The irreversibility of time

Delta prime said:

Heisenberg’s uncertainty principle, which is often presented as a statement about the intrinsic uncertainty that a quantum system must possess. Yet Heisenberg originally formulated his principle in terms of the “observer effect”: a relationship between the precision of a measurement and the disturbance it creates, as when a photon measures an electron’s position.

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The uncertainty principle is a mathematical statement, and Heisenberg originally formulated it by working through the math. The "observer effect" analogy came later in a pop sci article (or essay, I don't remember), where Heisenberg used it to explain uncertainty to laymen. Needless to say, he used a terrible analogy, as the observer effect (a classical notion) has been firmly ingrained in popular thought.