Okay, suppose I want to travel backwards in time from 2010 to 1920. I make sure my cellphone is charged, I get into my time machine and I press the "Reverse" button. The widgets and whirligigs bend space-time until my reference frame is right beside the reference frames of those people in Charlie Chaplin's film. Then I press "Stop".
Now, how do I transfer myself from my reference frame to theirs so I show up on their film?
"It appears that many of you turn to Hebrew to escape the English...." -- Joseppi