Hot debate: When a horse gallops, is there ever a moment where all four hooves leave the ground? AD 1872 required new electric shutter technology: Muybridge and Stanford Muybridges multi-camera Muybridges galloping horse (1878) realistic crystal of horses average structure: galloping horse average structure: 1-sigma contour Muybridges galloping horse (1878) Real spacereciprocal Time-resolved diffraction Muybridges galloping horse (1878) Real spacereciprocal Average intensity Muybridges galloping horse (1878) Real spacereciprocal Average electron density Muybridges galloping horse (1878) Real spacereciprocal Sum(intensity) Sum(density) = diffuse scatter Muybridges galloping horse (1878) Real spacereciprocal F incoh F coherent with density phases Muybridges galloping horse (1878) Real spacereciprocal RMS variation in density Supporting a model with data