Time slows down for no quasar
Space has been expanding since the big bang, stretching light from distant objects to longer, redder wavelengths--a process called "red shift". The expansion means that distant events appear to occur more slowly than those nearby. For example, the interval between light pulses leaving a faraway object once per second should have lengthened by the time they reach Earth because space has expanded during their trip. Supernovae show this time dilation in the speed at which they fade--far-off explosions seem to dim more slowly than those nearby. But when Mike Hawkins of the Royal Observatory in Edinburgh UK, looked at light from quasars he found no time dilation. Scott Gaudi of Ohio State University in Columbus says this explanation does not square with microlensing observations of the Milky Way, which suggest that no wore than 20% of the galaxy's dark matter halo can be made up of massive, compact objects such as primordial black holes.
