What are the links between high energy particle physics and cosmology?
Much astronomical evidence (particularly the galactic red shifts for which Hubble is famous and the ubiquitous 3 Kelvin background microwave radiation in the sky (Penzias and Wilson, more recently the cosmic background explorer COBE)) point to a ‘Big Bang’ about 13 billion years ago. At that time, the universe was extremely dense and hot. Let’s imagine going backwards in time towards t =0. As the temperature gets higher, the typical energy due to thermal motion (kT, where T is the absolute temperature and k is Boltzmann’s constant) gets greater. When it becomes comparable with the ionization energy of hydrogen (kT ~ 10 eV), nuclei can no longer hold on to the electrons and so there are no longer atoms, just a plasma. Keep going back in time, hotter and hotter. Eventually the protons are colliding with each other with the same sorts of energies produced in the big atom smashers (kT ~ GeV), and so all of the weird particles recorded at e.g. CERN are now present in the tiny, dense univers
