WHAT IS DARK MATTER?
Dark matter does not emit, absorb, or reflect light. Its presence is only known through its gravitational pull on visible matter in space. Therefore, dark matter remains as elusive as Alice in Wonderland's Cheshire Cat – where you only see its grin (in the form of gravity) but not the animal itself. One way astronomers can detect dark matter is by measuring how its gravity distorts space, an effect called gravitational lensing. Dark matter, although invisible, makes up most of the universe’s mass and creates its underlying structure. Dark matter’s gravity drives normal matter (gas and dust) to collect and build up into stars and galaxies. Although astronomers cannot see dark matter, they can detect its influence by observing how the gravity of massive galaxy clusters, which contain dark matter, bends and distorts the light of more-distant galaxies located behind the cluster. As seen in this image, large galaxy clusters contain both dark and normal matter. The immense g...
