Dark matter—A personal view

Traditional evidence for large amount of dark matter is based on dynamical consideration for systems with tdyn≫tobs. Recent observational and theoretical developments in gravitational lensing offer a much more robust determination of the mass distribution in some galaxies and their clusters, with the precision comparable to that obtainable for double stars for which tdyndirect evidence for the presence of dark matter. Gravitational microlensing and femtolensing offer a possibility to detect MACHOs with masses in excess of ∼10−15 M⊙. The recent detections of microlensing events by the EROS, MACHO and OGLE teams do not require any dark lenses as ordinary low mass stars are compatible with the observations. However, these searches will soon either detect genuine MACHOs, or they will place stringent upper limits on their number density.