Convert Handbreadth (handbreadth) to Bohr Radius (a₀) instantly.
About these units
Handbreadth (handbreadth)
The handbreadth, roughly 0.1 meter, represents the width of a human hand with fingers extended. It served as a convenient, body-based subunit for cubits and larger measures. Handbreadths were integral to construction, tailoring, and craftwork, allowing precise division of larger units into manageable increments. In ancient Egyptian, Greek, and Hebrew measurement systems, the handbreadth facilitated scaling and proportioning for artisans and builders. Today, the handbreadth is mainly of historical interest, helping reconstruct ancient architectural plans and understand the human-centered logic of early measurement systems.
Bohr Radius (a₀)
The Bohr radius, equal to approximately 5.29177 × 10⁻¹¹ meters, is the most probable distance between the electron and nucleus in the ground state of hydrogen according to the Bohr model. While modern quantum mechanics has evolved far beyond the Bohr model, the radius remains a remarkably accurate approximation for average atomic dimensions. The Bohr radius acts as a natural "yardstick" for the size of atoms and is frequently used in atomic physics and quantum chemistry. Many atomic properties — orbital sizes, electron probability distributions, and energy levels — are conveniently expressed in multiples of the Bohr radius. Because it reflects fundamental constants, including Planck's constant and the electron charge, the Bohr radius also appears in theoretical analyses of physical systems and helps unify atomic physics concepts across different contexts.