Stability of the Solar System that keeps the far side of the Moon away from the Earth. Mercury is in a 3:2 spin–orbit resonance. The planets' orbits are chaotic over longer timescales, such that the whole Solar System possesses a Lyapunov time in the range of 2–230 million years. In all cases this means that the position of a planet along its orbit ultimately becomes impossible to predict with any certainty (so, for example, the timing of winter and summer become uncertain), but in some cases the orbits themselves may change dramatically. Such chaos manifests most strongly as changes in eccentricity, with some planets' orbits
Egdon Heath (Holst) Holst considered the work his most perfectly realised composition, an opinion shared by Ralph Vaughan Williams and others. But it has never had the profile of works such as "The Planets" and "St Paul's Suite". In 1934 Edwin Evans speculated on why the public had not yet shared the composer's assessment: Egdon Heath (Holst) Egdon Heath, Op. 47, H. 172, subtitled "A Homage to Thomas Hardy", is a tone poem by Gustav Holst, written in 1927. Holst considered it his most perfectly realised composition. Egdon Heath is a fictional place in the equally fictional region of Wessex in the south-west