When its initial distribution is seeded by the cosmic microwave background, it gives an explanation 
When its initial distribution is seeded by the cosmic microwave background, it gives an explanation for large-scale structure formation, and gravitational lensing of the Bullet cluster provides evidence for it. The current (*) cosmological standard model favors a "cold" variety of it, and it's first proposed by Fritz Zwicky based on his study of rotational velocities of galaxies. For 10 points― name this substance, candidates for which include WIMPs, and which is named for its lack of electromagnetic interactions.
When its initial distribution is seeded by the cosmic microwave background, it gives an explanation for large-scale structure formation, and gravitational lensing of the Bullet cluster provides evidence for it.
dark matter (do not accept or prompt on “dark energy”)