N(t) = N₀ · 2^(−t/T½)
☢️ Decay & Dating
Pick an isotope (C-14, I-131, U-238… or your own half-life) and compute what fraction survives after any time — or flip it around: enter the remaining percentage and get the sample's age, carbon-dating style, with the decay curve drawn live as you drag.
Decay curve — drag the marker
After each half-life exactly half of what's left decays: 1 → ½ → ¼ → ⅛… Carbon dating works to ~50,000 years (beyond ~9 half-lives too little C-14 remains to measure). Half-life values are physical constants; activity (Bq) falls by the same 2^(−t/T½) factor as the atom count.