6.1 Lindblad’s theorem
Although the fundamental laws of physics explain a great deal of the material world, they often seem to contradict our immediate experience. For instance, as physicists we believe that all elementary interactions are reversible, but as people we are immersed in irreversibility. The collision of two atoms may well be reversible and predictable, but for us time flows in a definite direction and life is sometimes unpredictable. “What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know.” (Attributed to Augustine.) Nevertheless, as we try to explain in this section, one can include irreversibility, the true arrow of time, into quantum mechanics ...