  We estimate the changes in the condensate ground state energy induced by one
or more "sizable" impurities. By "sizable", we mean an impurity whose size is
within a few orders of magnitude of the trap size and not necessarily atomic in
scale. A sizable impurity will "drill" a hole in the condensate wave function
and alter the condensate energy. The question is whether this microscopic
change can be detected macroscopically because of the Bose-Einstein
condensation effect. We discuss the effect of impurity expulsion, condensate
interactions, and the induced interaction between two impurities.
