaneously with a greater accuracy, the quantum mechanics would collapse. So he proposed that it must be impossible.

Heisenberg’s uncertainty principle is a fundamental, inescapable property of the world.

They got this guy, in Germany. Fritz Something-or-other. Or is it? Maybe it's Werner. Anyway, he's got this theory, you wanna test something, you know, scientifically — how the planets go round the sun, what sunspots are made of, why the water comes out of the tap — well, you gotta look at it. But sometimes you look at it, your looking changes it. Ya can't know the reality of what happened, or what would've happened if you hadn't-a stuck in your own goddamn schnozz. So there is no "what happened"? Not in any sense that we can grasp, with our puny minds. Because our minds... our minds get in the way. Looking at something changes it. They call it the "Uncertainty Principle". Sure, it sounds screwy, but even Einstein says the guy's on to something.

The Principle of Uncertainty is a bad name. In science, or outside of it, we are not uncertain; our knowledge is merely confined, within a certain tolerance. We should call it the Principle of Tolerance. And I propose that name in two senses. First, in the engineering sense: Science has progressed, step by step, the most successful enterprise in the ascent of man, because it has understood that the exchange of information between man and nature, and man and man, can only take place with a certain tolerance. But second, I also use the word, passionately, about the real world. All knowledge – all information between human beings – can only be exchanged within a play of tolerance. And that is true whether the exchange is in science, or in literature, or in religion, or in politics, or in any form of thought that aspires to dogma. It's a major tragedy of my lifetime and yours that scientists were refining, to the most exquisite precision, the Principle of Tolerance – and turning their backs on the fact that all around them, tolerance was crashing to the ground beyond repair. The Principle of Uncertainty or, in my phrase, the Principle of Tolerance, fixed once for all the realization that all knowledge is limited. It is an irony of history that at the very time when this was being worked out, there should rise, under Hitler in Germany and other tyrants elsewhere, a counter-conception: a principle of monstrous certainty. When the future looks back on the 1930's, it will think of them as a crucial confrontation of culture as I have been expounding it – the ascent of man against the throwback to the despots' belief that they have absolute certainty.

Even if it were possible to cast my horoscope in this one life, and to make an accurate prediction about my future, it would not be possible to 'show' it to me because as soon as I saw it my future would change by definition. This is why Werner Heisenberg's adaptation of the Hays Office — the so-called principle of uncertainty whereby the act of measuring something has the effect of altering the measurement — is of such importance. In my case the difference is often made by publicity. For example, and to boast of one of my few virtues, I used to derive pleasure from giving my time to bright young people who showed promise as writers and who asked for my help. Then some profile of me quoted someone who disclosed that I liked to do this. Then it became something widely said of me, whereupon it became almost impossible for me to go on doing it, because I started to receive far more requests than I could respond to, let alone satisfy. Perception modifies reality: when I abandoned the smoking habit of more than three decades I was given a supposedly helpful pill called Wellbutrin. But as soon as I discovered that this was the brand name for an antidepressant, I tossed the bottle away. There may be successful methods for overcoming the blues but for me they cannot include a capsule that says: 'Fool yourself into happiness, while pretending not to do so.' I should actually want my mind to be strong enough to circumvent such a trick.

The utmost possible regarding an individual is a statement as to some order of probability about the future. Heisenberg's principle has been seized upon as a basis for wild statements to the effect that the doctrine of arbitrary free will and totally uncaused activity are now scientifically substantiated. Its actual force and significance is generalization of the idea that the individual is a temporal career whose future cannot logically be deduced from its past.

With Heisenberg's uncertainty principle, the fundamental role of experimental errors became a basic feature of physics.

Yet, the principle of uncertainty is a bad name. In science or outside of it, we are not uncertain. Our knowledge is merely confined within a certain tolerance. We should call it the principle of tolerance. First in the engineering sense. Science has progressed, step by step, the most successful enterprise in the ascent of man, because it has understood that the exchange of information between man and nature, and man and man, can only take place with a certain tolerance. But I also use the word, passionately, about the real world. All knowledge, all information, between human beings, can only be exchanged within a play of tolerance, and that's whether it's in science, or in literature, or in religion, or in politics, or in any form of though that aspires to dogma.

The uncertainty principle signaled an end to Laplace’s dream of a theory of science, a model of the universe that would be completely deterministic: one certainly cannot predict future events exactly if one cannot even measure the present state of the universe precisely! We could still imagine that there is a set of laws that determine events completely for some supernatural being, who could observe the present state of the universe without disturbing it.

The uncertainty principle signaled an end to Laplace's dream of a theory of science, a model of the universe that would be completely deterministic. We certainly cannot predict future events exactly if we cannot even measure the present state of the universe precisely!

We could still imagine that there is a set of laws that determine events completely for some supernatural being who, unlike us, could observe the present state of the universe without disturbing it. However, such models of the universe are not of much interest to us ordinary mortals. It seems better to employ the principle of economy known as Occam's razor and cut out all the features of the theory that cannot be observed.

If only we could get hold of a German atomic physicist, we felt, we could soon find out what the rest of them were up to. To us physicists the problem seemed very simple. Even those of us who were not working on the atom bomb project knew pretty well what was going on over here. No amount of military security could have prevented us from knowing, difficult as it was for the military to understand this. Active scientists engaged in the same general field of research inevitably form a kind of clan; they work closely together and know all about each other's specialities and whereabouts. You can't take a group of key scientists from their accustomed haunts and have them disappear in some remote place in New Mexico, together with their families, without their colleagues who are left behind wondering about it and deriving the right conclusions. The same thing, we knew, would be true of the Germans.

It is impossible to imagine a more dramatic and horrifying combination of scientific triumph with political and moral failure than has been shown to the world in the destruction of Hiroshima. From the scientific point of view, the atomic bomb embodies the results of a combination of genius and patience as remarkable as any in the history of mankind.

With both light and electrons, one was faced with the so-called "wave-particle duality"; both could be regarded as waves for some purposes and as particles for others. An important step in resolving this paradox was a paper by Max Born in July 1926, in which he suggested that the waves determine the probability of finding the particle in a particular place. This idea was already considered much earlier by Einstein, but it was rejected by him. This interpretation of the theory was further developed in the spring of 1927 by Heisenberg, who formulated his "uncertainty principle" ...

Classical science was based upon the belief that it is possible to formulate both the position and velocity at one time of any given particle. It followed that knowledge of the position and velocity of a given number of particles would enable the future behavior of the whole collection to be accurately predicted. The principle of Heisenberg is that given the determination of position, its velocity can be stated only as of a certain order of probability, while if its velocity is determined the correlative factor of position can be stated only as of a certain order of probability. Both cannot be determined at once, from which it follows necessarily that the future of the whole collection cannot possibly be foretold except in terms of some order of probability.