I have probably told this story somewhere before. If so, bear with me.
September 11, 2001, happened right at the beginning of my final year of law school. My school had, in addition to the fall and spring semesters, a winter semester where the 2Ls and 3Ls would take one course concentrated into the space of something like three weeks. In the wake of the terrorist attacks, Professor Philip Heymann, with a couple of others, offered a winter semester course called "Terrorism in America." I took the class.
One morning, I was sitting in the back of the room with my coffee, still waking up, and Heymann decided to cold-call me. "Can you think of a situation," he asked me, "Where the world would face a threat that would cause all countries to band together to oppose it?"
I'm paraphrasing, but that's in substance the question he asked. I assumed (and still assume) that he was fishing for some sort of terrorist threat as an answer, but even in my days at Harvard, I was not so naive as to think that any earthly threat could get all nations to band together. So I gave him the only answer I could think of:
"Well, maybe if a large asteroid or comet or something was headed toward the earth."
The class laughed at me. Heymann was not impressed, and said that he had been looking for a more realistic response.
He moved on, and I said nothing further, but in my mind, I was sort of incensed. A comet or asteroid threatening the earth was unlikely, was it? The way terrorists hijacking planes on U.S. soil and crashing them into major landmarks might also seem unlikely on September 10, 2001?
Anyway, fast forward to a few weeks ago, when The Atlantic Monthly ran a cover story on the threat of asteroids hitting the earth. To say nothing of the various news pieces that have run about the threat, both before and after 2001.
What I'm trying to say is that I was right, and Heymann was wrong, however however far-out the threat may appear. If you'll forgive my pessimism, I still think we're far more likely to get smacked with a huge asteroid than to bring all countries together to fight a terrorist threat, and now that I think of it, I don't even know that I believe the Asteroid Menace would bring world unity. And if we do get hit with an asteroid or a comet, it will suck, but at least chances are that those who laughed at me or dismissed my concerns will go down in the same extinction event that takes me out.
I would never wish asteroid-related harm on anyone, but if large numbers of mankind are wiped out, it would be infinitesimally preferable for it to happen in a way that proves me right about something.