Reality Check

Prof Terry Rudolph speaks to New Scientist

Reality, relativity, causality or free will Take quantum theory at face value and at least one of them is an illusion – but which, asks Michael Brooks. At first, it looks like an ordinary mirror. But it's not. It is 'half-silvered'. Half of the light that hits it is reflected. The other half passes straight through. This is not in itself extraordinary… It's what they do to the individual photons of light that's the strange thing. Peer too closely, and these looking glasses might destroy your very perception of reality. They could leave you unsure where or even who you are, and make you question whether you exist at all. They might even so skew your notions of cause and effect that they leave you wondering whether you, rather than the mirror, are to blame for all this. The question is whether science gets any more profound than what happens at a half-silvered mirror. 'I don't think it does, ' says Terry Rudolph [Physics], a physicist at Imperial College London