Asteroid Impacts - A Probability of One in 250 Thousand

We live in an era of unprecedented safety. The 20 r century is the first ever moment when we have known how to defend ourselves from such impacts, which occur once every 250 thousand years or so. We do not know the probability of a spontaneously occurring, incurable plague, but we may guess that it is unacceptably high. If our civilization moves out into space in order to hedge its bets, as reese and hawking both rightly advise, a gamora burst in our galactic vicinity would still wipe us all out. Such an event is thousands of times rarer than an asteroid collision. But when it does finally happen, we shall have no defence against it without a great deal more