Convert Span (Cloth) (span) to Planck Length (ℓₚ) instantly.
About these units
Span (Cloth) (span)
The span is a unit traditionally used in textile measurement, equal to the distance between the tip of the thumb and the tip of the little finger when the hand is fully extended, approximately 22.86 cm (9 inches). This anthropometric unit was widely used by weavers and cloth merchants to measure lengths of fabric quickly and intuitively. Its small scale made it convenient for practical applications where tape measures or rulers were unavailable. The span also appears in cultural and historical texts as a natural unit of human proportion. While largely obsolete today, it offers insight into pre-industrial textile practices and the anthropometric basis of early measurement systems.
Planck Length (ℓₚ)
The Planck length, approximately 1.616 × 10⁻³⁵ meters, is perhaps the most conceptually profound unit in physics. It represents the scale at which classical notions of space and time cease to exist and quantum gravity effects dominate. Below this length, it is believed that spacetime becomes "foamy," subject to fluctuations predicted by quantum field theory and speculative models such as string theory. The Planck length is derived from fundamental constants: the speed of light, Planck's constant, and Newton's gravitational constant. These constants combine to yield a natural scale where both quantum mechanics and general relativity must merge into a unified theory. No experiment has ever probed distances anywhere near the Planck scale — it is many orders of magnitude smaller than even the size of protons — but it plays a crucial role in theoretical cosmology, black hole physics, and models of the early universe. The Planck length stands as a symbol of the limits of physical measurement and the frontier of fundamental physics.