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  "body": "\n## Summary\n\nThe bridge number of a [[knot|QYEAZTYGPT]] is the least number of local maxima of the height on the knot.\nThe least is taken over all positions of the knot in space.\nIt is a [[knot invariant|GZQ5ZE3X6G]] introduced by Horst Schubert.\nKnots with bridge number $2$, the two-bridge knots, form a well-understood family that is classified completely.\n\n## Explanations\n\n### L1 human\n\nLay a knotted rope in space and look at its height above the floor.\nThe rope goes up and down; count the hilltops.\nThe bridge number is the smallest number of hilltops you can get by moving the rope around without cutting it.\nA plain circle has one hilltop, and nothing smaller is possible.\nThe [[trefoil knot|VYTYSVHN4A]] needs two hilltops, so its bridge number is $2$.\n",
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