Dark Matter

Understand

A review of the development of the concept of dark matter is given.

• I begin the review with the description of the discovery of the mass paradox in our Galaxy and in clusters of galaxies.
• In mid 1970s the amount of observational data was sufficient to suggest the presence of a massive and invisible population around galaxies and in clusters of galaxies.
• The nature of the dark population was not clear at that time, but the hypotheses of stellar as well as of gaseous nature of the new population had serious difficulties.