Convert Electron radius (classical) to span (cloth) Online | Free Length Converter

Classical Electron Radius

The classical electron radius is a theoretical length scale associated with the electron, derived from classical electromagnetism. It represents the size of a hypothetical sphere where the electron’s electrostatic energy equals its rest mass energy.

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  Its value is approximately 2.818 × 10⁻¹⁵ meters (about 2.8 femtometers).

  
  
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  Calculated using fundamental constants: the electron charge, mass, and the speed of light.

  
  
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  It is not the actual physical size of the electron (which is considered point-like in quantum mechanics), but a useful scale in classical physics.

  
  
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  Used in scattering theory and classical electron models.

  
  

Key facts:

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  Classical electron radius ≈ 2.818 × 10⁻¹⁵ m

  
  
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  Represents an electromagnetic length scale, not a physical size

  
  
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  Important in classical models of electron behavior

  
  

This radius helps bridge classical and quantum views of particle physics.

Span (Cloth)

A span is an old unit of length based on the distance between the tip of the thumb and the tip of the little finger of a fully extended hand. Traditionally, it measures about 9 inches or 22.86 centimeters.

In the context of cloth and textiles, the span was used as a convenient, informal measure to estimate small lengths of fabric before standardized rulers became widespread. It was helpful for tailors and traders to quickly gauge lengths during measuring and cutting.

While the span is largely obsolete as a formal unit today, it reflects historical measurement practices tied closely to the human body, similar to the cubit or hand.

Summary:

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  1 span ≈ 9 inches (22.86 cm)

  
  
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  Based on the hand’s spread

  
  
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  Used historically in cloth measurement and tailoring

  
  
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  Now mostly of historical and cultural interest