Explore the intricacies of de Sitter space in this advanced physics lecture delivered by Dionysios Anninos from King's College London. Delve into the classical and quantum aspects of asymptotically de Sitter spacetimes, examining the late-time de Sitter wavefunction and the dS/CFT correspondence. Investigate a concrete example involving Vasiliev theory with its infinite tower of interacting massless gauge higher spin fields. Compare and contrast the cosmological dS horizon with a standard black hole horizon. Topics covered include semi-classical gravity, functional determinants, gauge redundancy, differences between DS/CFT and ADS/CFT, higher spins in DS, classical EOM Vasiliev, infinite dimensional symmetry, and wave functions. Engage with complex theoretical concepts and participate in an exercise to reinforce understanding of this cutting-edge area of string theory and cosmology.