How to use it
Press Stream. A source fires entangled pairs — one to Alice (left), one to Bob (right). Each detector gives a random ±1, but the pair is correlated. The graph plots that correlation vs the angle φ between the analyzers; the gauge shows the CHSH number |S|. Flip to the local hidden-variable universe and watch it fail to keep up.
What you're actually seeing
Bottom graph: measured correlation E = ⟨A·B⟩ (gold dots) against the quantum prediction −cos θ (cyan) and one local-realist model (tan line). The cyan curve bows outside the line — that gap is the violation. The gauge reads S = 3·E(φ) − E(3φ); quantum reaches 2√2 ≈ 2.83, no local theory beats 2.
EPR, Bell & the loopholes
Einstein (1935) argued the correlations meant hidden variables — a deeper, local reality. Bell (1964) proved any such theory obeys |S| ≤ 2, turning it into an experiment. Real tests (Aspect 1982; loophole-free 2015) measure S ≈ 2.4 — above 2. The remaining logical escape, superdeterminism, denies free choice of settings and can't be fully closed.
What's exact, what's stylised
Exact: the −cos θ correlation, the |S| ≤ 2 theorem, the 2√2 quantum bound, and the 50/50 marginals (you can't signal with it). Stylised: outcomes are sampled from the Born-rule distribution (not a collapse simulation); the local model shown is one representative; rates and the noise slider are for watchability.