  Late in October 1911, eighteen leading scientists from all over Europe met to
the first of a famous sequence of Solvay conferences in Brussels. This
historical meeting was mainly devoted to "The Theory of Radiation and the
Quanta", at a time when the foundations of physics were totally shaken.
Although "nothing positive came out" (Einstein), it is interesting to see the
diverging attitudes of Europe's most famous scientists in the middle of the
quantum revolution. After a few general remarks about the conference, I shall
focus on some of the most interesting contributions and discussions. Einstein,
at 32 the youngest, was clearly most aware of the profound nature of the
crises. He gave the final talk entitled "The Present State of the Problem of
Specific Heats", but he put his theme into the larger context of the quantum
problem, and caused a barrage of challenges, in particular from Lorentz,
Planck, Poincar\'{e}, and others.
