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.

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

Tanker physics - Physics Stop

Oct 14, 2015

I’m currently at the Metrology Society of Australasia conference in beautiful Queenstown. For those that don’t know, which might be most of you, metrology is the science of measurement. How do you measure things well? At this conference, we’ve got presentations on measuring temperature, pressure, liquid volume (a surprisingly tricky one this – if you want to do it accurately, quickly and non-destructively), electrical properties, so on and so forth. There’s lots of industry engagement here – unsurprising since making measurements well can make real differences in a company’s bottom line. For example, Richard Suckling from Fonterra talked this morning about some of the problems that Fonterra faces in terms of collecting milk from farms, and the measurement technology that is packed into each milk tanker. Milk tanker routing is a real example of a ‘travelling salesman problem’ – how … Read More

Plants in circular motion - Physics Stop

Oct 05, 2015

In our first-year physics lab we have the following horticultural experiment.  Here we have some bulbs growing on a rotating turntable. The array of five pots is placed on the turntable so that the centre pot is at the centre of the turntable; the left- and right-hand pots are at the perimeter.The turntable is rotating at about half-a-revolution a second. What happens as the plants grow? Actually, this is a demonstration of centrifugal force just as much as it is a horticultural experiment. First the biology bit. Plants grow, pretty-much, towards the light. I’m sure someone will tell me the mechanism by which this happens, but for now I’ll just state that as true. In this case, however, what is towards the light is constantly changing. The plants get equally illuminated from all sides. So we can take light out … Read More

If gravity increased… - Physics Stop

Sep 25, 2015

A colleague remarked to me yesterday, as we were trudging up the two flights of stairs from the tea-room to the third floor, “I’m sure they turn up the force of gravity in this building each year.” I feel like that too, sometimes. However, I suspect it has more to do with the aging process that any changes in physical constants. But…what if…? What would life be like if gravity were say, double what it is now. How different would life be? There are many ways of tackling that question. So I’ll phrase it in this way. Imagine that there’s another universe in which a similar-sized and atmosphered Earth exists, but where the force of gravity is double what it is in this universe. What might life look like on that Earth? First, I need to say that the ‘Earth’ … Read More

Clothes racks are not the reason for mouldy homes - Physics Stop

Sep 21, 2015

I read the ‘Rental Nightmare‘ article on last night. Some of the stories are horrific indeed, and I’m reasonably confident that the writer has deliberately sought out the worst situations rather than the most common situations. But one cannot deny that a great deal of housing in New Zealand is sub-standard. In housing-deficient Auckland, in particular, families are forced into cold, damp homes because there is nowhere else they can afford.  I’ve been in NZ eleven years now, and I have still to wrap my head around why this is. It seems that up to the 1970’s, houses were designed with three underlying assumptions: 1. New Zealand has a warm climate, 2. New Zealand has a dry climate, 3. Everyone needs a large, detached house. While the first is arguably true for parts of the country for … Read More

Axis labels – accurate but not at all obvious - Physics Stop

Sep 14, 2015

I had a conversation with a class this morning regarding the labelling of axes on graphs.In particular, how we should indicate the units. Most quantities we deal with in physics carry units. A speed might be 35 km/h, a distance might be 16.8 mm, a pressure could be 28 kPa. Saying that a speed is 35 is wrong and meaningless. 35 km/h is rather different to 35 m/s or 35 inches/day.  If we are plotting two quantities, for example to find a relationship between them, we need to indicate what units the axes are in. A typical way to do that would be to include the unit in brackets after the label. So if we are plotting a distance, we might label our axis ‘distance (m)’, with the ‘(m)’ indicating that the numbers on the plot are in … Read More