Gravitation, the universal attractive force, acts upon all matter(and radiation) relentlessly. Left to itself, gravity wouldpull everything together, and the Universe would be nothingbut a gigantic black hole. Nature throws almost every bit ofphysics – rotation, magnetic field, heat, quantum effects andso on, at gravity to escape such a fate. In this series of articles,we shall explore systems where the eternal pull of gravity hasbeen held off by one or another such means.

Gravitation, the universal attractive force, acts upon all matter(and radiation) relentlessly. Stable extended structurescan exist only when gravity is held off by other forces of nature.This series of articles explores this interplay, looking atobjects that just missed being stars in this particular installment.

During its active lifetime, a star burns its nuclear fuel, andgravitation is held off by the pressure of the heated gas. Gravityshould take over once this fuel is exhausted unless someother agency saves the star from such a fate. Low mass starsfind peace as ‘white dwarfs’ when the electrons settle intoa Fermi degenerate phase where the pressure of degenerateelectrons balance the gravitational pressure.

A star burns its nuclear fuel and balances gravitation by thepressure of the heated gas, during its active lifetime. Afterthe exhaustion of the nuclear fuel, a low mass star findspeace as a ‘white dwarf’, where the pressure support againstgravitation is provided by Fermi-degenerate electrons. However,for massive stars, the gravitational squeeze becomes sosevere that in the final phase of evolution, the average densityapproximately equals the nuclear density. At such densities,most of the protons combine with electrons to convertthemselves into neutrons. A `neutron star', composed of suchneutron-rich material, is host to some fascinating physics arisingout of its amazingly compact state of matter (where a solarmass is packed inside a sphere of radius ∼ 10Km).

Both, human appreciation of music and musical genres transcend timeand space. The universality of musical genres and associated musicalscales is intimately linked to the physics of sound, and the specialcharacteristics of human acoustic sensitivity. In this series ofarticles, we examine the science underlying the development of theheptatonic scale, one of the most prevalent scales of the modernmusical genres, both western and Indian.

A set of basic notes, or ‘scale’, forms the basis of music. Scalesare specific to specific genre of music. In this second articleof the series, we explore the development of various scalesassociated with Western classical music, arguably the mostinfluential genre of music of the present time.

In the previous articles of this series, we have discussed thedevelopment of musical scales particularly that of the heptatonicscale which forms the basis of Western classical musictoday. In this last article, we take a look at the basic structureof scales used in Indian classical music and how differentragas are generated through the simple process of scaleshifting.