Aperiodical Maths News - <a href="https://www.scientificamerican.com/article/new-knot-theory-discovery-overturns-long-held-mathematical-assumption/">A knot's unknotting number is not additive under connected sum of knots</a> <br> <br> (via <a href="https://mathstodon.xyz/@Ianagol/115137713510052214">Ian Agol</a>)