Abstract

Observations of the cosmic microwave background radiation by the European Space Agency’s Planck satellite have led to a standard model of cosmology with very precisely determined parameters. In this model, known as LCDM , structure in the Universe arose from quantum fluctuations that were stretched in scale during an early inflationary phase in the Universe’s history. At the present day most of the matter is cold and invisible, but most of the energy is in an unusual form that is also dark and invisible. I will first discuss, from a personal perspective, how we got to the LCDM model. I will then ask whether we have actually learned anything, given that the three key ingredients of the LCDM cosmology – inflation, cold dark matter and dark energy – are not understood at a fundamental level. I will then speculate on whether there is likely to be a new paradigm shift in cosmology within the next few years.