身近な科学
Why can't we predict when one nucleus will decay?
After three half-lives, an ideal radioactive population has one eighth of its initial undecayed nuclei remaining.
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短い答え
After three half-lives, an ideal radioactive population has one eighth of its initial undecayed nuclei remaining.
本当は何が起きている？
A half-life does not mean every nucleus survives exactly that long; it is a statistical property of a population.
役立つイメージ
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Radioactive decay is probabilistic for an individual nucleus. Half-life describes the statistical behaviour of a large population, not a countdown timer attached to each atom.