De motu corporum in gyrum (On the motion of bodies in an orbit) is a manuscript by Isaac Newton sent to Edmund Halley in November 1684. It derived the three laws of Kepler assuming an inverse square law of force, and generalized the answer to conic sections. It tried to set out the foundations of modern dynamics and extended its methodology by adding to the derivation of Kepler's laws the solution of a problem on the motion of a body through a resisting medium. Halley reported these results to the Royal Society on 1684-12-10 (Julian calendar). Three versions of the manuscript exist: they differ from each other in some crucial respects. The book Principia Mathematica is a correction and an expansion of this note. Sir Isaac Newton in Godfrey Knellers 1689 portrait Sir Isaac Newton (25 December 1642 – 20 March 1727 by the Julian calendar in use in England at the time; or 4 January 1643 – 31 March 1727 by the Gregorian calendar) was an English physicist, mathematician, astronomer, philosopher, and alchemist who... Edmond Halley. ... Events France under Louis XIV makes Truce of Ratisbon separately with the Empire and Spain. ... Events France under Louis XIV makes Truce of Ratisbon separately with the Empire and Spain. ... December 10 is the 344th day (345th in leap years) of the year in the Gregorian calendar. ...

Two important definitions in the first version of this work are worth drawing attention to in the light that they throw on the development of Newton's thoughts on dynamics—

1. that of centripetal force, accepting totally the tutorial on the role of inertia in circular motion given by Robert Hooke in his letter of 1674,
2. that of force inherent in a body which forces it to move in a straight line, showing that the nature of inertia was still not clear.

This error was further compounded by adding this inherent force to an external force by the parallelogram law. Robert Hooke (July 18, 1635 - March 3, 1703), one of the greatest experimental scientists of the seventeenth century, played an important role in the scientific revolution. ... Events February 19 - England and the Netherlands sign the Treaty of Westminster. ...

The first version was reported to the Royal Society, but was not published since Newton wanted to revise it. The second version (possibly dating from December or January) contained minor corrections. The last version of this note attempts a reconstruction of dynamics by stating five laws of dynamics —

Law 1

stated that a body moved uniformly by inherent force alone.

Law 2

asserted that the "change in the state of moving or resting is proportional to" the impressed force and is made in the direction of the line in which the force acts.

Law 3

held that the motion in a given space did not depend on any rectilinear uniform motion of that space.

Law 4

stated that mutual interactions of bodies do not change the motion of their center of mass.

Law 5

contained an empirical statement about the resistance of media.

In addition he added to this last version an explicit hypothesis about an absolute frame of reference, with respect to which the motion of bodies could be determined: this in spite of already undermining this notion by the above Law 3.

Two separate papers of revision followed the last version of De motu. In these he reduced the number of laws of motion to 3. He sharpened the law of inertia without giving up an inherent force, but introduced a distinction between inherent and impressed force, clarifying that the latter only changes the motion of the body, but is not added to the inherent force. The inherent force disappeared in the Principia Mathematica. For Isaac Newtons 1687 book containing basic laws of physics, see Philosophiae Naturalis Principia Mathematica The Principia Mathematica is a three-volume work on the foundations of mathematics, written by Bertrand Russell and Alfred North Whitehead and published in 1910-1913. ...

See also

• Isaac Newton, Galileo, Descartes, Robert Hooke and Christian Huygens
• Principia Mathematica and classical mechanics

Sir Isaac Newton in Godfrey Knellers 1689 portrait Sir Isaac Newton (25 December 1642 – 20 March 1727 by the Julian calendar in use in England at the time; or 4 January 1643 – 31 March 1727 by the Gregorian calendar) was an English physicist, mathematician, astronomer, philosopher, and alchemist who... Galileo can refer to: Galileo Galilei, astronomer, philosopher, and physicist (1564 - 1642) the Galileo spacecraft, a NASA space probe that visited Jupiter and its moons the Galileo positioning system Life of Galileo, a play by Bertolt Brecht Galileo (1975) - screen adaptation of the play Life of Galileo by Bertolt Brecht... René Descartes René Descartes (IPA: , March 31, 1596 – February 11, 1650), also known as Cartesius, worked as a philosopher and mathematician. ... Robert Hooke (July 18, 1635 - March 3, 1703), one of the greatest experimental scientists of the seventeenth century, played an important role in the scientific revolution. ... Christiaan Huygens Christiaan Huygens (approximate pronunciation: HOW-khens; SAMPA /h9yGEns/ or /h@YG@ns/) (April 14, 1629–July 8, 1695), was a Dutch mathematician and physicist; born in The Hague as the son of Constantijn Huygens. ... For Isaac Newtons 1687 book containing basic laws of physics, see Philosophiae Naturalis Principia Mathematica The Principia Mathematica is a three-volume work on the foundations of mathematics, written by Bertrand Russell and Alfred North Whitehead and published in 1910-1913. ... In physics, Classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the motions of bodies, and the forces that cause them. ...

References

• Never at rest: a biography of Isaac Newton, by R.S. Westfall, Cambridge university press, 1980 [ISBN 0521231434]