12 At the history-making Solvay conference in Brussels of 1927, de Broglie, supported by Einstein, proposed the pilot wave theory. However, at the same conference, Heisenberg and Max Born introduced their theory of quantum mechanics, a theory of particles that explains discrete or “quantal” properties observed on the quantal scale. Their theory was embraced, though Einstein complained that it did not fully explain the physical world, and became the hegemonic position in theoretical physics.