We consider the methods which can be used to filter, and we make estimates of the efficiency of the various filter schemes.

At this point it is worth recalling some of the early history of the Mössbauer effect. I got into the Mössbauer business in 1958 while spending a year at the University of Illinois at Urbana directing Hans Frauenfelder's group doing parity non-conservation experiments in beta decay while Hans was on sabbatical at CERN.

The Workshop on New Directions on Mössbauer Spectoscopy was organized to fill a need which I and a number of people to whom I spoke felt was no longer being met by the biennieal international conference on Applications of the Mössbauer Effect.

During his active scientific career, Stanley Ruby always addressed most fundamental aspects of physics without being a "reductionist" - asking questions regarding the fundamental interaction of electromagnetic waves with matter - nucleons, atoms, molecules and the condensed matter, and answering these questions with unique demonstration experiments. This recollection paper is intended to be a brief compilation of Stanley Ruby's selected contributions. They are creation and annihilation of acoustic phonons, chopped gamma-rays, and jump diffusion in condensed matter. In addition, Ruby's nuclear physics background fitted best for him to identify many new candidate nuclear resonant transitions across the nuclear periodic table; and his grasp of chemical physics led to the development of isomer shift systematic among isoelectronic compounds of 5s-5p atoms. Finally, Ruby's most pragmatic suggestion in 1974 to use synchrotron radiation to observe nuclear resonance, and its eventual demonstration, addressed many fundamental aspects of collective nuclear excitation process and gamma-ray coherence. Furthermore it opened many new avenues of application of the tool to a broader area of science which otherwise would have been impossible with the traditional approach of using radioactive sources in performing Mossbauer spectroscopy measurements.