A 1959 theoretical paper by Kahn and Woltjer showed that the Local Group of galaxies can be dynamically stable only if contains an appreciable amount of intergalactic matter
that is not seen .
The Cosmic Origins Spectrograph used for the quasar observations aboard Hubble was designed to probe the evolution of galaxies, stars and intergalactic matter
Silk then tests the big-bang theory, and describes dark matter and intergalactic matter
. He analyzes the possible origin of structures and galaxy formation.
Evolution of galaxies and the intergalactic matter
can be studied by looking at quasar absorption lines.