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  "body": "\n## Summary\n\nThe unknotting number of a [[knot|QYEAZTYGPT]] is the least number of crossing changes needed to turn it into the [[unknot|1TQ06R4Q66]].\nIt is a [[knot invariant|GZQ5ZE3X6G]] that measures how far a knot is from being trivial.\nIt is easy to define but often hard to compute, and it is still unknown for some knots with only ten crossings.\n\n## Explanations\n\n### L1 human\n\nThink of a knot as a tangled loop of rope, drawn on paper with over- and under-crossings.\nA crossing change lets one strand pass through the other at one crossing, so the over-strand becomes the under-strand.\nThe unknotting number counts how many such passes are needed, at best, to get a plain loop.\nYou may move the rope around freely between the passes.\nThe [[trefoil knot|VYTYSVHN4A]] has unknotting number $1$: one crossing change in its usual picture undoes it.\n",
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