From Alan Robinson
The paradoxes referred to when time travel is discussed always seem to involve sentient beings (20 September, p 28). Someone goes back in time and alters the time line or carries information back with them.
Is it possible to specify a significant paradox involving only non-sentient objects – say a rock, or an electron? Come to that, since all electrons are identical, would it mean anything to say that a particular electron had been sent back in time?
Griffydam, Leicestershire, UK
