dark matter

Meanings

1. Matter which cannot be detected by its radiation but whose presence is inferred from gravitational effects.
2. Matter which has mass but which does not readily interact with normal matter except through gravitational effects.
3. Unclassified or poorly understood genetic material.

Etymology

The term is often said to have been coined in 1933 by the Swiss astronomer Fritz Zwicky in German (as Dunkle Materie), but it had already been in use for decades, in French (matière obscure) by Henri Poincaré as early as 1906, and in Engish. In contrast to these earlier authors, Zwicky used the term to refer to the apparent mass needed to account for galaxy clusters, where the mass of luminous matter did not add up to enough of a gravitational effect, which led him to infer the existence of nonluminous matter to account for the missing mass. The term gained new popularity in the 1970s as a result of Vera Rubin's publishing (in English) her discovery that some galaxies did not seem to have enough mass to account for their rotation curves.