[l33tman]

This is not a correct description at all of QM complementary observables. This is a purely classical explanation (and was one of the first layman "explanations" back in 1920, but that was 100 years ago and QM is much better understood now).

[mercer]

Could you elaborate on that? From my extremely limited knowledge it does seem like a just-so explanation (what you're responding to), but I'm not sure why.

[chriswarbo]

The 'measuring something disturbs it' idea described above is called the observer effect https://en.wikipedia.org/wiki/Observer_effect_(physics)

The observer effect is a real thing, and even has interesting effects in quantum mechanics, e.g. the quantum zeno effect https://en.wikipedia.org/wiki/Quantum_Zeno_effect

Yet the observer effect is not the reason why we can't know an object's position and velocity at the same time. There are two ways we can see that this supposed explanation is a red herring:

- We don't need to interact with (e.g. 'bounce a photon off') a quantum system in order to observe it ( https://en.wikipedia.org/wiki/Interaction-free_measurement ). I particularly like the "quantum bomb detector" ( https://en.wikipedia.org/wiki/Elitzur%E2%80%93Vaidman_bomb_t... ), which can tells us whether a photon detector connected to a bomb is working or not, without hitting it with a photon and hence triggering the bomb (50% of the time, at least).

- The actual reason, the uncertainty principle ( https://en.wikipedia.org/wiki/Uncertainty_principle ), doesn't require any notion of observation at all, let alone interaction. It's a simple property of waves (the relationship between duration and frequency). 3blue1brown did a nice video on this https://www.youtube.com/watch?v=MBnnXbOM5S4