Research

Cosmic history plotted logarithmically, showing a timeline of key events. The generation of fingerprints of the physics which gave rise to cosmic structure, and the cosmological probes in which we see these signatures, are labelled. The vertical red line marks the release of the cosmic microwave background (CMB), the earliest light we can observe in the universe. Adapted from J. McMahon; do not reproduce without permission.

 

The key events in the history of the universe are shown in this schematic, designed to emphasize where our understanding of physics is most lacking. White corresponds to the physics of baryons and radiation which, while exhibiting complex non-linear behaviour on macroscopic scales, are extremely well-described by the Standard Model of particle physics on microscopic scales. However, both at early and late times, there are huge gaps in our understanding. At late times, we do not have a physical understanding of what 96% of our universe is made of. Our physical understanding also fails as we look back at earlier times and higher energies. The Large Hadron Collider (LHC) is designed to achieve a maximum beam energy of 7 TeV. Significantly above this energy scale, we have no way to test physics in the laboratory. Yet, without understanding physical processes at energies a trillion times higher than reached by the LHC, we cannot hope to unravel the origin of all the structure in the universe.

The universe is 13.7 billion years old. The earliest light we can see in the universe is the cosmic microwave background (CMB), which was released 380,000 yrs after the Big Bang. The slight variations in the CMB temperature reflect initial inhomogeneities in the radiation and matter that later collapsed due to gravity to form clusters and galaxies. The CMB and the distribution of galaxies encode rich statistical information about much earlier times and much higher energies – about the physical mechanism that originated cosmic structure. The goal of our research is to use the early universe – as revealed by the CMB and galaxy surveys – as a “laboratory” to uncover the physics that powered the Big Bang.