This being the first talk/article of the conference, I begin with a brief reminder of what we are currently trying to achieve in cosmology. Personally, I'm interested in the following overall goals:
Over recent years, much progress has been made on all of these topics, to the extent that it is widely believed amongst cosmologists that we may stand on the threshold of the first precision cosmology, in which the parameters necessary to describe our Universe have been identified and, in most cases at least, measured to a satisfying degree of precision. Whether this optimism has any grounding in reality remains to be seen, though so far the signs are promising in that the basic picture of cosmology, centred around the Hot Big Bang, has time and again proven the best framework for interpretting the constantly improving observational situation.
In particular, the process of cosmological parameter estimation is well underway, thanks to observations of distant Type Ia supernovae, of galaxy clustering, and of the cosmic microwave background. These have established a standard cosmological model, where the Universe is dominated by dark energy, contains substantial dark matter, and with the baryons from which we are made comprising only around 5%. Overall this model can be described by around ten parameters (e.g. see Wang et al. ), and the viable region of parameter space is starting to shrink under pressure from observations. However, it is worth bearing in mind that we seek high precision determinations at least in part because they ought to shed light on fundamental physics, and there progress has been less rapid. Some parameters are likely to have no particular fundamental importance (for instance, there would probably be little fundamental significance were the Hubble constant to turn out to be 63 km s-1 Mpc-1 rather than say 72 km s-1 Mpc-1), but the 10% or so measured accuracy of the baryon density is to be set against the lack of even an order-of-magnitude theoretical understanding thus far.