Eur. Phys. J. Plus (2012) 127: 11
https://doi.org/10.1140/epjp/i2012-12011-5

Regular Article

The physical basis of natural units and truly fundamental constants

¹ Department of Postsecondary Teaching and Learning, University of Minnesota, 55455, Minneapolis, MN, USA
² Department of Physics, University of Massachusetts-Dartmouth, 02747, North Dartmouth, MA, USA

^* e-mail: lhsu@umn.edu

Received: 25 July 2011
Accepted: 7 December 2011
Published online: 27 January 2012

Abstract

The natural unit system, in which the value of fundamental constants such as c and ℏ are set equal to one and all quantities are expressed in terms of a single unit, is usually introduced as a calculational convenience. However, we demonstrate that this system of natural units has a physical justification as well. We discuss and review the natural units, including definitions for each of the seven base units in the International System of Units (SI) in terms of a single unit. We also review the fundamental constants, which can be classified as units-dependent or units-independent. Units-independent constants, whose values are not determined by human conventions of units, may be interpreted as inherent constants of nature.