Saturday, November 28, 2015

What Are the Chances, Part 1

Did you ever hear that on the day the US tested the first atomic bomb (the fission bomb), known as the Trinity test, scientists warned that there was a slight chance it might start a chain reaction in the atmosphere that would destroy the world?

It some ways, it appears the story is true; in others, it appears a myth…or at least, an exaggeration.

First, you have to consider that scientists would never say there is zero probability of an event, especially one as poorly understood as the atomic bomb was at the time.  Their caution was evidently warranted in this case, as their prediction of yield (between 5 and 10 kilotons of TNT) turned out to be quite different from our modern day estimate (21 kilotons of TNT).

But even with that caveat, are we talking about a 1 in 1,000 chance?  1 in a million?  Even less?  This is where the story gets a bit more murky.

It was the analysis of Edward Teller, known as “the father of the H-bomb” (fusion bomb) that puts the probability of total annihilation due to the fission bomb high enough to create concern.  Teller was, as the name implies, and an advocate of the more powerful fusion bomb, even as the fission bomb was being developed and he was calculating his estimates of doom.  I am not saying he ‘cooked the books’ to support his preferred option, but for an individual generally thought to be one of the inspirations for the character Dr. Strangelove in the movie by the same name, maybe it’s possible.  All we know is that when Oppenheimer asked Hans Berthe to verify Teller’s conclusion, he could not.  He considered total destruction so implausible as to be impossible, which may be as close as a scientist ever gets to saying ‘the probability is zero’.  Oppenheimer agreed and the project went forward.

But good scares do not die easily.  Evidently, on the day of the Trinity test, Enrico Fermi started taking bets on whether the bomb would destroy the world, or only New Mexico.  Who knew scientists had a sense of humor.  He was joking, right?

Now, having drafted this post and in re-reading it, I have to ask:  did I really write that “scientists would never say there is a zero probability of an event”?  What I meant to say was, there is a probability approaching zero that scientists would say there is zero probability.  After all, I have to be true to the scientist in me...

Happy Writing,

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