時光機 2

It is possible to affect the past, but not to change it.

The Novikov Principle does not allow a time traveller to change the past in any way, but it does allow them to affect past events in a way that produces no inconsistencies — for example, a time traveller could rescue people from a disaster, and replace them with realistic corpses seconds before it occurs.

— Wikipedia on Novikov self-consistency principle

2010.04.25 Sunday (c) All rights reserved by ACHK