Suppose that astronomers around the world alerted us that a large asteroid is headed in our direction, and might collide with the earth in the year 2012.  The astronomers cannot give us a precise probability of collision because of many imponderables.  The laws of physics are, of course, uncontroversial, but there is some disagreement about the precision of the instruments used to measure the location of small objects at great distances.  It is also, of course, possible that the asteroid could be deflected by another object before it reaches the earth.  And astronomers concede that they do not know everything there is to know about outer space.  When pressed, the astronomers will say only that the scientific consensus is that a collision is “very likely,” and that, if it occurs, the consequences will be catastrophic.  To build a defense system—say, rockets that would intercept the asteroid and knock it off course—would cost hundreds of billions of dollars.

As is always the case, there are a few dissenters.  A highly regarded astronomer at MIT points out that astronomers have made incorrect predictions in the past and argues that a collision is possible but not likely.  A few physicists who do not specialize in astronomy argue that scientific instruments are not as precise as some people think, and the astronomers’ risk estimate should therefore be distrusted.  A scandal erupts when emails at the West Anglia Space Research Unit are released, and shows that some scientists tried to arrange a boycott of a journal that published a few articles of the skeptics.  At the same time, thousands of astronomers not connected with the West Anglia Unit continue to insist that the risk of a collision is very high.

A few questions.  In this scenario, would there emerge an industry of non-credentialed “astronomy skeptics” in the press and public comparable to the current batch of “climate skeptics”?  My instinct is that the world would quickly get to work building the rocket system, and disregard the views of the skeptics.  Is this right or wrong?  If it is right, is there some reason to think that climate science and astronomy are different, justifying the skepticism about climate science that does not (yet) exist about astronomy?

[I fear that some will snipe that responsible astronomers would not make such a prediction because of the difficulty of making long-term forecasts given current technological limitations.  If so, let’s just move the hypothetical into a future period when the technology is good enough to produce a “scientific consensus” but not complete agreement about all particulars among all people.]

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