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Your secret superpower

By Matin Durrani

The March 2015 issue of Physics World magazine, a special issue about light in our lives that is now out in print, online and via our apps, contains a fascinating feature about an astonishing – and largely unknown – superpower that you perhaps don’t realize you have. It might sound bizarre, but using your naked eyes – and with no additional gadgets whatsoever – you can detect whether or not light is “polarized”. And in the video above, Louise Mayor, features editor of Physics World, tells you how.

Obviously you need some polarized light to look at – and one option is to look at ordinary, unpolarized light while wearing, say, a pair of polarizing sunglasses. Another option is to use a liquid-crystal display (LCD) computer screen. As Louise explains above, your best bet is to set the screen to plain white or blue – in fact, in the video we’ve included a few seconds of plain white screen. So if you click on “full screen” and pause the video at that point, you’ll have an instant source of monochrome, polarized light.

All you then need to do is to stare at the polarized light. It might take a bit of practice, but you should eventually become aware of an image at the very centre of your vision. It’ll look a bit like a small yellow bow tie crossed with a blue bow tie and is known as “Haidinger’s brush”, after the Austrian scientist Wilhelm Haidinger who first reported it in 1844. The blue bow tie is aligned with the electric field of the light you are observing, and so you can use this to work out which axis the light is polarized along.

Seeing Haidinger’s brush takes a bit of practice – if you’re looking at an LCD display, you can check if you’re doing things properly by tilting your head slowly from side to side and the brush shouldn’t change orientation. You can find out more about this weird effect in the feature article, which is written by David Shane from Lansing Community College in Michigan.  It’s worth persevering, Shane says, because if you can see the brush, then you can look for polarized light anywhere. “Don’t give up if you can’t see it at first!” he insists.

Note that Haidinger’s brush is an “entoptic” phenomenon, which means that the image is created in the eyeball itself, so you’ll never see a photograph of it. As for what causes Haidinger’s brush…well that’s still a mystery.

Physics WorldIf you’re a member of the Institute of Physics (IOP), you can now enjoy immediate access to the new special issue about light in our lives with the digital edition of the magazine on your desktop via or on any iOS or Android smartphone or tablet via the Physics World app, available from the App Store and Google Play. If you’re not yet in the IOP, you can join as an IOPimember for just £15, €20 or $25 a year to get full digital access to Physics World.

For the record, here’s a rundown of what else is in the issue, which is a celebration of light in this, the International Year of Light.

• BICEP2 withdraws cosmic claims – Scientists working on the BICEP2 telescope have backtracked on claims that they had discovered the first evidence for cosmic inflation, as Tushna Commissariat reports

• The mystery of the disappearing physicist – Did the physicist Ettore Majorana not commit suicide, as is widely believed, but go on to live a secret life in South America? Edwin Cartlidge weighs up new evidence

• Leading light – UN secretary-general Ban Ki-moon outlines the importance of the International Year of Light, while physicists reveal what the year means to them

• Meet the kaleidoholics – Two centuries after the kaleidoscope was invented, Robert P Crease stumbles into an incredible world as he visits a physicist who collects these and other “philosophical toys”

• Lighting up the world – More than a billion people across the globe still do not have access to electric lighting. Jon Cartwright talks to those who are turning to light-emitting diodes to supply this most basic feature of modern life

• Night skies get the blues – Light-emitting diodes generate light both cheaply and efficiently, yet by giving off lots of blue light they could worsen light pollution and hamper the quest for dark skies. Gabriel Popkin reports

• The laws of light – Martin Hendry looks at the significance of Maxwell’s equations to our understanding of light

• Unveiling your secret superpower – If you thought weird visual abilities belonged to the realm of the few, think again. David Shane describes a bizarre talent that most sighted human beings have but probably don’t know about

• Rooms with a view – Sidney Perkowitz explains how the camera obscura (“dark room”) and camera lucida (“luminous room”) are still relevant today in science and art, despite the availability of much more modern cameras

• More than meets the eye – New camera technologies are pushing the boundaries of imaging far beyond what the eye can perceive. Matthew Edgar, Miles Padgett, Daniele Faccio and Jonathan Leach explain how three of these novel cameras work and outline some future applications

• A man, a plan, a bomb – Margaret Harris reviews the play Oppenheimer at the Royal Shakespeare Company’s Swan Theatre in Stratford-upon-Avon

• A multiverse play divides opinion – Robert P Crease reviews the play Constellations at the Samuel J Friedman Theatre in New York

• Your career questions answered – Not sure what to do after you graduate? Join the club. Margaret Harris explores the findings of a recent survey that asked physics students to share their career concerns and aspirations

• Acronyms Anonymous – Rick Trebino looks at some amusing acronyms from his physics career

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  1. John Duffield

    Interesting. I saw something, smaller than I expected. It seemed to be accentuated when I looked at the white screen with one eye only and then swapped eyes.

  2. M. Asghar

    The Haidinger’s brush is known to be much stronger for many species in th matrix of life than for the human beings. This difference is likly to be due to the difference in the evolution of the “optical systems” for the different species and, here, the man’s rather sharp environment-deciphering intelligence and his being acive mostly only during the daylight, may have been his undoing in this optical domain.

  3. Hi John, I’m pleased to hear you saw something. What I find strange is that when I tilt my head while looking at a white part of my monitor, the yellow bow tie (which I find most apparent) flips from one orientation to another (from being aligned top-left to bottom-right, to bottom-left to top-right). I am trying to get hold of a linear polariser so I can check if for some reason my screen puts out polarised light with two axes of orientation.

    M. Asghar, did you see Haidinger’s brush?

  4. Pete Wagner

    I have two large monitors on my desk, a 30″ Dell 2560×1600 and a 32″ Acer 3840×2160. I can see the effect on both monitors but only when I tilt my head to one side to initiate it. Having done this I can then tilt my head upright again and continue to see it but the effect then subsides. Keeping my head tilting from side to side keeps the effect visible but the “image” tends to change angle slightly with respect to the monitor. On the Dell the blue is vertical and the yellow horizontal. It is the other way round on the Acer. If I view through circularly polarised glasses, the passive type you get at some 3D cinemas, the entire Dell screen appears the same shade of blue as in the “brush”. If I rotate the glasses through 90 degrees, the entire screen then becomes the same shade of yellow as in the “brush”. The effect is reversed on the Acer. I hope this is helpful.


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