Vis mortua

From Hmolpedia
Jump to navigation Jump to search
A screenshot of Portuguese weightlifter demonstrating how to do a correct "dead lift", aka "corrigir o peso porto!" in Portuguese.[1] Galileo's use of the term "peso morto" (1638), in reference to heavy bodies, eventually became a terminology prototype for Leibniz's "vis mortua" or dead force, a term eventually replaced by "potential energy" (Rankine, 1853).

In terms, vis mortua (CR:5) (LH:10) (TL:15), from "vis", meaning: "force" (of Venus), + Mor-, meaning: Roman death god, translates either as "dead force", or dead weight, depending on context; the term, now classified as defunct and obsolete, was eventually replaced with "potential energy" (Rankine, 1853).


In 1638, Galileo was using the Latin term "peso morto"[2], meaning "dead weight". In modern Portuguese, the term "peso morto" translates into the modern English as the exercise term "dead lift", referring to the power lifting exercise wherein a person lifts an olympic bar, loaded with two or more 45-lbs plates, off the ground.

Galileo, presumably, was doing some sort of experiments, in an attempt to quantify how much "work", using modern terminology, was required to either raise a weight and or to drop various weights in free fall.

Etymologically, vis and mortua derive from the Roman "life god" (Venus) and "death god" (Mor), respectively:

  • Vis = force of Venus
  • Morto = dead[3]; life (or body) carried off by Mor

This so-called "mythical terminology", employed to describe and quantify physics experiments, while it functioned for about two centuries, eventually began to become objectionable terminology, in the mid 19th century. Originally, these Latin terms were employed by Gottfried Leibniz, among others, and carried used in Latin and in French scientific discussion for two centuries, until it was finally replaced, in English science discourse, by William Rankine (1853) with the term "potential energy".

The following summarizes the history of how vis viva and vis mortua became scientifically neutral terms:

Original Intermediate Reformation
Momento | Quasi force
(Galileo, 1592)

(Descartes, 1640)

(Huygens, 1669)
Vis viva | Living force
(Leibniz, 1686)
T or
(Lagrange, 1788)
Actual energy
(Rankine, 1853)
Kinetic energy
(Thomson, 1862)
(Clausius, 1875)
Peso Morto | Dead weight
(Galileo, 1638)
Vis mortua | Dead force
(Leibniz, 1673)
(Lagrange, 1788)
Latent energy Potential energy
(Rankine, 1853)
J or ergal
(Clausius, 1875)

In sum, in the 17th century, Latin language, the scientific standard, was employed by Galileo, e.g. "peso morto" (dead weight), and Leibniz, e.g. vis viva (living force) and vis mortua (dead force), to describe motions and energies associated with metal balls being dropped, collided together, or being in a position of height.


The following are quotes:

Vis mortua and vis viva, in mechanics, are terms used by Leibnitz and his followers for ‘force’, which they distinguish into two kinds, vis mortua, and vis viva; understanding by the former any kind of ‘pressure’, or an endeavor to move, not sufficient to produce actual motion, unless its action on a body be continued for some time; and by the latter, that force or power of acting which resides in a body in motion.”
— Charles Hutton (1815), A Philosophical and Mathematical Dictionary, Volume Two (pg. 568)[4]
“It is difficult to trace the origin of the viva-mortua distinction in the dynamics because, although the term vis mortua was used as early as 1673 in correspondence with Mariotte and then 1675 in De arcanis motis, it did not receive systematic treatment until much later in the 1689 Phoranomous and other texts of the period. The term is also conspicuously absent from many of the intermediate milestone texts toward the constitution of the dynamics project in 1689, like De corporum concursu and the highly public Brevis demonstratio. Nonetheless, the obvious forebear of the viva-mortua distinction is Galileo's circa 1600 Della scienza mecanica: e delle vtilita che si traggono dagl'instromenti di quella (translated by Mersenne in 1634) where he defines the term ‘momenta’ [moment] as the ‘impetus to go downward, composed of heaviness, position and of anything else by which this tendency may be caused’ (Galilei 1960, 151). More to the point, in the uncompleted ‘sixth day’ of Galileo's Discorsi e Dimostrazioni, he distinguishes between the force of a moving body and that of a ‘dead weight’ (peso morto) (Galilei 1898, 334-335, 1974, 294-295). Certainly, the phenomenon identified by Galileo was the same as that which was identified by Leibniz even where ‘peso morto’ has become ‘vis mortua’. However, without the more systematic dynamical articulation, it is difficult to ascribe this distinction with any rigor to Leibniz before the mature development of the dynamics.”
— Tzuchien Tho (2017), Vis Vim Vi: Declinations of Force in Leibniz’ Dynamics (pg. 80)[5]

End matter


  1. Salgueiro, Dicas. (2015). “Corrigir o Peso Morot!” (Correct Dead Lift!) (YT), Dicas do Salgueiro, Nov 1.
  2. peso morto – Wiktionary.
  3. morto – Wiktionary.
  4. Hutton, Charles. (1815). A Philosophical and Mathematical Dictionary, Volume Two (pg. 568). Publisher.
  5. Tho, Tzuchien. (2017). Vis Vim Vi: Declinations of Force in Leibniz’ Dynamics (pg. 80). Springer.

External links

Theta Delta ics T2.jpg