I'm in a strange kind of limbo at the moment. I'm not being paid, since I can't sign my new contract without being physically present in Spain. And, until the 30th of March, it was physically impossible to enter Spain unless you were a Spanish resident, since the borders were closed due to Covid restrictions. …
Continue reading Daily: using a Jupyter notebook to make presentation slides
I started this morning in unusually energetic fashion, by going for a run before starting work. It was a bit chilly but the sky was clear blue and the sun was shining. The birds were singing and the blackthorn blossom has topped the newly green trees and hedges with a creamy white glaze. The daffodils …
Continue reading Daily: running, paper revisions, talk writing
I've decided it's time to improve the consistency of my writing and practice makes perfect, as they say. So, starting from today, I'm going to a write a blog post every day for thirty days (excluding weekends and holidays). By my calculation, this means the last post in the thirty day sequence will come on …
In this post, I'll discuss how I prepared for my PhD viva exam in cosmology, what the viva itself was like and what happened next. I submitted my PhD thesis on the 4th of January 2021 (which also happened to be my birthday) and had my viva exam on the 3rd of February. This is …
How do you write a PhD thesis? This question sounds like the start of the old joke: "How do you eat an elephant? One piece at a time". A PhD thesis is a document which must explain, summarise and defend three or more years of research in your chosen field, often running to 40,000 words …
As we frequently hear1, we're now in the precision era of cosmology. What this really means is that we're in the era of measuring things really well, and we're getting really good at measuring things because we keep building ever more enormous and powerful telescopes. I remember attending the STFC Introductory Summer School on Astronomy …
Continue reading Thesis off-cuts: the reproducibility crisis in cosmology
Thanks to many hundreds of people making dedicated observations of the sky over many decades, we know that the majority of our Universe is comprised of two substances: dark matter and dark energy. Dark matter is an unknown type of matter, referred to as "dark" because it does not interact electromagnetically, meaning that it doesn't …
Continue reading Thesis off-cuts: how special is our place in the Universe?
The distance duality relation tells us how, assuming that photons propagate on null geodesics in a pseudo-Riemannian spacetime and that their number is conserved, luminosity and angular diameter distances are related, via where dL is the luminosity distance, dA the angular diameter distance and z the redshift. This relation was introduced by Etherington in 1933, …
Last week, a tweet by Roberto Trotta drew my attention to a recent paper by Simon Portegies Zwart that studied the amount of carbon dioxide emitted by running N-body simulations in different programming languages. https://twitter.com/R_Trotta/status/1309457430267523072 The figure that caught my attention was Figure 3, copied below from the version of the paper published in Nature …
My early efforts at blog writing were somewhat sporadic, but I did mark some key moments during my PhD, in the posts Year Two and Year Three. In the former, I reflected on the major review that every Portsmouth PhD student must pass in order to progress to their second year. In the latter, I …
