Attometer
An attometer (am) is a unit of length in the metric system, equal to one-quintillionth of a meter (1 am = 10⁻¹⁸ meters). This unit is extremely small, even smaller than a femtometer, and is used in theoretical physics to describe distances at the quantum level, such as within particles or in advanced models of spacetime. However, attometers are rarely used in practice because most known physical structures, including subatomic particles, are still larger than this. The attometer mainly appears in scientific equations or hypotheses dealing with concepts beyond current experimental capabilities.
Barleycorn
A barleycorn is an old English unit of length, traditionally based on the length of a grain of barley. It is defined as exactly 1/3 of an inch or approximately 8.47 millimeters.
Historically, the barleycorn was used for measuring small lengths and was also the basis for the inch, which was originally considered to be three barleycorns long. It played a role in various traditional measurements, including shoe sizing in English-speaking countries, where shoe sizes were sometimes expressed in barleycorn units.
Although obsolete as a formal unit, the barleycorn remains culturally significant, especially in shoe sizing systems.
Summary:
1 barleycorn = 1/3 inch ≈ 8.47 mm
Based on the length of a grain of barley
Used historically in small measurements and shoe sizing
Mostly of historical and cultural interest today
No conversions available for length.