• Question: What are metamaterials exactly? Can a closed body (body should have separate inner and outer surface areas; imagine a hollow cube) be created such that it absorbs all radiations on its front surface and mimics those same radiation at the same time out from the opposite surface and VICE VERSA...? I think Black body radiation should not be violated as body is not absorbing energy...and if not energy from inside dissipates...then this body should be invisible!! I really want to know whether there is any way it can differentiate between the photons it is absorbing and emitting on the same side due to the VISE VERSA...

    Asked by sanban to Chris, Dave, David, Fiona, Jack on 21 Jun 2013.
    • Photo: Chris Mansell

      Chris Mansell answered on 21 Jun 2013:

      Metamaterials are materials that have been very carefully designed so that they affect the propagation of waves (e.g. light waves or sound waves) in interesting ways. They do this by have pattern features in their structure that are smaller than the wavelength of the waves with which they are designed to interact.

      I am not sure I have fully got to grips with the device you are envisioning. However, if you are interested in making things invisible, there has been quite a lot of work done in this area:


    • Photo: David Freeborn

      David Freeborn answered on 22 Jun 2013:

      Metamaterials are materials that are able to get completely new properties by combining other materials in a particular way.

      For example, by arranging gold and copper in certain shapes and patterns we can make a material that combines their properties in a particular way, and also has some entirely new properties. We can design metamaterials that can guide light rays in a particular way.

      Metamaterials might be able to make objects “invisible” by guiding the light rays around the object. If we can make it work, it will be far, far more effective than any of the currently “invisibility cloaking” devices, based on optical sensors and computers, like this:

      British scientists are putting research into making an invisible tank.

      We might also be able to make metamaterial “cloaking devices” for magnetic fields and for heat as well.

    • Photo: Dave Farmer

      Dave Farmer answered on 23 Jun 2013:

      Hi sanban,

      When an electromagnetic wave travels through a ‘normal’ material, it is the electric part of the wave that interacts strongly with the structure. In metamaterials, the structure is designed to interact with the magnetic part of the wave as well. This can give rise to exciting new properties such as materials with a negative refractive index! This allows structures to be made that can control the path of electromagnetic waves (such as light) in new ways.

      I’m not quite sure what it is you’re asking with the second part of your question. Metamaterials are able to bend electromagnetic waves around objects, making them invisible as you suggest. It would depend on how your cube was made, but if each face was the same then I don’t think it would appear any different from one way or the other.

      Hope that answers your question, if not, let me know and I’ll have another go!