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.

More strange quantum stuff - Physics Stop

Sep 21, 2018

I have talked about some of the strange quantum mechanics effects before. An example is the two-slit experiment. If we fire photons (particles of light) at a pair of slits, and then measure where they appear on the other side of the slits, we get a two-slit diffraction pattern – exactly what we’d get if the photon travelled as a wave.  We can conclude from that that the photon has travelled through BOTH slits – not one or the other – since if it went through just one it would give a different diffraction pattern.  But now if we try to measure which slit it went through (by putting a detector just by one of the slits) we do indeed see that it goes through one or the other – but what is more, the pattern we get … Read More

Relative Velocity - Physics Stop

Sep 20, 2018

Those of us who fly out of New Zealand reasonably frequently will have noticed how flight times differ significantly depending on whether one is travelling west to east or east to west. Take my recent flight to and from Perth, in Western Australia.  The Auckland to Perth flight was timetabled to last 7 hours 25 minutes, while the return flight was timetabled for just 6 hours 10 minutes – 17% less time than the outward flight. The actual time in the air is (usually) less than this, with the timetabling including all the stuff that happens on the ground when the doors have been closed. (What are they doing in this time, I sometimes wonder…) Now, for my recent flights, the flight times were very telling. The outward flight time (the time in the air) was actually 7 hours 30 … Read More

The problem with undergraduate textbooks… - Physics Stop

Aug 07, 2018

In the last few weeks I’ve been talking with a colleague about magnetizable materials – what they do and how they are categorized. I’m talking about things such as iron – which, when you put them in a magnetic field, will magnetize. That makes the field bigger than you started with. Some materials will stay magnetized when you take them out of the external magnetic field (these are called ‘hard’ materials – nothing to do with their physical toughness), and some won’t (or will only weakly – these are called ‘soft’ materials). One of the properties that characterizes a magnetic material is the ‘relative permeability’ – often given the Greek letter ‘mu’ with a suffix ‘r’ for ‘relative’.  It tells us (sort of) how much a magnetic field will boost by, compared to air,  if you use a magnetic material … Read More

Expensoheat - Physics Stop

Jul 16, 2018

We have now been in our ‘new’ house for four months. This one still does feel a little ‘new’, being only 5 years old. It even incorporates some radical features (for New Zealand): proper insulation, double glazing (though I note that the frames are still aluminium) and well-engineered drainage from what otherwise would be a swamp. The house came with some built-in heating.  A heatpump does the main living area (very nicely) but there is also a gas fire in the separate lounge. The gas fire is hopelessly overspec-ed – turn it up full and it’s capable of turning the lounge into an oven even on the coldest day. But now that we’ve worked out the remote control on it and can set it to a particular temperature, it does a lovely job.  [Gas fire, gas hot water heating – … Read More

Back to the blog - Physics Stop

Jul 02, 2018

Having had a rather extended half-time break from blogging I have some time to get it kicked-off again. And what better topic that the Football World Cup.  (Or, as it’s referred to everywhere except New Zealand, the World Cup.)   There are some great examples and analogies of physics that we can pull from this, but I thought I’d start with the Video Assistant Referee (VAR). Generally speaking, I approve of the use of technology-based refereeing aids in professional sport. Since everyone watching on television has almost instant access to close-up replays from all angles, it seems crazy that the referee can’t have a second look at something. So long as it doesn’t interrupt the game too much. I think it’s worked pretty well here, though it does seem that the penalty count is getting rather extreme. How long will it … Read More

Astigmatism and Amazing lenses - Physics Stop

Jul 25, 2017

There is no denying it. I am middle-aged. The latest evidence is the progressive-lens glasses. I had tried to put off getting these for as long as possible (warning to you younger readers — they are not cheap!) but it was just getting too difficult without them. We pretty-well take for granted good vision, but most of us can only enjoy really good vision by virtue of really good lens-making methods. In my case, while my vision was fine while at school, it became apparent rather quickly at university that mine wasn’t as good as some of my friends. Sat at the back of one of the large lecture theatres I really couldn’t kid myself that I had good eyesight. I couldn’t read what was on the screen at the front, while others around me could. While my vision isn’t so … Read More

Sycamore seeds and wind turbines - Physics Stop

Jul 18, 2017

At the recent NZ Institute of Physics conference in Dunedin we heard about a wide range of different physics topics -measuring electrical forces; atomic frequency combs; why a highly gendered physics class is not a good thing and measuring forces with your phone. One very simple but thought-provoking presentation was by Tim Molteno — on sycamore seeds and their properties as little wind turbines. As far as I understood it, Tim’s work here was a follow-up to what his son Linus had done as a science fair project. Sycamore Seeds If, like me, you grew up amongst deciduous woodland, you’d have enjoyed playing with sycamore seed helicopters. They can fall very slowly indeed, giving the seed chance to drift in the wind away from its parent tree and get some chance of seeing some daylight when it germinates. It’s pretty … Read More

Improving gender balance in physics - Physics Stop

Apr 07, 2017

The Institute of Physics has just released a report on recent interventions designed to improve the uptake of physics at ‘A’-level by girls*. Although there have been considerable efforts in the UK to improve the gender balance over two decades, there has not been any substantial change – about 20% of a typical A-level physics class is female. Why is this? In the latest study, three different methods were trialled. While they all had modest impact on their own, a much greater effect was observed when all three methods were used together. You can read the details in the report, but briefly, the three approaches were as follows: 1. Developing girls’ confidence and resilience. Previous research had found that boys often consider their own successes as being down to their own hard work and skill, … Read More

Bell ringing: inertia and resonance - Physics Stop

Apr 05, 2017

Only a week more to go in Perth. Time here has gone so quickly. It’s then off to UK for Easter to see my family before returning to Waikato. On Saturday we had a tour of the bell tower on the waterfront. It’s a great looking structure (in my opinion) – and houses the original peal of bells cast for St Martin-in-the-Fields in London. Swan Bells, Perth, Western Australia. Wikimedia / SeanMack. Just how they came to Perth is a bit of a long story, but they had to be removed from St Martin’s because they were too heavy and were causing serious structural damage to the tower. Now they have a new home, along with a great many other bells. Collectively they are called ‘The Swan Bells’ – in Perth naming something is easy – … Read More

The indeterminate cheese flake - Physics Stop

Mar 30, 2017

A couple of days ago I arrived ‘home’ to discover our local ant colony at work. There’s a nest located somewhere in the bushes at the front of our temporary home, and the occupants have become rather adept at raiding our kitchen. Anything left on the kitchen bench is fair game for the taking. Ants are amazingly strong for their size – any little bit of food like a small oat flake gets picked up and transported back to the nest. Now, in this case the ants were after the grated cheese. Some sizeable flakes had been left on the bench and these were going to be a feast for an ant colony. By sizeable I mean something you get from a coarse grater – perhaps 3 mm wide and maybe 2 cm long. Now, to get them off … Read More