Bachelors' unknotting is a way to show that all tame knots are isotopic to the unknot, by tightening a knot to a point. Why is it called 'bachelors' unknotting'?

  • $\begingroup$ Note that it is "bachelors' unknotting". The earliest instance I have been able to locate at this time, which provides no explanation of the name, is: Peter R. Cromwell, Knots and Links, Cambridge University Press 2004, p. 4: " Because mathematical thread has no thickness, we can reduce a mathematical know until it becomes a point and disappears. This continuous transformation, known as bachelors' unknotting, is sketched in Figure 1.4 " $\endgroup$
    – njuffa
    Dec 5, 2022 at 21:29
  • $\begingroup$ Given that 2004 does not qualify as history in my thinking, I was going to suggest contacting Dr. Cromwell by email, but found that his staff web page at the University of Liverpool is empty. $\endgroup$
    – njuffa
    Dec 5, 2022 at 21:47
  • $\begingroup$ @njuffa I actually learnt about this term from Cromwell's book. I'll see if I find any older source. I initially thought the term might be related to some western cultural norm or custom regarding weddings. Apologies for replying late. $\endgroup$ Dec 17, 2022 at 6:07
  • $\begingroup$ Possible an instance of British humor? People who get married are said to "tie the knot". If one does that in reverse (unknotting), the groom will then turn back into a bachelor. Just a wild hypothesis. $\endgroup$
    – njuffa
    Dec 17, 2022 at 6:49
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    $\begingroup$ @njuffa I found a reference from 2001, earlier than Cromwell: liverpool.ac.uk/~su14/papers/KNOT2002.pdf. It reads "The one manoeuvre which must be excluded is the analogue of the bachelor’s technique for ignoring knots on a piece of cotton – pull it so tight that you can hardly see it! Using this technique on a curve with no physical thickness would get rid of any knot." on pages 3--4. $\endgroup$ Mar 20, 2023 at 14:10


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