  We present a very simple model of a spontaneous emission from a two-level
atom, interacting with a field of a finite number of states. Such a process is
often said to occur because of the large number of equally-probable states of
environment. We show that in our model increasing the number of field states
may and may not cause a practically permanent emission, depending on the
details of the model. We also describe how irreversibility emerges with growing
number of states. Mathematical tools are reduced to a necessary minimum and
hopefully can be well understood by undergraduate students.
