Invisible Wi-Fi revealed through light graffiti

The ghost out of the machine? In a project he is calling "Digital Ethereal", artist and researcher Luis Hernan at the University of Newcastle in the UK has rendered the invisible visible -- revealing in red, yellow, green and blue the Wi-Fi signal strength in the world around him.

He has called his device the Kirlian Device -- named for Russian inventor Semyon Davidovich Kirlian, who discovered Kirlian photography, a technique for photographing electrical discharges, usually invisible to the naked eye. But his project has something of the spiritual about it.

"This project came about as a design discourse on digital technologies, and the invisible infrastructure underpinning it. I believe our interaction with this landscape of electromagnetic signals, described by Antony Dunne as Hertzian Space, can be characterised in the same terms as that with ghosts and spectra. They both are paradoxical entities, whose untypical substance allows them to be an invisible presence," Hernan wrote on his website.

"In the same way, they undergo a process of gradual substantiation to become temporarily available to perception. Finally, they both haunt us. Ghosts, as Derrida would have it, with the secrets of past generations. Hertzian space, with the frustration of interference and slowness."

Quite simply, the Kirlian Device measures the properties of Wi-Fi signals in its immediate vicinity, and shows a corresponding colour from red through to blue -- red for a strong signal, through to blue for a weak one. As Hernan moves around, he uses long exposure photography to reveal Wi-Fi "ghosts" -- what he dubs "wireless spectres".

"The device is moved through the space, which is then registered in a long-exposure photograph," Hernan told Discovery. "This process lasts for several minutes, and due to the brightness of the device, my figure is ghosted away in the process. In some pictures you can see my feet or even my blurred head underneath the light strikes."

For the purpose of his project, Hernan built his Kirlian Device out of an Arduino UNO board and Wi-Fi Shield, connected to a strip of LED lights -- but he's also released a free Android app so that users can try it for themselves, and invited potential collaborators to drop him a line via his website.