Latest

The colleges of Oxford

I have now been at Oxford for quite a while but I must confess to not having been a very good tour guide. I knew next to nothing about the colleges other than the handful I had personal experience with. So, I decided to open up each of their Wiki

Local mesoscale kinetic energy flux in the atmosphere - Preprint

Below is a link to a preprint of my paper. This will be replaced by the DOI when accepted. Local mesoscale kinetic energy flux in the atmosphere PreprintLocal mesoscale kinetic energy flux in the atmosphere Preprint.pdf3 MBdownload-circle Abstract The mesoscale atmospheric energy spectrum has puzzled scientists for decades, sitting

How I contributed to a 40 year mystery

As a PhD student, I published a paper with my amazing supervisors at Oxford and my wonderful collaborators at the University of Rochester, in particular Ben Storer. In plain English, this is what it was about. After taking a hot shower, have you ever paused to watch the swirling shapes

A video on convolutions

I decided to make a short video on how to see the convolution operation intuitively!

I made a video about relativity

I just made my first proper youtube video. I think there is a lot of room for improvement, but I am happy with the physics, and maybe you will be too:

Kepler's laws

In this blog, I wanted to trace the history of how we came to know three neat facts about the motion of the planets. These three facts are known as Kepler’s laws, and they are rather beautiful observations that led to the development of classical physics. We will wander

Are fingerprints symmetric?

While I was in the library, staring into my hands, wondering why I thought a PhD was a good idea, I noticed something for the first time.  My fingerprints were symmetric between hands. Looking closer, I could tell that the details of the valleys and ridges differed between the fingers,

And yet it spins...

Galileo Galilei was the first person to observe the moons of Jupiter. He saw objects in the sky that clearly orbited something other than the Earth. This observation can lead to a radical thought: Could the Earth be like those moons, could the Earth be orbiting something? Galileo was persecuted

What a mess!

There has been a lot of talk of carbon capture recently since it appears we will not be able to slow down burning fossil fuels anytime soon. So far humans have released 2500 billion tonnes of CO2 into the atmosphere since heavy industrialisation began. I just wanted to think a

I was in an advert

My PhD program put out a call for people to be in an advert and I accepted. I spent a day being made to feel like a celebrity by Joy of Angel Sharp Media. I'm really impressed with how good they managed to make us look! If anyone

Kills 99.9% of germs

You have likely seen this marketing phrase on disinfectant before, but what does it mean? Does it mean that of all the germs that exist, the product can kill 99.9% of the varieties?  Not quite. Let’s indulge a little and dive into this. First of all, what’s

Creating a novel chaos game

The concept of self-organised criticality (SOC) was invented in the late 80s. The idea is that a system can naturally evolve towards a critical point and then stay there. The example first used to introduce the idea was called the sandpile model. The sandpile model is a cellular automata with

Magnetic pendulum choice maker

Chaos is fascinating. Where a released pendulum will end up around magnets is incredibly complicated. You can explore this in a fantastic interactive visualisation from Ingo Berg. I decided a decision-making app where each magnet represented something you wanted to decide between, would be a fun project. Click the black

Game of life writer

Play This JavaScript app converts text into cells and plots them on a canvas. These cells then evolve according to the classic rules of the game of life. The game of life illustrates how complex behaviour can arise from simple rules, a key concept in chaos theory. In this case

Fractal portal VFX idea

A while ago I was watching Chris Danforth's lecture series on chaos. During one of the lectures he showed the Julia sets, which you can play around with here. I thought that moving along the negative real axis would make a really cool portal opening effect. I made

Julia set explorer

A few weeks ago I wrote a bit about how Mandelbrot zooms are created, check that out here. Today's article is about that fractal's relatives, the Julia sets. To refresh ourselves, the Mandelbrot set is generated by asking whether zero will explode or not when you

Lake from a dream: the Fresnel effect

I made a lake in unity! You can scroll down to walk around it in your browser. The lake is achieved by combining a few different effects. Reflections, small waves on the surface (generated by layering noise at two scales that shifts in time), waves that emanate from the player

Fractals, Infinty and AI

Have you ever watched one of those super deep fractal zoom videos? I saw this one in particular back in high school and remember being blown away; how was such beauty being constructed? I thought that there must be some complicated mathematics that was being used to generate the image

Von Kármán vortex street Lattice Boltzmann method sim

A von Kármán vortex street happens when fluid flows past a cylindrical obstruction. You get a series of vortices that march down flow. I wrote a Lattice-Boltzmann method solver in c# to simulate such a scenario. It suffers from numerical instability but if the velocity is raised slowly enough, you

What's been happening? (Part 2)

This is the second of two posts in which I try to give a proper answer to "what's been happening?". I am attempting to give an overall picture of how things became the way they are. Part 1 was on prehistory and started with the big

What's been happening? (Part 1)

With these two posts I am going to try and give a good answer to the question of "what's been happening?". It can be difficult to get an overall picture of how things became the way they are. That is what these posts attempt to provide.

Rain before 7, fine by 11

You may have heard this proverb before. It's a British saying based on our changeable weather. If you live here, you probably noticed that heavy rain will often clear up by noon - or at least weaken considerably. But how true is this observation really? Grey and rainy

Starting a visual artistry journey: working with shaders

I love the way fluids move, you can probably relate to that. The beautiful swirling patterns you see when washing the dishes or those dramatic clouds over the ocean give life a bit of extra meaning. That is one of the reasons why I studied maths at university and definitely

On the political history of the Milky-Way Galaxy

This is a slightly more technical write up of the work in this blog post: Politics in the milky way. Summary Robin Hanson and colleagues recently proposed that “Grabby Aliens” could be the reason why humanity seems to have arrived cosmically early. In the Grabby alien model there is no

Liouville's equation

Summary I explain what the Liouville equation for the probability density function (PDF) is and its significance for weather prediction and chaotic systems more generally. I give its derivation, show how it is applied to a simple ODE and the Lorenz 63 system, I discuss its extension to the Fokker-Plank

My first game jam

Last month a dear friend of mine – one Stefan Colakovic - had his birthday. To celebrate we decided to try our own 24-hour game jam. Our first idea was to use it as an opportunity to learn the basics of making an online multiplayer game. After 2 hours we realised,

Making my first App

I have a long list of things I want to understand and make. Some of the entries on this list are apps. Back during the winter break I thought I would finally get the ball rolling and learn to make a simple android application. Of the apps I actually want

Beauty that computers can’t capture (for now)

Can a computer write a symphony, can a computer turn a canvas into a beautiful masterpiece? Well... yes. We have reached an era of AI art and music generation. But what can our silicon friends not do? I give 3 examples that came to mind. The first is mathematical. We

Why do waves always come towards the beach?

Have you ever noticed that the waves always come towards the shore at the beach? That's quite strange right? A storm out in the ocean will generate waves and they will travel radially outwards from the source, so how come we never get to see the waves coming

Making that one Windows wallpaper in Unity

Environments in virtual reality are amazing. Most of us have walked around cities and mountains that exist only in 1s and 0s. I have many ideas for projects I would like to complete in the future and some of those would look much better placed in a virtual world. So,

Where do people find the weather hardest to predict?

In a previous blog post I showed where the weather deviated the most from the monthly average. In this blog I am going to combine those fields to make a map of where I think a local would find the weather hard to predict. What do I mean by predicting

Automatically sending diary prompts to my mum

For Christmas I was bought The Daily Stoic Journal by my lovely mum. This provides stoic writing prompts for a diary. Things like “What is my purpose in life?” or “How can I keep my mind clear from pollution?”. I don’t consider myself a stoic but the prompts should

Where is the weather most variable?

My PhD is about the predictability of the weather. To me, predictability means the rate of ensemble spread. Ensemble spread is how quickly computer simulations starting with similar weather disagree with each other. You could also think about it as how predictable a robot would find the weather. But what

Politics in the Milky Way

What's your perfect profession? If you could pick out of every job that has existed or will exist, what would you do? I know my answer. I would be an archaeologist. That may seem odd since the profession already exists and I am in an apprenticeship to become

Snake in 3D

Use WASD to move! During dead moments in the late 2000s, think airport lobbies or bus stops, Snake on my Nokia phone would always come to the rescue. A few years ago I wondered why I had never seen a 3D version of the game, one that controlled like the

John Conway's Game of Life

Conway's game of life was born in 1970. It is hard not to come across it at one point or another. The idea is that simple rules result in unpredictable and often beautiful chaos with emergent order. You start with a grid of cells, some of which are

Metalic rainbows all around us

Have you ever looked closely at metal cutlery after sticking it into hot food? An oil slick on the road? The strange sheen on a beetle? These colours, sometimes called oil slick or neochrome, have a common origin. I wondered where the colour came from and found a couple cool

How to make a website to show WebGL creations

I spent an afternoon trying to figure out how best to make a website that I could put simulations on. Although all the steps turned out to be straightforward, the main confusion was what website platform to use that would make the process as simple as possible. With the hope

3 Body Instability Simulator

A simulation made in unity to demonstrate how the unstable nature of 3 orbiting stars leads to globular clusters having their more massive stars closer to the centre.  The music used is "Stars" by Stefan Lu. Click the cog in the top right for instructions.

Far off cannons are heard but closer ones are silent

Cannons are loud. Before an interesting discussion with Tom Mulder, a DPhil student who studies how animals detect vibrations, I imagined that the further from a cannon you were the quieter it would be. This is not true.

My first post: Coming soon, more things I find interesting

I'm Salah Kouhen, a PhD student at Oxford studying the predictability of the weather. My interests are varied and this is my place to post about anything and everything. If our interests overlap you will find some cool things here. I hope you have fun!