For 10 points, name this adjective that describes matter and energy undetectable by electromagnetic radiation and thought to compose most of the universe.
This adjective describes a phenomenon that causes galaxies to move towards the Hydra-Centaurus Supercluster. Axions may be a "cold" substance described with this adjective, while neutrinos may be the "hot" form of that substance. This word also describes a period before the first neutral matter was formed. An agent described by this word is proposed as the cause of the accelerating expansion of the universe, and a substance described by this word is thought to be made up of weakly interacting massive particles. For 10 points, name this adjective that describes matter and energy undetectable by electromagnetic radiation and thought to compose most of the universe.
This adjective describes a phenomenon that causes galaxies to move towards the Hydra-Centaurus Supercluster.
dark [accept any of dark matter, dark energy, Dark Ages, dark flow]