[2] After Harvard, Vishniac spent two years as a post doctoral fellow working under Jeremiah P. Ostriker at Princeton University.
His best known scientific work is the study of instabilities in expanding blast waves.
In Vishniac (1983), he demonstrated that a blast wave expanding in a sufficiently compressible medium would be subject to a linear overstability growing as the square root of time.
This is usually known as the Vishniac instability, and generally occurs in any thin enough slab bounded by a shock on one side and a contact discontinuity to a higher temperature region on the other.
His wife Ilene Busch-Vishniac, the ninth president of the University of Saskatchewan (2012–2014), was previously Dean of the Faculty of Engineering at Johns Hopkins, and provost and vice-president (academic) of McMaster University from 2007 until 2012.