Remote outreach talk to the Newcastle Astronomical Society, given by Alex Gough

The Skeleton of Our Universe

The goal of this talk is to introduce the topic of my research, understanding the largest structures in the universe, to the members of the Newcastle Astronomical Society. This begins by setting the stage for where cosmology takes place, and winding back the cosmic clock to the early universe and the cosmic microwave background (CMB). From there, understanding that the very early universe is nearly the same everywhere, with only 10 parts per million deviation from the mean density, it becomes an obvious scientific question to understand how those tiny fluctuations grow into the rich structure of galaxies we see today. Understanding this growth, and the role dark matter has to play in it, is the focus of my research.

After touring through the history of the universe, we take a detour into understanding how these huge distances and times are actually measured. This detour provides a link from my work in cosmology to the stellar physics and observations that members of an astronomical society are more familiar with. It also provides a nice opportunity to look at beautiful space pictures.

The end point of the talk is the 6 numbers one needs to measure to construct the universe. These are based on the 6 parameters in ΛCDM (the standard cosmological model), slightly modified to make them more accessible to this general audience. These break down into:

• 2 numbers from the early universe: the amplitude and scale dependence of the fluctuations in the CMB
• 2 numbers for the “pie recipe” of the universe: how much dark energy and dark matter do we have
• 2 timescales for the universe: the age of the universe, and the time you have to wait for the first stars to form.