From John Davenport
Both Sepehr Ehsani’s letter (21 January, p 28) and the review of How to Build a Time Machine (10 December 2011, p 52) assume that travellers from the future will be visible to our senses or to our instruments. Is there any proof of this? Perhaps we are surrounded by trillions of gawpers. All the world’s a stage?
Kenley, Surrey, UK
