Two mathematicians have proved that a straightforward question—how hard is it to untie a knot?—has a complicated answer.
Photos and letters show how James Watson and Francis Crick raced to uncover the double helix structure of DNA.
James Watson, who co-discovered the structure of DNA has died at age 97. He was a scientific superstar until he made racist remarks that made him an outcast.
Some results have been hidden because they may be inaccessible to you
Show inaccessible results
Feedback