I've spotted a couple of BBC News articles about dark matter over the last several days. It seems we're learning more about it, even if we still have no idea what it is.
First article:
Dark matter map unveils first resultsAn international group has been mapping the dark matter density in a section of the sky, in detail. This involves careful analysis of photographs to identify gravitational lensing effects, and then work out where the mass has to be to cause the observed effects. They have now released their first results, covering 0.4% of the sky; eventually they will work up to one-eighth (12.5%). This map should also give us more information about dark energy.
Second article:
Dark matter becomes less 'ghostly'Another group have done a similar density mapping exercise on a a small galactic cluster where the galaxies are colliding. They found that with one of the galaxies, they found that the dark matter was lagging behind the visible matter. This implies that the dark matter is undergoing some sort of interaction with itself that is not gravitational - the first hint that there is an interaction of this sort.
From my perspective, this feels like a very exciting time to be active in fundamental physics and cosmology. It feels very reminiscent of the state of physics around the year 1900: we have a lot of evidence for interesting things (dark matter and dark energy now; relativistic and quantum effects then) but no theory to explain them. When will we get another Newton or Einstein with the insight to explain it all?
