Marcus Wilson

Dr Marcus Wilson is a lecturer in the Engineering Department at Waikato University and author of the Physics Stop blog. His current research involves modelling of the electrical behaviour of the human brain during natural sleep, focussing particularly on the transitions between sleep states. Previous research interests include infra-red physics and signature control (stealth) and quantum Monte Carlo methods. He graduated from Cambridge University in 1992 (BA Hons) and completed his PhD at Bristol University in 1995.

Weighing magnetic properties - Physics Stop

Jan 12, 2016

It’s a New Year and there are lots of things to do at work before the students get back in any numbers. There are still summer students and research students here, and in the last couple of days I’ve been working with a summer student on getting a new piece of equipment running for our Experimental Physics paper – the Gouy Balance for measuring magnetic susceptibility. Schematic of the Gouy Balance. Source: Wikimedia Magnetic susceptibility is a measure of how magnetically responsive a material is – how much it magnetizes when placed in a magnetic field. Materials can be categorized as diamagnetic, paramagnetic or ferromagnetic. Paramagnetism describes a material that magnetizes with the applied magnetic field – that is, it will be attracted to a region of high magnetic field. A ferromagnetic material goes beyond this … Read More

Tip or slide? - Physics Stop

Dec 18, 2015

We had our departmental Christmas lunch on Tuesday, outside in the campus grounds. We had some lovely sunshine, but the wind did rather spoil things. I’ve certainly got used now to living in a very wind-free place – a fresh breeze is something quite unsual here. We were hanging on to our paper plates, but didn’t expect to have to hang on to glass drink bottles as well. One particular gust was strong enough to take a newly opened individual-serving-sized glass bottle of lemonade and blow it over.  So, being a physicist I had a go at estimating just how strong the gust of wind needed to be to push over a lemonade bottle. As the wind hits the bottle it has to change direction, and this causes a change in its momentum. To do that requires a … Read More

On the track at the Avantidrome - Physics Stop

Dec 14, 2015

Yesterday I finally managed to achieve one of the things on my ‘to do’ list that’s been sitting there for about a year – attend a ‘Have a Go’ session at the velodrome in Cambridge. For those that don’t know it, it’s New Zealand’s new (which means about two years old) world-class velodrome and now ‘home’ to New Zealand cycling. It’s an impressive building – probably more so from the inside than the outside. Walking into the central area the first thing that greets you is a terrifying view of the banking on the corners. We were told it’s 43.5 degrees. It’s the kind of slope you’d find on a steep slide in a playground. And we’re meant to cycle on it. But our instructor built us up gradually to this. First off, was just getting used to … Read More

Is dark matter really dark? - Physics Stop

Dec 07, 2015

What is dark matter, or is there no such thing? Last week I attended a seminar by Ian Hawthorn of our Maths Department. He talked about some work which he’d done with a couple of students, Matt Ussher and William Crump. The title is a bit of a mouthful “The physics of sp(2,R)”  (what does that mean?) and I have to say that I didn’t follow most of it. But I did follow some of what Ian said, some of the time, in some places. Before I comment on what Ian said, first I need to say what dark matter is. Actually, that’s quite hard, because we really don’t know. It’s matter that we think is in the universe, but we can’t see. Why do we think it’s there? We can observe the structure of galaxies, and how … Read More

And the Nobel Prize in physics goes to… - Physics Stop

Nov 27, 2015

…the United States of America, of course. Hamish Johnston, editor of, has put together a neat little piece looking at where Nobel physics laureates start and end their days. There’s no surprise on the net migration front – a huge flow from everywhere to the US. What Johnston’s graphic doesn’t indicate is when the award winner migrated (e.g. was it before or after their prize?) and multiple migrations – he just shows where they were born, and where they died or are currently living. The biggest ‘loser’ is Germany – in fact a whopping 13 German-born laureates left Germany (11 of them for the US, including Albert Einstein, and 2 to Switzerland) although World War II accounted for many of the migrations here. While 30 laureates have immigrated to the US, only 2 have emigrated including the … Read More

Gender stereotyping and physics - Physics Stop

Nov 20, 2015

The Institute of Physics (IOP) has recently released “Opening Doors: A guide to good practice in countering gender stereotyping in schools” (You can access the report here and read some commentary at a recent IOP conference here.) Although funded jointly by the Government Equalities Office (now I’m sure such a thing didn’t exist when I lived in the UK) and the IOP, the study is not confined to physics, nor even to science. However, given the gender imbalance in physics, the IOP has a strong interest in this. Also, given the low numbers of students studying physics at Waikato, it is something I have a strong interest in too. The report covers many areas, such as careers guidance, staff training, tackling sexist language (whether it be conscious or unconscious), use of statistical data, and so forth. Read More

Feedback, feedback and more feedback - Physics Stop

Nov 13, 2015

I’ve recently received the final report from the Conference Organizing company that looked after the New Zealand Institute of Physics (NZIP) conference, back in July. The report includes such things as the final accounts, the breakdown of who attended, and feedback from participants. It’s the feedback that is particularly interesting.  When we attend an event, it’s usual to find a piece of paper thrust in front of us before we leave, asking for feedback. Nowadays, it’s often an electronic form that comes to your inbox. And it’s easy to ignore it. However, what we write is really valuable to the event organizer. How are they going to know what went well and what didn’t go  well, unless people tell them? If something needs changing, the organizer needs to know about it. Likewise, if something was really … Read More

Attacked by an umbrella - Physics Stop

Nov 05, 2015

We have a spring-loaded umbrella at home. The idea is that you press a button, and it automatically springs into shape – its shaft springs out and the canopy unfolds. I’ve often wondered about the wisdom of such a mechanism and thought what would happen if it went off in an inconvenient confined space, such as a shop packed with expensive china ornaments.To reset, after use, you press the button again to fold up the canopy, but then need to reset the spring mechanism by pushing half the shaft inside the other half. It’s that resetting bit that got me yesterday morning. On coming back inside the house after tending to the chickens I tried to collapse and reset the umbrella, but didn’t push the shaft hard enough for the mechanism to engage. Instead, when I let it go, … Read More

Global Positioning Stupidity - Physics Stop

Oct 22, 2015

I take back what I said last week about amazing vehicle management systems on milk tankers. Last night a GPS took a forty-two tonne tanker onto the three-tonne-rated Cambridge High Level Bridge, in what could have been a catastrophe. The bridge, with which I am very familiar, was designed for people, horses-and-carts, and the occasional small mob of sheep or a few head of cattle. Out of necessisty (witness the traffic mayhem this morning)  it now takes cars. NO trailers, and absolutely NO trucks. It’s not as if it’s difficult to see the warning signs – the approach is designed to slow you right down before you get onto the bridge. But then, if the GPS tells you to go that way, what are a few large, conspicuous warnings on a narrow 117 year-old bridge … Read More

How do you measure the volume of beer in your bottle? - Physics Stop

Oct 22, 2015

Someone has to do it. There are laws in NZ pertaining to how the stated  volume of bottled liquids corresponds to their actual volume.   If, for example, you are selling beer in 375 ml capacity bottles, you need to make sure that your bottling plant is working to the NZ definition of what 375 ml actually means. In a bottling plant, the volume of liquid supplied to a bottle is often controlled by back-pressure. This is the same mechanism that causes a petrol-pump to cut-out when your tank is full. Generally speaking, it gives an adequate measure of when your bottle is filled with the appropriate amout of liquid. There will always be variations in the amount supplied. One bottle will never contain exactly the same amount as the next. So for trading purposes, 375 ml must have an … Read More