  Karl Popper had proposed an experiment to test the standard interpretation of
quantum mechanics. The proposal survived for many year in the midst of no clear
consensus on what results it would yield. The experiment was realized by Kim
and Shih in 1999, and the apparently surprising result led to lot of debate. We
review Popper's proposal and its realization in the light of current era when
entanglement has been well studied, both theoretically and experimentally. We
show that the "ghost-diffraction" experiment, carried out in a different
context, conclusively resolves the controversy surrounding Popper's experiment.
