London, July 21 : The next time you go to watch a circus, don't be surprised if you find the acrobats literally walking in the air, if an idea for an invisible cable made of carbon nanotubes works out.
Being narrower than the wavelength of light, nanotubes are normally invisible - as long as they are separated by more than one wavelength.
Now, according to a report in New Scientist, Nicola Pugno of the Polytechnic of Turin in Italy has calculated how many nanotubes would be needed to support a person, taking into account small defects that develop in the tubes during manufacture.
When held 5 micrometres apart, to keep them invisible, they would form a cable only 1 centimetre in diameter weighing a mere 10 milligrams per kilometre.
A plate with more closely spaced holes could slide along the cable, bringing the nanotubes closer, and so into view.
Further development of the idea might completely change acrobatic acts performed in the circus, as well as special effects used in movies.