Updates

Analysing the Six Nations - Week 3

It was all bound to come to an end eventually. After two weeks of correct predictions the model got not one but two wrong in week 3. Let’s have a look at what was predicted versus what actually happened, and spend some time looking in a little more detail at the predictions beyond the point estimate of the scoreline. Yes, it’s time for statistics: it was bound to happen eventually.

How Many Gravitational Waves have we seen? (Spring 2026 Update)

This is the latest update of a post I first write over a year ago which tried to answer the apparently simple question “how many gravitational waves have we detected?”. My last version is now a little out of date, so time for a quick update.

Analysing the Six Nations - Week 2

We’ve had another rollercoaster weekend in the Six Nations, so it’s time to follow-on from my predictions from last week and have a look first of all at how my statistical model faired, and also at what we might expect in the next weekend’s worth of fixtures.

Analysing the Six Nations - Week 1

Way back in 2017 I was trying to learn about a new statistical technique, hierarchical Bayesian inference, using a python package called PyMC. One of the tutorials back then illustrated how to use it to predict football scores, and I thought it would be fun to apply it to rugby. Back then I had a model which looked at historical scores and tried to predict the outcome of future matches just based on those (at some point I’ll write up a more detailed and technical post about how the model works), but this year I’ve been playing around with updating things, and taking into account things like the players actually on the teamsheet each week.

The Mamores in a Gale: Leg 1 Support on an Autumn Ramsay Round

This summer I’ve written “my biggest day in the hills so far” or something of that sort more than in any previous year. To some extent this has been the choice of tough route, big days in Fisherfield and in Knoydart spring to mind. This weekend, however, undoubtedly has the right to this description. With the wind and rain of Knoydart, and the difficulty of Fisherfield and its river-crossings, this is likely to retain the record for a while as well.

In the news - Summer 2025

This summer has been quite a big one for gravitational-wave announcements. I’ve managed to make it into the media once or twice as a result!

Ten Years of Gravitational Wave Detection

Imagine standing in the Albert Hall, and just before the performance begins, as the orchestra is tuning-up, you hear a perfect, virtuosic Mozart melody coming through the noise. Ten years ago, to the day, the world of astronomy (along with the rest of the world) was shaken as the first gravitational waves ever to be detected were measured with the newly-upgraded LIGO detectors. While they were still tuning-up. The gravitaitonal wave took just a fraction of a second to pass through the Earth, but in its wake it created a new field of astronomy.

How Many Gravitational Waves have we seen? (Summer 2025 Update)

Earlier in the year I wrote a post which tried to answer the apparently simple question “how many gravitational waves have we detected?”. Well, with today’s announcement of 128 new detections, it’s time to update my calculations.

GWTC-4.0: introducing 128 new gravitational waves

Today we’re announcing that we’ve more-than-doubled the number of black hole collisions which we’ve observed using gravitational waves. We’re also releasing an enormous amount of data collected between May 2023 and January 2024 which measures tiny changes in the Universe’s geometry measured by gravitational-wave detectors, which are how we identify these collisions. We collect the information about these collisions into publications which we call a “catalog”, which contain all of the information we’re able to extract from the signals we detect and interpret. This includes things like the mass of the objects which were colliding, how fast they were spinning, and whereabouts in the Universe they were. We’ve published earlier versions of this catalogue before now: GWTC-1.0 has events from the first two observing-runs, GWTC-2.0 adds events from the first part of the third observing-run, and GWTC-3.0 events from the second part of that run. GWTC-4.0, which we’ve released today on the arXiv, is the latest version, analysing the first part of our fourth observing run (O4a). The amount of information in these has become so large that we now split the publication describing the catalog into three parts: an introduction paper, a paper describing the methods used in the analyses, and the results of those analyses. I’ve had the pleasure of leading a team which performed one of these analyses (the “parameter estimation” analysis), which takes signals which have been identified in the data and then works out the properties of the black holes and neutron stars which produced them. It took around 60 of us to do this (and there’s more about that later in this post). I then took-over as the editor of the results part of the catalog publication in June. It’s quite nice to know that I’ve joined a bit of a Glasgow tradition of doing this: my line-manager John Veitch was responsible for GWTC-2.0, and my colleague Christopher Berry for GWTC-3.0. I can only apologise to either of them if I ever thought they seemed to have an easy job!

Wilderness Untamed

I often find myself wondering why I climb hills, why I’m not prepared to enjoy normal holidays which involve pottering around pretty towns, lying on the beach, or visiting theme parks. I think my experiences of almost two weeks far north of the Great Glen, in the hills vaguely close to Ullapool, helped to answer that question for me: it’s clearly a feeling of achievement, of going somewhere only a tiny fraction of the population will ever go. Why I insist on having this feeling of achievement while also walking through the driving rain, however, is still an open question. But in the hours I spent in Fisherfield, alleged to be Scotland’s only real wilderness, I asked myself this question many, many times.

• Beinn a' Chlaidheimh 913 m Corbett
• Sgurr Ban 989 m Munro
• Mullach Coire Mhic Fhearchair 1015 m Munro
• Beinn Tarsuinn 933 m Munro
• A' Mhaighdean 967 m Munro
• Ruadh Stac Mor 918 m Munro

How Many Gravitational Waves have we seen?

Last week I got an email from a colleague, asking a question which, on the face of it, should have been easy to answer.

Going Beyond GWTC-3

It started as a nice, simple, short project to test some code I was working on. Things… got out of hand. Today I’ve submitted a paper describing a project I’ve been working on for around 18 months, which was not initially planned as a paper.

The half-life of a flood

Lately I’ve been going through lots of little half-finished analyses and trying to write them up in some form. Today it’s my attempt to answer the question “how long does a river stay in spate?”. The primary motivation of this being that when the water level on the Clyde is high it’s not safe to row on it. Clubs, such as Clyde ARC might want to have an idea of how long it will be before the water level is low enough that it’s safe.

What's a good marathon time?

I seem to be incapable of just doing something without wondering about the statistics behind it these days.

An update on the maps

A couple of weeks ago I posted some images from a new map I’d been working on. The motivation behind this was mostly curiosity, though I’ve been dabbling with trying to do things like this in python for a while, before realising that implementing hill-shading was probably more effort than it was worth, and turning to a tool actually designed for this: QGIS.

Messing about with Maps

It’s been a while since I posted anything, and I have a big backlog of things to write-up and add to this site. In the meantime, enjoy some maps I’ve made (with the ultimate intention of eventally using them on my route descriptions on the site!).

What did we learn in O3? (Part 1)

I started this post with the idea of summarising all of the new science which has resulted from observations made up to the end of the third observing run of the advanced LIGO and Virgo detectors. It turns out there’s rather a lot, so this looks like it’ll be the first of several! I’ve tried to include links to as many papers as possible.

asimov 0.5.4

I’m pleased to announce the release of the latest version of asimov.