also an engineer. My analogy has been: "consider how hard it would be for a mosquito to pass through a cyclone fence?" That usually wakes them up. (However, it is probably a white lie by a factor of two!) 0.1 micron vs 0.5 micron holes or 0.2" vs 2" cyclone fence holes. Exaggeration can be useful to at least cause lucidity in the blind. Later, offer reality.