In different books, but also websites, there are different expressions for the Heisenberg's uncertainty principle. For example,

  • $\Delta x \Delta p \ge h$ (from The Physics of Atoms and Quanta)
  • $\Delta x \Delta p \ge \hbar/2$ or
  • $\Delta x \Delta p \ge \hbar$ (Demtroder)


Which one of these notations is the correct one? Or, if they're all correct, could someone provide me with some examples or context where each of them is used?

  • $\begingroup$ of course if something is largher than h_bar it is also larger than h_bar/2 $\endgroup$ – anna v Nov 24 '18 at 14:04
  • 2
    $\begingroup$ @anna v. Making this question a duplicate is an example of the situation I am blaming in my answer to the meta post <a href="physics.meta.stackexchange.com/questions/10898/… the demise of Stack Exchange (as we know it) ineluctable? </a>. I think that all the answers to the previous question have missed an important point. However, replying to a question of more than 2 yeas ago, will hardly be noticed, staring with the person who has asked the present question. $\endgroup$ – GiorgioP Nov 24 '18 at 14:27
  • 1
    $\begingroup$ @GiorgioP According to you, which is the point that all the answers to this question have missed? $\endgroup$ – physicist Nov 24 '18 at 14:47
  • 2
    $\begingroup$ @GiorgioP I disagree. If the answers there have missed the point, people are invited to go to the other thread and answer: we will end up with all the good answers collected in one place. That is much better than the case where the good answers are spread across a bunch of different places. $\endgroup$ – user191954 Nov 24 '18 at 15:01
  • 1
    $\begingroup$ @Chair: the spreading in a bunch of places is a technological limit of the platform. From the logical point of view, it would be enough to consider answers to the most recent question as continuation of the answers to the old one. I am used to think that logical needs should prevail on technological limits of the message organization. But this is matter for meta forum, I guess. $\endgroup$ – GiorgioP Nov 24 '18 at 15:31