The answer is obvious. It would be the lead story in every news broadcast, and would appear above the fold on the front page of every newspaper in the world until either; a. it struck, or b. scientists figured out how to prevent it.
And in the second instance, what portion of our resources, human and otherwise, would we devote to implementing plans to avert such a catastrophe? Would anyone ask if it was worth the money?
Yet this is exactly analogous to the situation we currently face. The climate crisis is potentially no less dire than the effects of a civilization-disrupting asteroid impact. So where are the headlines? Why are we not more worried?
This week I had the opportunity to speak to a group of college students at the University of Hartford. Their visual communication class had just completed a project designed to encourage their peers to act more sustainably and I was invited to critique their work. There were posters and other materials advocating things like changing light-bulbs, driving less, conserving water, and several other worthy ideas. Some of the work was quite good, with catchy slogans and attractive graphics. But I couldn't bring myself to give them much of a pat on the back for their efforts.
Changing light bulbs is all well and good, but I wanted to change the subject. Why aren't you more angry, I asked them. You are about to inherit a very fucked-up planet and you should be really pissed off. You should be marching in the streets. You should be organizing protests, sit-ins, moratoriums. You should be taking over the administration building and demanding change. You should be furious.
I am a child of the 60's, I told them. When I was in college the Vietnam war was raging. It was all we could think about. Students everywhere were united in opposition to the war. We were consumed with rage. We were mad as hell and we weren't going to take it anymore.
A whole generation took to the streets, staged protests - some peaceful, some not - and demanded change. And it wasn't only students. Millions of people raised their voices in unison and were heard. Activism played a major role in ending American involvement in that war. Nixon and Kissinger would have continued to prosecute the war but it became clear that the country would no longer support it. When people make enough noise, (enough being the operative word) government has no choice but to respond.
So why are we so passive about global warming? If left unchecked, the cost in human suffering will be no less than from any war. It will be greater. Where is the anger? Where are the protests? Are we sheep?
Personally, I blame the media. During the Vietnam era disturbing images of war appeared in every newspaper every day. Every night on TV we saw flag-draped coffins bearing the remains of young Americans being disgorged from airplanes. Back then the media did its job - we were not allowed to forget for a single day the cost of war.
There was something else, too. It felt personal. Very personal. I and millions of young men of my generation were subject to the draft. Like everyone else, I knew there was a very real possibility I might suddenly find myself on a battlefield in southeast Asia. Once there it was not at all unlikely that I might be killed, or worse, have to kill others. I was lucky, though.
Students today have nothing so tangible to concentrate the mind. But the threat to their future is, if anything, greater. Had I been sent to Vietnam there was a better than even chance that I could have returned home to resume a normal life. But none of us will be able to escape the consequences of a warming planet.
When are we going to do something about it?