New Haven, Conn. -- The universe's funhouse mirrors are revealing a difference between how dark matter behaves in theory and how it appears to act in reality.

Dark matter is the invisible glue that keeps stars bound together inside a galaxy. It makes up most of a galaxy's mass and creates an invisible scaffold that tethers galaxies to form clusters.

Dark matter does not emit, absorb, or reflect light. It does not interact with any known particles. Its presence is known only through its gravitational pull on visible matter in space.