How to use it
Drag Position spread Δx. The top curve (where the particle is) narrows — and the bottom curve (its momentum) widens, automatically. The meter shows the product Δx·Δp, which can never drop below ℏ/2. Switch the state to see shapes that sit above the floor.
What you're actually seeing
Two views of one quantum state. Top: |ψ(x)|², the probability of position. Bottom: |φ(p)|², the probability of momentum — the Fourier transform of the top. They are the same object in two languages; you cannot make both narrow at once.
It's not about disturbance
The popular story — "measuring kicks the particle" — is Heisenberg's 1927 heuristic, not the principle. The real statement (Kennard 1927) is about preparation: no wave can have both a sharp position and a sharp momentum, because narrow-in-x means broad-in-p. It's a theorem about Fourier transforms, true before anyone looks.
What's exact, what's stylised
Exact: the bound Δx·Δp ≥ ℏ/2, the Gaussian saturating it, the Fourier relationship, and the real electron numbers. Stylised: the carrier-wave animation and scaled display units; Δx is read as nanometres for the real-scale figure.