Mach's principle
From Freepedia
Mach's principle is a hypothesis first stated by the physicist and philosopher Ernst Mach in 1893, which states that:
"The inertia of any system is the result of the interaction of that system and the rest of the universe. In other words, every particle in the universe ultimately has an effect on every other particle."
According to Mach's principle, which is an example of a relational theory, a single object (for example, the Earth) in an otherwise empty Universe would feel no inertial forces. It would be impossible to determine whether that object is rotating or not. According to Mach, the inertial forces on that object are caused by the sum of the gravitational forces from cosmic bodies such as the distant stars1; the rotation of that object only makes sense relative to these other objects. For an example of the inertial forces on that object, see Coriolis force.
In this sense, Mach's principle can be said to be a form of philosophical holism.
The above version of the principle is largely due to Albert Einstein, who brought the principle into mainstream physics whilst working on general relativity. Indeed it was Einstein who first coined the phrase Mach's principle. There is much debate as to whether Mach really intended to suggest a new physical law since he never states it explicitly. He is more concerned with criticising Newton's mechanics, in particular the idea of absolute space.
Mach's principle was never developed into a quantitative physical theory that would explain a mechanism by which the stars can have such an effect.1 Although Einstein was intrigued by Mach's principle, his general relativity does not fully agree with it. There have been attempts to formulate a theory which is more fully Machian, such as Brans-Dicke theory, but none have been completely successful.
Note
- Note 1: Max Born, Einstein's Theory of Relativity. Dover 1962, a translation of Born's 1924 book in German, which explained Relativity in non-mathematical terms.
See also
- Democratic principle (one possible "Mach principle")
- Equivalence principle
- Newtonian physics
- General relativity
- Inertial frame
- Absolute space
- Newton's bucket
- Frame-dragging
- Infinite space
References
- Bondi, Hermann; and Samuel, Joseph. The Lense--Thirring Effect and Mach's Principle. arXiv eprint server. Accessed on July 4, 1996. An important review explaining the multiplicity of "Mach principles" which have been invoked in the research literature (and elsewhere).
- {{{Author|}}}{{|{{{3}}}}}}|show1| (1995)}}{{{{{Year|}}}}}}|show1|.}} {{|{{{3}}}}}}|show1|[{{{URL}}}}} Mach's principle: from Newton's bucket to quantum gravity{{|{{{3}}}}}}|show1|]}}{{|{{{3}}}}}}|show1|, {{{Pages}}}}}{{|{{{3}}}}}}|Show1|, Boston: Birkhauser}}. {{{ID|}}} (Einstein studies, vol. 6)
- {{{Author|}}}{{|{{{3}}}}}}|show1| (1995)}}{{{{{Year|}}}}}}|show1|.}} {{|{{{3}}}}}}|show1|[{{{URL}}}}} Gravitation and Inertia{{|{{{3}}}}}}|show1|]}}{{|{{{3}}}}}}|show1|, {{{Pages}}}}}{{|{{{3}}}}}}|Show1|, Princeton: Princeton University Press}}. {{{ID|}}} This book advocates a somewhat plausible "Mach principle" which unfortunately resists a covariant statement, leading to somewhat confused writing in places, but this book is valuable nonetheless.
- {{{Author|}}}{{|{{{3}}}}}}|show1| (1973)}}{{{{{Year|}}}}}}|show1|.}} {{|{{{3}}}}}}|show1|[{{{URL}}}}} Gravitation{{|{{{3}}}}}}|show1|]}}{{|{{{3}}}}}}|show1|, {{{Pages}}}}}{{|{{{3}}}}}}|Show1|, San Francisco: W. H. Freeman}}. {{{ID|}}} This classic textbook discusses Mach's principle in section 21.12. See also the facsimile of Einstein's 1913 letter to Mach in Fig. 21.5, in which he mentions his expectation that in his forthcoming theory of gravitation, inside a rotating thin spherical shell, the spin axis of a gryoscope should be "dragged" as if by a Coriolis pseudoforce, an effect which was later confirmed theoretically by Lense and Thirring, and is currently being tested by Gravity Probe B.
- {{{Author|}}}{{|{{{3}}}}}}|show1| (1971)}}{{{{{Year|}}}}}}|show1|.}} {{|{{{3}}}}}}|show1|[{{{URL}}}}} Modern Cosmology{{|{{{3}}}}}}|show1|]}}{{|{{{3}}}}}}|show1|, {{{Pages}}}}}{{|{{{3}}}}}}|Show1|, Cambridge: Cambridge University Press}}. {{{ID|}}} Dennis Sciama helped renew interest in Mach's principle with his writings in (among other places) this textbook.
