Is the human body obsolete? What threats do artificial life pose to humans? What if we become emotionally attached to a robot? Few people can interrogate these questions like renowned Australian performance artist Stelarc. Constantly blurring biological lines with robotics and virtual worlds, he is known for allowing his body to be controlled remotely via the Internet and strapping himself to the centre of a huge, six-legged spider-like machine. On 7 July, the jet-setting artist will fly into Ca