# 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.

## Blue sky - Physics Stop

Aug 31, 2009

I'm still working on the problem of why is the sky blue?  Now, I've already told you its because the short-wavelength blue light is scattered more than the long-wavelength red light, but why are short wavelengths scattered more than longer ones? In words suitable for a blog.

I could do some maths to show you that's the case, but that's really a cop-out. (Plus most of you wouldn't follow it.) I think if a physicist has to resort to maths to explain something, it means he doesn't understand it himself. (That said, you will struggle to do physics without being reasonably competent at maths - since maths provides the language in which physics is often best expressed.)

Help!

## The scientific method - Physics Stop

Aug 28, 2009

This morning we had a school group visit us from Whakatane - about 30 year 10 students (14 and 15 year olds) - they carried out some activities in Chemistry, Earth Sciences and Physics. I led them (as two groups) in a physics activity involving catapults.

After doing the boring bit (talking about how energy is transferred from one form to another as the catapult is loaded and fired) we got to actually using the things. Our catapults have a metal arm, that can be bent back and locked in place. A projectile is placed on the arm, and then the arm is released. As it springs back into position, it throws the projectile about fifteen metres (if you get it right) across the room. Students can vary the release angle of the catapult, the mass of the projectile they put on it, and the effective length of the spring arm. They need to think through the best combination to get the projectile going the desired length.

## Landing gear failure - Physics Stop

Aug 27, 2009

Last night our cat failed to live up to the reputation of his species for executing four-footed landings when he lept off a perch in hot pursuit of a piece of string, landed on his front paws with too much forward rotation, performed a graceful flick-flack and thuded head first into the CD rack. After a couple of seconds looking very dazed he got to his feet again and decided (to our relief) he was still fit enough to teach that bit of string a lesson.

## What’s happening in Geneva? - Physics Stop

Aug 26, 2009

In the last few days I've had a couple of people ask what is happening with the Large Hadron Collider.

Well, if you want the latest news, you can grab the press releases from http://lhc.web.cern.ch/lhc/News.htm . In short, they are doing various tests, and finding and addressing various problems as they arise. It now looks like November before the collider is 'fired-up', (press release 16 July 2009) but initially it will only be running at a paltry 3.5 TeV energy (that's still a pretty mean machine) while the technicians gain practice with running it - it looks unlikely they'll take it up to its full 7 TeV until 2011 (press release 6 August 2009).

You'll see it hit the popular news again, I'm sure, as November approaches.