Two mathematicians have proved that a straightforward question — how hard is it to untie a knot? — has a complicated answer.

Graphene's journey from discovery to industrial use has been marked by impressive progress. It was first discovered in 2004, ...

So practically no teenagers have kids (a good thing). Very few women in their early 20s having kids (probably also a good thing). Age of marriage and family formation rising (also a good thing for ...