Sky Ear, floating above Greenwich Park London in September 2004, was a floating glowing carbon fibre cloud, embedded with 1000 helium balloons and electromagnetic sensors, and dozens of mobile phones. When activated, the sensor circuits co-ordinated to cause ultra-bright coloured LEDs to illuminate throughout the structure.

As people using phones at ground-level call into the cloud (flying up to 100m above them) they 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 affect the glow patterns of that part of the balloon cloud. Feedback within the sensor network creates ripples of light which change as the cloud goes through a number of different modes.

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