About me

For my professional website, with information about my research, publications and teaching, see www.sites.google.com/site/rmlevans.

Friday, 27 January 2012

How the Aurora Borealis Saved the Civilized World

Don’t give up just yet. There is still hope for humanity. If you thought Mankind had descended into a baying horde of tax-dodging, Edexcel-colluding, The-Only-Way-Is-Essex-watching looters, bankers and phone-hackers, think again. Through the gloom shines a ray of hope that is green and fuzzy and arriving from the most unexpected direction.

It all began last week with a CME - a "coronal mass ejection". A massive solar storm flung an enormous lump of material out of the sun and into space, hurtling towards Earth at around a million miles per hour. This kind of event has long been expected, because the Sun gets restless every 11 years, and is due to do so again this year and next. In fact, the harbingers of doom have been wringing their hands in glee at the calamity promised by a large CME. When it hits the Earth, it threatens to overload power grids and burn out the electronic technology on which we have become so reliant.

On Sunday, after travelling through space for three days, the dreadful lump of solar plasma finally arrived but, guess what, civilization did not end. There was no calamity. In fact, it turned out to be a thing of beauty.

As anticipated, the myriad electrons and protons, arriving from the Sun, spiraled round and round the magnetic field lines that extend out of the Earth’s poles like iron filings on a bar magnet. And, as anticipated, the planet’s magnetic field flexed and wobbled under the assault, making it sweep past power lines, creating a makeshift dynamo. Electrical current surged through the grid but the four horsemen of the apocalypse failed to show up. The electrical surges were relatively small, and the marvellous people in charge of the world’s power supplies coped admirably.

So, did those subatomic particles from space go unnoticed by the general population? Not at all. Never has a solar flare caused such commotion here on Earth. Our magnetic field funnelled the swarm of high-energy particles toward the poles, where they smashed into the upper atmosphere, making its oxygen atoms shine with an unearthly green light: the aurora. It’s not uncommon for polar explorers and reindeer to see the northern and southern lights, but this week’s aurora were big - so big that they extended down all the way to parts of the UK, and mainland Europe.

But who cares about the aurora borealis? You and I do, but we’re special, aren’t we. For one thing, we love to marvel at the wonders of nature. Looking out into the clear night sky, and taking in the unbelievably vast majesty of it all gives us an overwhelming sense of exhilaration, that would only be increased by the excitement of witnessing the aurora. More than this, unlike the hoi polloi, we thoughtful types appreciate real beauty wherever it appears. Well...

Anyone tweeting during the last week knows that you and I are not alone in caring about the wonderful, mysterious, beautiful workings of the universe. On Sunday, and again on Tuesday when a second CME hit the Earth, Twitter was abuzz with excitement - not over the threatened electrical disaster - but over the impending aurora. People were re-tweeting the latest space weather predictions and everyone was hoping the lights would reach their local sky. First we got jealous of the Scandinavian tweeters, then Shetlanders reported miraculous skies, and soon even the coast of county Durham was alight. And across the world, we shared their joy and excitement. A surprising number of sky-watchers are expert photographers, who managed to capture some of the celestial awesomeness, even in the challenging low-light conditions, and they very swiftly uploaded their wonderful pictures for the rest of us to marvel at. Thank you aurora watchers, for sharing your anticipation, your excitement and your amazing pictures. You have restored my faith in humanity.

In the end, the dancing green light shone on many happy appreciative people, but didn’t quite reach my Yorkshire sky. I missed the live show, but I witnessed something equally beautiful and unexpected, on a social networking site.

Sunday, 22 January 2012

The reliable musings of a Physics Bloke

Welcome to my blog. Come in, put your feet up and allow me to share with you some thoughts, anecdotes and news about my lifelong vocation. I am a fully qualified Physics Bloke, in possession of one PhD and one Y chromosome. My only goal, as we mull over the mysteries of this strange universe, is to be interesting. If it’s interesting, it goes in the blog, whether it’s the latest discovery, or was know by Aristotle. Of course, being interesting is easy if you make things up (consult the red-top newspaper of your choice) but, like any scientist, I promise to pursue only the truth. OK, so that’s two goals: to be interesting and accurate, and if I witter any longer, I’ll miss the first one. So have a look at this intriguing picture.

A living superfluid

In this week’s PANDA meeting (that’s Pattern Formation, Nonlinear Dynamics and Applications) at Leeds University’s Department of Applied Mathematics, Dr Suzanne Fielding, a physicist from Durham University, presented the results of her theoretical research on "active fluids". The strange texture of folds and swirls, pictured above, is predicted by her mathematical model.

The symmetry-based theories of condensed matter physics are usually used to model inanimate materials like semiconductors, liquid crystals and magnets. But Fielding has applied them to understand the swarming behaviour of microscopic swimmers such as amoebae. These organisms are so numerous and tiny that, en masse, they form a fluid with liquid-crystalline properties, making shades of light and dark in polarized light (see picture), like a liquid crystal display (LCD).

This active fluid of living organisms flows in peculiar ways. A fluid’s viscosity is a measure of how “thick” it is – how hard you have to push to make it flow at a given rate. So water has a low viscosity, but treacle’s viscosity is high. Fielding has used her model to calculate the viscosity of a dense swarm of microbes.

“Even at zero stress, it can spontaneously flow with a finite shear rate,” she says. “So it has exactly zero viscosity. It’s a superfluid!”

This is a very strange result. Superfluids – liquids that flow without friction – are rare, and have previously only been encountered at extremely low temperatures, close to absolute zero. If Fielding’s predictions are correct, this would be the first example of superfluidity at room temperature. Whereas the “traditional” superfluid, liquid helium, relies on the weird quantum physics of ultra-low temperatures to achieve perfect frictionlessness, Fielding’s active fluid simply relies on the hard work of billions of microbes swimming furiously.

So what’s it going to be used for? The applications of a room-temperature superfluid have yet to be invented, since no-one ever anticipated such a discovery, but they will surely be impressive. Ideas anyone?

Nonlinear dynamics and rheology of active fluids: simulations in two dimensions”, S. M. Fielding, D. Marenduzzo and M. E. Cates, Physical Review E 83 (2011) 041910