What is the role of dark matter in the universe?

The role of dark matter in the universe is primarily that it interacts through gravity but does not emit light, making it invisible to standard detection methods. This property is crucial because dark matter's gravitational pull affects the behavior of galaxies and galaxy clusters. Observations of the rotation curves of galaxies reveal that they rotate at such speeds that, without the gravitational influence of additional mass, they would tear apart. Dark matter provides that extra mass, ensuring galaxies remain intact.

In terms of cosmic structure formation, dark matter plays a pivotal role. It acts as a scaffolding for ordinary matter, allowing gas and stars to clump together and form galaxies and other large structures. The existence of dark matter helps explain the observed distribution of galaxies in the universe and their motion within galaxy clusters.

The other options suggest misunderstandings about the properties and effects of dark matter. For example, while dark energy is responsible for the acceleration of the universe's expansion, dark matter does not emit radiation detectable by telescopes, which is why it remains elusive and only inferred through its gravitational effects. Additionally, while dark matter facilitates the formation of galaxies, it does not primarily cause their formation, as actual star formation involves baryonic (normal) matter interacting through electromagnetic forces.