“In the future, maybe quantum mechanics will teach us something equally chilling about exactly how we exist from moment to moment of what we like to think of as time.” -Richard K. Morgan

It’s absolutely true that, in quantum mechanics, there are certain pairs of properties that we simply can’t measure simultaneously. Measure the position of an object really well, and its momentum becomes more uncertain. Measure its energy, and its time becomes more uncertain. And measure its voltage, and the free charge becomes more uncertain. Although this is disconcerting to some, it’s a fundamental part of the quantum nature of the Universe.

An illustration between the inherent uncertainty between position and momentum at the quantum level. Image credit: E. Siegel / Wikimedia Commons user Maschen.

But there’s also more to it than that! Not only are pairs inherently uncertain, but each component has some built-in uncertainty that you can never take away. Moreover, it arises from a simple fact that isn’t true classically: the order of operations — whether you measure position or momentum first — makes a fundamental difference in what you get out. This quantum commutation relation is where so much of the fundamental quantum weirdness in our Universe comes from.

A modern high field clinical MRI scanner. MRI machines are the largest medical or scientific use of helium today, and make use of quantum transitions in subatomic particles. Image credit: Wikimedia Commons user KasugaHuang.

It’s also why we have technologies like atomic clocks, hydrogen masers, and MRI machines! Come find out where quantum uncertainty arises from, and why it matters, on this week’s Ask Ethan!


  1. #1 Elle H.C.
    August 12, 2017

    Cool to see the QCD animation of how particle/antiparticle pairs pop up, how connected ‘holes’ show up and how the Vacuum starts to be shake up. Curious if these tremblings differ very much from Gravity waves?!

  2. #2 Steve
    August 12, 2017

    Uncertainty is a principle to live by

  3. #3 D. C. Sessions
    Central New Mexico
    August 12, 2017

    Voltage and charge have a different product from the others?

    This is news to me.