I’ve finally finished the project.
When looking into the most recent papers, it seems there’s a general consistency in the data between values of H0. I was really expecting a lot of variation in this, but this seems to have settled down over the past few years, and there’s general agreement on a value of around 71 or 72.
Yet this only works with the data from Gravitational Lensing if we model the mass of the galaxy in line with the observed light of the galaxy. This sounds ok, but is in direct conflict with dark matter theories – where we believe 90% of a galaxy’s mass must lie outside the visible disc, in a large near-spherical halo. If they take dark matter into account, the GL figures are all ~10% too low – and there’s too much agreement between other methods (WMAP, Chandra, HST Key Project) to allow that.
So really, GL is offering information on dark matter rather than on the Hubble Constant, which is quite a surprise. Hopefully the report has made that clear.
I’ve had a week off work to finish up, and it’s been a long time since I’ve been able to work on the project, so it’s been a busy week! I’ve had to catch up on stuff I already knew, and I know the report isn’t as polished as I would have liked. But it should hit all the targets.