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

Rock and roll is alive and well atop the Billboard 200 albums chart this week, as Twenty One Pilots' Breach hits No. 1.

Specialists caution that there isn’t a universal portrait that captures the state of higher education around the world.

President Donald Trump’s approval rating declined one point in a Reuters/Ipsos poll released Tuesday—hours after Trump claimed he has the “highest poll numbers [he’s] ever had”—keeping his rating ...