dark matter

pimeä aine puhekieltä Particles of matter that cannot be detected by their radiation but whose presence is inferred from gravitational effects.
2001, Susan M. Fitzpatrick, John T. Brue, http://books.google.com.au/books?id=otGR49vOGtYC&pg=PT192&dq=%22dark+matter%22+-intitle:%22dark+matter%22&hl=en&ei=OE3VTb2PHo6IvgPXxt2mDA&sa=X&oi=book_result&ct=result&resnum=6&ved=0CFEQ6AEwBQv=onepage&q=%22dark%20matter%22%20-intitle%3A%22dark%20matter%22&f=false Carving Our Destiny: Scientific Research Faces a New Millenium,

The evidence for dark matter in galaxies started to accumulate in the mid-1970s. By the following decade it became clear that essentially all galaxies, including our own Milky Way, are surrounded by extensive halos of dark matter.

On large scales like that of clusters of galaxies, gravitational lensing indicates that the dark matter is smoothly distributed, on the average.