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.

Measuring the temperature - Physics Stop

Feb 22, 2019

I’ve just bought some thermometers, to use with a first-year physics class. A box of ten of them. Alcohol filled, which makes them a whole lot safer than the mercury ones. (If you have a mercury thermometer, my advice is never, ever break it, especially if it’s at home. I broke one at university a few years ago – at least we had the ability to clean it up properly – but most homes won’t.) Anyway, a little test as to how good they are. What is the temperature in my office? They are graduated in whole degrees Celsius, but I reckon I can read them to the nearest half a degree. Here are the readings (in degrees C), after they have all been sitting next to each other on my desk for a while: 24.5, 25.5, 25.0, 24.0, 24.0, … Read More

Alice the camel - Unsorted

Feb 05, 2019

As we drove on a family outing at the weekend, we sung “Alice the camel”.   For those who don’t know it, it goes like this (to the tune of “Dem Bones”): “Alice the camel had five humps; Alice the camel had five humps; Alice the camel had five humps; so go, Alice go! Alice the camel had four humps… Alice the camel had three humps… Alice the camel had two humps… Alice the camel had one hump… Alice the camel had no humps; Alice the camel had no humps; Alice the camel had no humps; so Alice is a horse (of course!)” Only when you have a gifted six-year-old in the backseat, it doesn’t stop there: “Alice the camel had minus one humps… And we got up (or should that be down?) to about minus nineteen humps before the song … Read More

Why you shouldn’t eat beef - Physics Stop

Jan 11, 2019

“Don’t eat beef.” Such a statement does not go down well in New Zealand,  especially in Waikato, where the cow reigns supreme. I don’t say it as someone who wants to peddle a “Meat is Murder” message. I don’t believe that at all. I say it as someone who wants New Zealand to take Climate Change seriously. Quite simply, producing a serving of beef produces a staggering amount of carbon dioxide, as the diagram here from Poore and Nemecek (2018) demonstrates: [Source:  ; original data from: Poore, J. and Nemecek, T. (2018). Reducing food’s environmental impacts through producers and consumers. Science 360, 987-992. DOI: 10.1126/science.aaq0216  ]This might need to be put into more context.  Driving 100 km in my car produces something around 14 kg of carbon dioxide.  One serving of high-impact beef tops this. Even a low impact serving of … Read More

In praise of fixable appliances - Physics Stop

Dec 17, 2018

Last week saw the first ‘fault’ on our washing machine. We’ve had this particular one for nine months, and with a baby and young boy in the house it is well used. When I went into the laundry to empty the machine I found the cycle had not finished as I had expected. Instead, the machine was flashing an error code at me. You know the ones. The kind that laugh at you and say “Ha! You’ve overworked me.  I’m on strike. You’re going to need to get someone in to look at me. It’s going to be pricey. And just before Christmas too; in fact, you might have to wait till the New Year before I’m back working again. Oh, and don’t get any ideas about being able to open my door and recovering your clothes – I’m locking … Read More

Colour blindness and Bayes’ theorem - Physics Stop

Dec 13, 2018

Following from my last post, there’s more to say about colour blindness in my family. This time we’ll look at my side of the family.  My maternal grandfather was red-green colour blind. That means my mother is a carrier of red-green colour blindness, with a “faulty” (well, “alternative” would be better) X-chromosome.  And as a male, it meant I had a 50:50 chance of being red-green colour blind, as I have only one ‘X’, inherited from Mum. As it turns out, I got the non-alternative version, and so see colours “normally”. But what about my two sisters? They both have one ‘X’ inherited from Mum, and one from Dad. But which of Mum’s X-chromosomes did they get? Since Dad wasn’t red-green colour blind, we know they would have got a normal version from him, and so, if one or … Read More

Colour vision - Physics Stop

Dec 10, 2018

We’ve known for a while that child number 1 (male) is red-green colour blind. This comes as no surprise – with his maternal grandfather being the same. The genes responsible lurk on the X-chromosome. That means his mother is a carrier of red-green colour blindness, and child number 1 had a 50:50 chance of picking up her faulty X-chromosome.  It also means that child number 2 (also male) has a 50:50 chance too, though it’s too early to tell whether he is the same. For the most part, the colour blindness is of negligible consequence. Sometimes it creates some amusement and puzzlement – such as when he asks for the “green one” when there simply isn’t a green one there.  Sometimes it’s intriguing, though.  He clearly sees colours in a different way to me and appears to be able to distinguish … Read More

Hydrophobic cabbage - Physics Stop

Nov 26, 2018

Saturday afternoon saw a break in the rain, and I was able to get out into the garden. The first thing I did was to harvest a red cabbage for dinner. The nice bit of the cabbage is the tightly rolled leaves in the middle, but surrounding that are a whole lot of larger leaves, which I removed and left for the chickens. After another long period of rain, I returned and found the leaves on the lawn filled with water. That wasn’t surprising. However, the water ‘sat’ in the leaves in a rather unusual way. The leaves are very hydrophobic – meaning water doesn’t stick to them. There were no droplets of water on the leaf – they had all run down into a ‘pond’ at the leaf bottom, leaving the edge of the leaf completely dry. The water … Read More

Biological variability and Pakistani batting collapses - Physics Stop

Nov 21, 2018

So, yesterday we had our Science Communication students looking at social media and blogging in particular. Alison Campbell and I talked through what makes a good science blog, and the students got to explore and look for themselves*.  In the coming week, the students need to put up a blog entry themselves. (I’m afraid these will be private to the paper, though we might persuade the authors to release the best of them more widely.) As we talked with the students about blogging, a repeated question was “how do I choose a topic?”  I think the same advice applies to blogging as it does to writing in general: “Write about what you know.”  So, I ask the students what they are majoring in. What topics in their studies have really got them saying “Ooo, that’s interesting”? What do … Read More

Cell phones give you cancer. Yeah, right. - Physics Stop

Nov 15, 2018

It’s been a couple of weeks since the NIH studies on mice, rats and cellphones hit the headlines.  The studies were released with perfect timing to be used in our Science Communication paper – a third-year level paper for science undergraduates on communicating science ideas well. In short, we had half the class look at what mainstream media said about the study (notably this NZ Herald article),  half the class look at what the Science Media Centre released on it, and then, finally, what the original sources for the mouse studies and the rat studies said. I asked the class in small groups to pull out the key messages from the commentary that they were looking at. What we got was: Mainstream media (NZ): Cell phones give you cancer; if you are male then don’t keep a … Read More

The difference between an engineer and a physicist - Physics Stop

Oct 20, 2018

As a researcher who has recently published an article in the elegantly-named journal ‘Biomedical Physics and Engineering Express’ (in other words, biology, medicine, physics, engineering all in one) it’s clear to me that the boundaries that we often like to use to define ourselves are rather blurry. I am a physicist (yes!) but also, at times, I have to drift into being an engineer, biologist, mathematician, computer scientist and so forth. Indeed, many of humanity’s best scientific advances have been made at the fringes of disciplines, where different scientists have come together with different perspectives on the same problem and come up with something wonderful as a consequence. That said, I shall now have a moan about a piece of software (no names mentioned) that has clearly been written by engineers not physicists. You don’t need to understand what my … Read More