Fermy

Fermy is a colloquial term, often used in informal scientific discussions, to refer to a unit of length equal to 10⁻¹⁵ meters. This unit is commonly known as a femtometer. The name "fermy" is a direct tribute to the Italian-American physicist Enrico Fermi, who made significant contributions to nuclear physics and particle physics. The femtometer is an extremely small unit, relevant in the realm of subatomic particles. For instance, the radius of a proton is approximately 0.8 femtometers, and the radius of a neutron is similarly around 0.8 femtometers. The size of atomic nuclei is also typically measured in femtometers. While the term "fermy" is not an official SI unit, it is widely understood and used by physicists when discussing the dimensions of elementary particles and atomic nuclei in contexts where precise scientific nomenclature might be slightly relaxed, such as in lectures or casual conversations among colleagues. The official SI prefix for 10⁻¹⁵ is "femto," making the femtometer the standard and formally recognized term.