Convert Femtometer (fm) to Ell (ell) instantly.
About these units
Femtometer (fm)
A femtometer, equal to 10⁻¹⁵ meters, is the scale at which the structure of atomic nuclei becomes measurable. Also known historically as a "fermi," this unit is used extensively in nuclear physics to describe the radii of protons, neutrons, and nuclei, which typically span 1–10 femtometers. At this scale, the strong nuclear force dominates interactions, and classical intuition breaks down almost entirely—quantum mechanics provides the only meaningful framework. The femtometer also plays a role in high-energy particle experiments, where the wavelengths of probing particles (like high-velocity electrons) may be expressed in femtometer increments. These small wavelengths allow researchers to resolve sub-nuclear structures. While invisible to any optical instrument, distances in the femtometer range can be inferred through scattering experiments, such as those performed in particle accelerators.
Ell (ell)
The ell is a traditional European unit of length, varying between 45–70 cm depending on the region. It originated from the forearm or arm length and became standardized in many countries for measuring cloth and textiles. In commerce, the ell simplified transactions, allowing merchants to describe fabric lengths efficiently. In tailoring, it offered a consistent basis for cutting and patterning clothing. The unit was essential in guild systems, where precision and repeatability in textile production were critical. While largely obsolete today due to the metric system, the ell remains significant for historians, textile scholars, and anyone studying pre-modern European commerce and craft practices.