186th International School of Physics "Enrico Fermi" : New Horizons for Observational Cosmology

This school comes at a unique time in cosmology. Our understanding of the universe has been revolutionized by observations of the cosmic microwave background (in particular Wilkinson Microwave Anisotropy Probe), the large-scale structure of the universe (Two-degree-Field Galaxy Redshift Survey and Sloan Digital Sky Survey), and distant supernovae. These studies have conclusively shown that we are living in a strange universe: 96% of the present-day energy density of the universe is dominated by the so-called dark matter and dark energy. However, we do not know what dark matter and dark energy actually are. The data also suggest that it is likely that the universe underwent a rapid accelerating expansion phase in the very early universe called the inflationary phase. However, we still do not know how inflation happened.