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  "body": "\n## Summary\n\nA problem is well posed in the sense of Hadamard if it has a unique solution that depends continuously on the data.\nThese conditions say that a model of a physical process gives one answer, stable under small errors in the data.\nA problem that fails one of them is ill posed; such problems, like the backward heat equation or many inverse problems, need extra care.\nSee the [[definition|FZ64956KX2]].\n\n## Explanations\n\n### L1 human\n\nData from the real world always carry small errors.\nIf a tiny change of the data could change the answer completely, the model would be useless for prediction.\nA well-posed problem has exactly one answer, and nearby data give nearby answers.\nFor example, fixing the temperature on the edge of a disc determines the steady temperature inside.\nChanging the edge values by at most $0.1$ degrees changes the inside by at most $0.1$ degrees.\n",
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