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.

Static hair - Physics Stop

Oct 15, 2018

It’s one of those annoying laws of nature that the times you want to do a demonstration of static electricity with a Van der Graaf generator are the times when the atmosphere is least suited to it. Damp conditions equal a damp demonstration. But yesterday was really good. No Van der Graaf generator needed – just a ten-month-old on a trampoline. A bit of crawling around and it really was a bad hair day for the bubba. Apologies for the cropped, slightly out-of-focus cellphone photo. Keeping the subject still was a bit problematic.  The very fine hair will be playing a part in this photo – not much charge is needed to separate out those strands. Needless to say, we both were ‘shocked’ when I lifted him off the trampoline. The post Static hair appeared first on … Read More

Fuel consumption: fewer vehicles means less than fewer emissions - Physics Stop

Oct 11, 2018

So, school holidays are coming to an end.  My son is breathing a big sigh of dismay. And, like so many other commuters, so am I. I’ve enjoyed two weeks of being able to get to and from work (especially the ‘to’) without traffic hold ups and ‘having to go the long way around’.  My 23 km commute from Cambridge to Hamilton goes from about 32 minutes average to about 23. (I hear many of you Aucklanders or Wellingtonians saying …”32 minutes: is that all?…”) The point I want to make is about fuel consumption. My Toyata Yaris is pretty economical as petrol cars go. It’s got a fuel consumption gauge on it – I reset it everytime I fill up and it tells me the average litres per 100 km I’ve done since I last reset it. During school … Read More

New Zealand: It’s time to up our game on disability - Physics Stop

Sep 28, 2018

I read with delight the announcement that the NZ government will now relook at how it funds those who care for family members with disability, and repeal section 4A of the NZ Public Health and Disability Act. That is a big step in the right direction. But it does need to be put into a broader context: when it comes to disability issues, New Zealand is waaaayyyyyyy behind the game. In the last few years I have learned from a disabled friend that NZ legislation on disability is patchy and (like section 4A) discriminatory, not fit for purpose, and, to a great extent, ignored. Individuals, organizations, and even the government alike routinely flout what positive legislation does exist with few sanctions or prosecutions. Societal attitude in New Zealand is that disability is “someone-else’s problem.”  It is not. I will … Read More

Sucking up Spaghetti - Physics Stop

Sep 26, 2018

No. I’m not talking about 6-year-old boys sticking one end in their mouth and sucking.  I’m talking about vacuuming-up old bits of uncooked spaghetti on the kitchen floor. So, on taking the vacuum cleaner over the kitchen floor at the weekend, I could see that there were a few broken strands of uncooked spaghetti to clean up, along with the usual dust and bits of cereal and apple pips and who-knows-what-else? But this is what was puzzling. While the vacuum cleaner had no problem with the dust and bits of cereal and apple pips and who-knows-what-else, it struggled with the spaghetti. It just wouldn’t suck them up, even if I carefully placed the nozzle over the spaghetti. I thought to start with that this was just because the pieces were too long and not getting through the opening of the … Read More

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