An Etymological Dictionary of Astronomy and Astrophysics
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Philosophy: A doctrine according to which the virtue of a thing or an action is determined by its utility. The goal of utilitarian ethics is to promote the greatest happiness for the greatest number of people. The founders of this philosophical school were Jeremy Bentham (1748-1832) and James Mill (1773-1836).

→ utilitarian; → -ism.

A mechanism proposed by Eddington to explain → stellar pulsations. Same as the → kappa mechanism. In this analogy the stellar layer acts like a heat engine with radiation taking the role of stream. The expanding and contracting layer acts as the piston, and the opacity of the layer behaves as the valve mechanism (Eddington, 1917, The pulsation theory of → Cepheid variables, The Observatory 40, 290).

→ valve; → mechanism.

An optical device for producing and analyzing polarized light. It divides incoming unpolarized light into two orthogonal, linearly polarized beams. It consists of two prisms of either quartz or calcite cemented together.

After the English scientist William Hyde Wollaston (1766-1828); → prism.