Science Quote by Walter Kohn

There is a quiet audacity in that word “reasonably.” Kohn isn’t selling a revolution with fireworks; he’s doing something more subversive in scientific culture: shrinking a supposedly settled number and letting the consequences detonate on their own. In condensed-matter physics, a “threshold” is never just a threshold. It’s a permission slip for an entire community’s assumptions about how solids behave under stress, irradiation, heat, and time. By claiming the energy required to permanently kick a nucleus out of its lattice site is “substantially smaller” than believed, Kohn is effectively saying: your models have been comforting you.

The intent is technical, but the subtext is methodological. This is the scientist as correction mechanism, shaving error bars off a foundational parameter that governs radiation damage, defect formation, and the long-term reliability of materials. A lower displacement energy means defects form more easily than engineers expected; it implies more fragility in the crystalline order we like to treat as robust. That’s a cultural blow to any field that leans on “ideal solids” as a default mental picture.

Context matters: Kohn’s career helped legitimize treating the messy collective behavior of electrons and nuclei with rigorous, predictive frameworks. The quote fits that temperament. It’s not grandstanding; it’s a recalibration. The real rhetorical move is the contrast between “established” and “previously presumed.” He’s drawing a line between measurement (or principled calculation) and inherited belief, reminding the reader that physics advances less by genius moments than by disciplined, embarrassing updates to what everyone thought they already knew.