About 85% of the matter in the universe is in the form of dark matter, whose nature remains a mystery, and the rest is of the kind found in atoms. Dark matter exhibits gravity but otherwise does not interact with normal matter, nor does it emit light. Astronomers studying the evolution of galaxies find that because it is so abundant dark matter does, however, dominate the formation in the universe of large-scale structures like clusters of galaxies.
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Source: Phys.org