Old and New Results from the CMB

In the first part of this colloquium, I will assume that you've all seen quite a few talks on the recent Planck results, and so concentrate on some of the less well-known results. In particular, I will concentrate on what Planck can say about the very large-scale structure of spacetime: the background geometry and topology of the Universe. Deviations from the homogeneous and isotropic FRW cosmology are theoretically and (still) observationally possible. Planck finds no evidence for either a topologically connected Universe nor an anisotropic cosmology, although a Bianchi VIIh cosmology (with the "wrong" cosmological parameters) seems to fit some of the so-called large-scale anomalies seen in the CMB intensity pattern. In the second part, I will talk about some of the ongoing efforts to measure the CMB from the ground and balloons, using not just tens of detectors as with Planck, but with thousands, enabling much higher sensitivity measurements of CMB polarisation. These have already begun to bear fruit: I shall discuss Polarbear's recent observations of the effect of lensing on the CMB polarisation pattern, including the first direct detection of the CMB B-mode power spectrum.