**Heisenberg's uncertainty principle** or just the **uncertainty principle** is a principle in quantum physics which states that there is a limit to how precisely we can measure a particle's position and momentum at a given time. Mathematically, it is stated as

- $ \Delta x \Delta p \geq \frac{\hbar}{2} ~~ $

where *ħ* is the reduced Planck constant (or the Planck constant over 2π).