Isaac Newton's rotating bucket argument attempts to show that true rotational motion cannot be defined as the relative rotation of the body with respect to the immediately surrounding bodies. It is one of five arguments from the "properties, causes, and effects" of true motion and rest that support his contention that, in general, true motion and rest cannot be defined as special instances of motion or rest relative to other bodies, but instead can be defined only by reference to absolute space. Sir Isaac Newton, (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist, regarded by many as the greatest figure in the history of science. ... In physics, the notion of absolute space underlies the laws of classical physics of Isaac Newton. ...

Background

These arguments, and a discussion of the distinctions between absolute and relative time, space, place and motion, appear in a Scholium at the very beginning of his great work, The Mathematical Principles of Natural Philosophy (1687), which established the foundations of classical mechanics and introduced his law of universal gravitation, which yielded the first quantitatively adequate dynamical explanation of planetary motion. Scholium (tr~bXtoe), the name given to a grammatical, critical and explanatory note, extracted from existing commentaries and inserted on the margin of the manuscript of an ancient author. ... Newtons own copy of his Principia, with hand written corrections for the second edition. ... Classical mechanics is a branch of physics which studies the deterministic motion of objects. ... It has been suggested that this article or section be merged into Gravity. ... ...

Despite their embrace of the principle of rectilinear inertia and the recognition of the kinematical relativity of apparent motion (which under determines whether the Ptolemaic or the Copernican system is correct), natural philosophers of the seventeenth century continued to consider true motion and rest as genuinely contrary predications of an individual body. The dominant view Newton opposed was devised by René Descartes. It held that empty space is a metaphysical impossibility, that space is nothing other than the extension of matter, and that the true motion of a body consists in its transference from the vicinity of bodies immediately surrounding it to the vicinity of other bodies. Descartes recognized that an indicator of true rotational motion is the tendency of the parts of the body to recede from the axis of rotation. Early printed rendition of the Ptolemaic system. ... Heliocentric Solar System Heliocentrism (lower panel) in comparison to the geocentric model (upper panel) In astronomy, heliocentrism is the idea that the sun is at the center of the Universe and/or the Solar System. ... René Descartes (French IPA: ) (March 31, 1596 – February 11, 1650), also known as Renatus Cartesius (latinized form), was a highly influential French philosopher, mathematician, scientist, and writer. ...

The argument

Newton discusses a bucket filled with water hung by a cord. If the cord is twisted up tightly on itself and then the bucket is released, it begins to spin rapidly, not only with respect to the experimenter, but also in relation to the water it contains. Look up bucket in Wiktionary, the free dictionary. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ...

Although the relative motion at this stage is the greatest, the surface of the water remains flat, indicating that the parts of the water have no tendency to recede from the axis of relative motion. Eventually, as the cord continues to unwind, the surface of the water assumes a concave shape as it assumes the spinning motion of bucket relative to the experimenter. This shows that the parts of the water have acquired a centrifugal endeavor despite the fact that they are at rest relative to their immediate surroundings, contrary to Descartes theory.

Having established to his satisfaction that true motion can be understood only in reference to absolute space, Newton remains concerned to address the problem of how it is that we can experimentally determine the true motions of bodies in light of the fact that absolute space is not something that can be perceived. This, he says, can be accomplished by observing the causes and effects of motion as well as the apparent motions of bodies relative to one another, which are the differences of true motions. For example, if two globes, floating in space, connected by a cord that is under tension, with no other clues to assess the situation, measuring the amount of tension in the cord alone suffices to indicate how fast the two objects are revolving around the common center of mass. (This employs an effect of true motion.) Also, the sense of the rotation —whether it is in the clockwise or the counter-clockwise direction— can be discovered by applying forces to opposite faces of the globes and ascertaining whether this leads to an increase or a decrease in the tension of the cord (this employs a cause of true motion). Alternatively, the sense of the rotation can be determined by measuring the apparent motion of the globes with respect to a system background bodies that, according to the preceding methods, have been established not to be in a state of rotation. Globes is a Hebrew language daily financial newspaper, published in Israel. ... Space has been an interest for philosophers and scientists for much of human history. ... Tension is a reaction force applied by a stretched string (rope or a similar object) on the objects which stretch it. ...

See also

• Philosophy of space and time#Absolutism vs. relationalism
• Mach's principle

The examples and perspective in this article or section may not represent a worldwide view. ... In theoretical physics, particularly in discussions of gravitation theories, Machs principle is the name given by Einstein to a vague hypothesis first supported by the physicist and philosopher Ernst Mach. ...

External links

• Newton's Scholium The text from the Scholium of the Principia as translated in 1729 from its original Latin by A. Motte and later translated to 20th century English by F. Cajori
• Newton's Views on Space, Time, and Motion from Stanford Encyclopedia of Philosophy, article by Robert Rynasiewicz. At the end of this article, loss of fine distinctions in the translations as compared to the original Latin text is discussed.
• Life and Philosophy of Leibniz see section on Space, Time and Indiscernibles for Leibniz arguing against the idea of space acting as a causal agent.