Ken Wilson died last saturday. He was arguably one of the most important theoretical physicists of the second half of the twentieth century. He pioneered the marriage of quantum field theory techniques with condensed matter. He developed key concepts and methods including scaling, universality, the renormalisation group, epsilon=4-d expansions, numerical solution of the Kondo problem, and lattice gauge theory.
I first heard of Wilson as a first year undergraduate when I read his 1979 Scientific American article, Problems in physics with many scales of length. I had no idea what it was all about. When I was a postdoc at Ohio State he had an office near mine. Then he was mostly interested in science education reform.
There are obituaries at Ohio State and Cornell.
A previous post considers Wilson's comments about quantum chemistry, in a long and meandering interview about his career.