interview with a Fellow
Dr Cora Uhlemann The cosmologist studying the dark ages of our Universe
I
grew up in central Germany, in Gera, a city in the federal state of Thuringia. In 2007 I moved to Munich to study Physics at the city’s Technical University. Both of my parents had also studied Physics at university although my mother wasn’t too keen I follow in their footsteps! She would have preferred for me to read Engineering which, funnily enough, my sister ended up studying. Whilst studying Physics, I realised that I really enjoyed its maths component so I ended up also studying Mathematics at the nearby Ludwig Maximilian University. LMU was then my academic home until 2015, when I finished my PhD in Cosmology. My cosmological research tries to describe the skeleton of all the matter in the Universe and how it formed. A sort of baby picture of the Universe. The earliest snapshot we have is from around 13 billion years ago and there isn’t much there. In the beginning, the Universe was very hot and light was ‘trapped’ by scattering in plasma. This early Universe is opaque and can’t be
P26 FITZWILLIAM COLLEGE NEWSLETTER
observed directly. After a long time (about 380,000 years), the Universe cooled down leading to the formation of neutral atoms. Their presence meant that light was no longer scattered, but instead was able to travel through them. Some part of the white noise/static on our TVs today comes from this afterglow of the early universe, called the ‘cosmic microwave background’! Until about 1 billion years, this was almost all the light in the universe; we call this period the Dark Ages. During this time, dark matter gradually gathered and finally traced out a large-scale skeleton-like structure. In particularly dense regions, this led to the gradual emergence of stars and galaxies, and the Dark Ages were no more.
My latest paper, ‘Cylinders out of a top hat’*, looks at how many galaxies we can find within circular patches on the sky. I always try to come up with funny titles for my articles although some colleagues have told me it’s a silly thing to do, even if it helps them remember the title and paper more easily!
Scientists have yet to agree on the timing of the earliest galaxy formation although we know it’s less than one billion years after the Big Bang. The most common misconception about my field is that ‘it’s just a theory’. It is a theory, but one that can fit several independent observations from different epochs with one set of parameters!
2016 Nobel Laureate Meeting for Physics: I presented my PhD research as part of the event’s ‘Bavarian evening’, which is why I was wearing a traditional ‘dirndl’ dress