When they began doing experiements in making the
atomic bomb, there was some speculation that they might set off a
universe-destroying chain reaction. However, I believe those worries were unfounded, because if it were easy, one of the
Billions of alien races out there would have done it already.
So all this business about the danger that
nukes or
weird physics experiments will set off some
Universe-Destroying Chain Reaction is bunk. This applies for the faster than
light speed chain reactions. I believe it's still possible that some race has started a slow wave of destruction that's racing here now.
It's the negative counterpart to the anthropic principle.