theprof00 on 24 October 2013
Simple. We haven't seen time travellers because we haven't invented it yet.
In order to travel back in time, you need to have a receiver...after all, you cannot create something from nothing. No time travelers can travel to a period before the receiver is invented.
It makes no difference though. Soon we will all live in a digital world, where time travel is easily performed. Time travelers will be the hackers of the future.
