Let us pause to consider the Pentagon’s effort to shoot down USA-193, an intelligence-gathering satellite the size of a bus that went out of commission shortly after its launch in 2006 and then began hurtling toward Earth. A window of opportunity opened Wednesday night and soon the world will know whether it has been saved from peril.

This was a plan that I was originally behind 1,000 percent. Who among us wants to be hit by a falling bus? And the shooting-it-before-it-impacts strategy has worked well many times before, usually in movies starring Bruce Willis.

However, as details emerged, the plan began to seem somewhat less attractive. We’ve been sending stuff into orbit for half a century. An estimated 17,000 items, weighing up to 100 tons, have already fallen back into the atmosphere. The odds against one of them hitting a human being  I am thinking in particular of me  are, at worst, several million to one.

The critical thing about USA-193, according to the Pentagon, is that it was carrying an unusual amount of fuel, which could release toxic fumes on impact. According to Gen. James Cartwright of the Marines, vice chairman of the Joint Chiefs of Staff, it was the deadly gas threat that made President Bush decide to go for satellite assassination.