= Dark matter
{wiki}
<Dark matter> is an inferred gravitating component whose <mass> is not accounted for by the observed luminous material. <Galaxy rotation curves>, motions in galaxy clusters and <gravitational lensing> probe its gravitational contribution through different measurements.<Dark matter by CERN>[Opening discussion: galaxy and cluster dynamics as evidence for unseen gravitating matter]{ref}
For illustration, circular motion in a spherical mass distribution obeys $v_c^2=GM(<r)/r$. A roughly constant <orbital speed> over increasing radius therefore requires enclosed <mass> to keep increasing in this model. A realistic inference also models visible matter and the system's geometry; a rotation curve alone is not a direct identification of a new particle.
<Dark-matter direct detection> searches for interactions in terrestrial targets, while <indirect detection of dark matter> looks for secondary products. These tests address microscopic models rather than replacing the astronomical gravitational evidence.
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