...Principia.^2.1

An excellent discussion of the historical development of Newtonian mechanics, as well as the physical and philosophical assumptions which underpin this theory, is given in Barbour 2001.

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... (acceleration).^2.2

A scalar is a physical quantity that is invariant under rotation of the coordinate axes. A vector is a physical quantity that transforms in an analogous manner to a displacement under rotation of the coordinate axes.

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... Sun.^5.1

Precession can be either prograde (in the same sense as orbital motion) or retrograde (in the opposite sense). Retrograde precession is often called regression.

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... 1995).^6.1

Actually, the Earth's rotation period relative to the distant stars is called a stellar day, whereas a sidereal day refers to the Earth's rotation period relative to the vernal equinox (which is a misnomer, because “sidereal” means stellar.) A sidereal day is approximately $8.4$ ms less than a solar day, so the distinction between the two is irrelevant for most purposes.

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... elements.^10.1

In mathematical terminology, two curves are said to osculate when they touch one another so as to have a common tangent at the point of contact. From the Latin osculatus, “kissed.”

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... years.^11.1

This precession rate is about $10^{\,4}$ times greater than any of the planetary perihelion precession rates discussed in Sections 5.4 and 10.3.

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... month.^11.2

A synodic month, which is $29.53$ days, is the mean period between successive new moons.

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