Protective helmet

A protective helmet. The protective helmet includes an outer layer and an inner layer, each formed of a hard material. The outer layer and the inner layer each further include a concave interior surface and a convex exterior surface. A flexible connector connects the concave interior surface of the outer layer to the convex exterior surface of the inner layer. The flexible connector is configured to allow the outer layer to laterally shift relative to the inner layer upon impact to the protective helmet. Upon impact, the convex surface moves along the inclined planed of the concave surface in a direction opposite of the impact, while the stretched flexible connector provides a restoring force pulling the inner and outer layers back to their original positions.