Kelvin-Helmholtz Instability

I recently filmed a short interview with Professor Mike Merrifield about Kelvin-Helmholtz instability.

Professor Merrifield - based in the University of Nottingham's Physics Department - nicely described the effect with pencil and paper.

My oft-collaborator Pete McPartlan later did some nifty work to "animate" this description.

But before releasing the video, we started looking at other videos which demonstrated the effect.

The first one we noticed was this, by Professor Grae Worster at Cambridge. I emailed him and he kindly gave his approval for me to use the footage if it was helpful.

But then I found another video - this one - and to my surprise it was filmed by students at the University of Nottingham. (I notice the logo on the lab coats before reading the description)

I contacted them on Facebook and they told me the apparatus still existed in the university's Faculty of Engineering  - they said I should contact Dr Barbara Turnbull.

So it was back to Nottingham for another day of filming. The result is a few videos.

This one is the main interview with Mike, now illustrated by both Pete's animations AND Dr Turnbull's demonstration.

Then a second video just showing how the experiment worked... I thought it was worth it's own extra film.

And for the real diehards, the full slow motions that can pored over in detail.

Using the Hubble Space Telescope

The latest video on Sixty Symbols features Dr Meghan Gray discussing how the Hubble Space Telescope is maneuvered.

But perhaps equally interesting is the "extra footage" posted to the nottinghamscience channel, in which Dr Gray discuses her own experiences using Hubble on the STAGES survey. The relevant section starts from 1 mins 37secs.

Here's an earlier video when Dr Gray discusses the STAGES research.

And for more on STAGES science, visit here.

Like telescopes? Try my telescope tour videos.

The Squared Square

The latest Numberphile video with James Grime discusses "squared squares".

A great source of Squared Squares info is

For a fun way to show some support for Numberphile, why not try a Nice Square T-Shirt.


Also wanted to share a bit more about this photo, which appears in the video and was used with thanks to Iain Strachan.

It shows the Trinity Mathematical Society in 1938, and the key people in the picture for the "squaring square" video are Brooks, Stone, Smith and Tutte.

Mr Strachan came across the picture via his late uncle, Frederick C. Strachan, who is also shown.

Mr Strachan shared the following family story about his uncle.

"He was a very bright mathematician - according to his school (Taunton School), the best the school ever had.  He had a free place at Trinity.  My Dad, Norman Mervyn Strachan, also got a place at Trinity to read maths, but not a free place.  Unfortunately, his parents didn't have enough money to send him, plus the war was coming soon, so Dad joined the Home Guard, and eventually became a Captain in the Royal Corps of Signals. 

"Freddie also became an officer in the Royal Corps of Signals (1st Lieutenant).  A favourite story in the family was when he was interviewed by a Colonel, initially for the Royal Artillery.  The Colonel looked at his application and said 'Hmm I see you have a double First Class Honours degree in mathematics from Cambridge'.  'Yes' says Freddie.  The Colonel replies '... I suppose that would include trigonometry?'

"That story got repeated at Freddie's funeral (he died at the age of 94).

"I am somewhat surprised Freddie didn't get recruited by the GCCS to Bletchley Park, like Tutte - he was also a whizz at crosswords.  But he graduated in 1938 and got a job as a patent examiner before the war started, and continued in that career afterwards."

The Complete Collection of Incompleteness

Gödel's Incompleteness Theorem has been one of the most requested videos on Numberphile.

The task of explaining it was taken up by none other than Professor Marcus Du Sautoy (a household name in the UK, at least when it comes to mathematics!)

We posted three videos - a main explanation plus two lots of "extra footage" .


Professor du Sautoy covers the topic in his latest book too.

In the US it is called The Great Unknown -

In the UK it is called What We Cannot Know -

More of the professor's books:

Neil wins President's Prize

Anyone who watched Periodic Videos will know the importance (and cult hero status) of Neil Barnes.

Neil is a senior technician in the School of Chemistry at the University of Nottingham.

Since we started making videos, Neil has been the guy who sets up, carries out and cleans up most of the experiments.

But what you do not see on camera is that Neil is also a key part of coming up with ideas and planning the whole process.

When I'm not around, Neil spends many hours plotting future videos, dreaming up new experiments, and building devices to make them possible.

This week Neil was recognised for his role with the Royal Society of Chemistry President's Award.

Professor Sir John Holman, president of the Royal Society of Chemistry, said: “Neil brings together two things that are very important to me personally... 

"The first is technical skills. Skilled technicians are vital for the success of the chemical sciences and Neil has shown their importance as a research technician in physical chemistry at the University of Nottingham.

"The second is outreach: as chemists we all need to do our bit to inspire the next generation of chemical scientists, and Neil has helped bring the excitement of chemistry to thousands of young people around the world by supporting Sir Martyn Poliakoff so expertly with his brilliant Periodic Videos.

“For me it feels just right to be presenting this award to Neil Barnes who has brought these two priorities together so fittingly.”

Jonathan Hirst, Head of the School of Chemistry, said: “Our technical staff are the cornerstone of much of the School’s activity. Neil has supported and inspired many students and colleagues in the School, and much more widely through social media.”

Professor Poliakoff said: “Neil is a key person in the success of our videos.  His enthusiasm, knowledge of chemistry and silent acting skills have made him a super-hero of chemistry.  He is an excellent ambassador for chemistry, for Nottingham and for the role of University Technicians.  And he is fun to work with!”

Pictures courtesy of

The Maestro

Alan Stewart - or "The Maestro" as I like to call him - has released a new album of piano music.

 Hanging out with Alan

Hanging out with Alan

Alan is an England-based physics teacher, but also a talented musician who has helped with my videos for many years. See some examples below.

(He's also the creator of Hello Internet's short "theme tune" that plays at the start of every episode)

The new album is called Sunsettlement - and Alan has posted it to YouTube.

But I'd also really encourage you to consider it on Spotify, Apple Music, iTunes, GooglePlay, Amazon, et al.

It's well worth your time - but also a great way to show some support for a great guy.

I listened to the whole album (twice) on a recent long-haul flight, and loved it.

To remind you of my work with Alan, here are some videos he contributed to:

And here's an interview video I did with Alan a while back...

Those links for Alan's new music: Spotify, Apple Music, iTunes, GooglePlay, Amazon.