New Scientist Default Image

Not every tangle is really a knot

Alex Walker/Getty Images

Unraveling knots just got easier. One of the biggest problems in the mathematical study of knots is recognising the difference between an actual knot and a piece of string that can be untangled into a single loop. A new algorithm can find this “unknot” far faster than any previous one, which could come in handy for studying the tangles of DNA or the fluid dynamics of stars.

Mathematically, the definition of a knot is a closed curve – like a piece of string with the ends tied together – …