View all newsletters
Sign up to our newsletters

Support 110 years of independent journalism.

  1. Science & Tech
25 April 2012

Hiding in plain sight

By Michael Brooks

The Easter holiday rush is receding into distant memory. The only thing airport security personnel have to worry about is what happens when everyone starts arriving for the Olympics. That, and the helpful physicists who have worked out how to smuggle a gun through a metal detector.

It all started as a bit of harmless blue-sky thinking. In the late 1960s, a Russian physicist pointed out the fun you could have if you invented a material that bends light in the opposite direction to normal. You could use it as an invisibility cloak, he said: just as water diverts round a rock in a stream by going first to one side, then back to the other, light bent in two different directions as it passed an object would give a viewer the impression that the light had travelled in a straight line and that the object simply wasn’t there.

Oh, how everybody laughed. Then, in 2000, someone turned this ridiculous fantasy into reality. John Pendry of Imperial College London showed how to create “left-handed materials” that would bend microwave radiation the wrong way. The practicalities were a little cumbersome and it didn’t work with visible light. But still, it was surprising, impressive and fun, in a nerdy kind of way.

Over the past decade, the technology has matured. At first, left-handed materials were constructed from intricate arrays of copper rings and could only hide tiny objects from a microwave detector. Now, we have invisibility “carpets” made from cheap and widely available crystals of the mineral calcite. They are able to hide objects the size of your thumb – and they work in visible light.

That technology is not yet going to smuggle a gun through airport security, though. Even if the X-ray machine doesn’t make the outline obvious, the magnetic field from the steel triggers an alarm. But a paper recently published in the journal Science can get you round that obstacle.

As it turns out, you can cloak a metal’s magnetic field for less than £1,000. First, wrap your gun in a layer of superconducting tape. Magnetic fields cannot pass through a layer of superconductor, so the scanner wouldn’t see the gun’s field. The scanner would see the superconductor’s field, though. However, this can be countered by adding a layer of flexible magnetic strip, rather like that found on the back of a fridge magnet. The researchers showed that this combination of readily available materials does a reasonable job of cloaking a magnetic field.

Touching the void

OK, it’s still not quite a credible threat. The superconductor has to be kept at liquid-nitrogen temperatures and a cloud of nitrogen vapour coming out of your hand luggage might raise a few eyebrows. A simple thermal detector would certainly put paid to any gun-smuggling plans.

But the physicists aren’t beaten yet. While some have been content to bend light as it travels through space, Martin McCall of Imperial College London has played around with bending light as it travels though time.

The technique involves slowing down and speeding up light inside an optical fibre – something that physicists have learned to do with astonishing skill in the past few years. McCall now has a blueprint for a device that doesn’t just make things invisible; it makes it look like they never even happened. It only works on technologies with an optical fibre feed, such as a CCTV camera. Nevertheless, in principle, we now know how to create the illusion of a void in both space and time – a void that could plausibly be exploited to evade surveillance technologies. Of course, it’s ridiculous. But where these troublesome physicists are involved, nothing remains ridiculous for long.

Michael Brooks’s “Free Radicals: the Secret Anarchy of Science” is published by Profile Books (£12.99)

Content from our partners
The promise of prevention
How Labour hopes to make the UK a leader in green energy
Is now the time to rethink health and care for older people? With Age UK

Select and enter your email address Your weekly guide to the best writing on ideas, politics, books and culture every Saturday. The best way to sign up for The Saturday Read is via saturdayread.substack.com The New Statesman's quick and essential guide to the news and politics of the day. The best way to sign up for Morning Call is via morningcall.substack.com Our Thursday ideas newsletter, delving into philosophy, criticism, and intellectual history. The best way to sign up for The Salvo is via thesalvo.substack.com Stay up to date with NS events, subscription offers & updates. Weekly analysis of the shift to a new economy from the New Statesman's Spotlight on Policy team. The best way to sign up for The Green Transition is via spotlightonpolicy.substack.com
  • Administration / Office
  • Arts and Culture
  • Board Member
  • Business / Corporate Services
  • Client / Customer Services
  • Communications
  • Construction, Works, Engineering
  • Education, Curriculum and Teaching
  • Environment, Conservation and NRM
  • Facility / Grounds Management and Maintenance
  • Finance Management
  • Health - Medical and Nursing Management
  • HR, Training and Organisational Development
  • Information and Communications Technology
  • Information Services, Statistics, Records, Archives
  • Infrastructure Management - Transport, Utilities
  • Legal Officers and Practitioners
  • Librarians and Library Management
  • Management
  • Marketing
  • OH&S, Risk Management
  • Operations Management
  • Planning, Policy, Strategy
  • Printing, Design, Publishing, Web
  • Projects, Programs and Advisors
  • Property, Assets and Fleet Management
  • Public Relations and Media
  • Purchasing and Procurement
  • Quality Management
  • Science and Technical Research and Development
  • Security and Law Enforcement
  • Service Delivery
  • Sport and Recreation
  • Travel, Accommodation, Tourism
  • Wellbeing, Community / Social Services
Visit our privacy Policy for more information about our services, how New Statesman Media Group may use, process and share your personal data, including information on your rights in respect of your personal data and how you can unsubscribe from future marketing communications.
THANK YOU