sky ear

sky ear was last launched september 15, 2004, but i managed not to hear about it til now.

Sky Ear is a non-rigid carbon-fibre "cloud", embedded with one thousand glowing helium balloons and several dozen mobile phones. The balloons contain miniature sensor circuits that respond to electromagnetic fields, particularly those of mobile phones. When activated, the sensor circuits co-ordinate to cause ultra-bright coloured LEDs to illuminate. The 30m cloud glows and flickers brightly as it floats across the sky.

As people using phones at ground-level call into the cloud (flying up to 100m above them) they are able to listen to distant natural electromagnetic sounds of the sky (including whistlers and spherics). Their mobile phone calls change the local hertzian topography; these disturbances in the electromagnetic fields inside the cloud alter the glow patterns of that part of the balloon cloud. Feedback within the sensor network creates ripples of light reminiscent of rumbling thunder and flashes of lightning.