## Meteor or meteorology?

Cosmic Variance presents an estimate of the chance that Air France flight 447 from Brazil was hit by a meteor. The conclusion:

That’s a one-in-twenty chance of some plane going down for this reason in that 20 year period. Extrapolating to all flights ever would require a better estimate of total flight hours, but it’s not twenty times the number in the past 20 years, for sure – that is, it’s not yet close to one.

Obviously there are a lot of uncertainties in this estimate; perhaps a factor of two from the number of meteors of sufficient mass per day, the average flight duration and number of flights?

Anyway the meteor idea is not crazy, though not likely. The weather seems more likely to be at the root of the tragedy…but we may never know. One thing, though, is clear: if we keep flying big planes at high altitude, eventually one will get hit by a meteor.

The last sentence is true independent of any data!

A response to the computation by one of the readers of that blog is also worth quoting:

I am also an astronomer. On any given day, many tens of thousands of meteors enter our atmosphere. These were extensively studied using radio scatter off of meteor trains, and they have been used for meteor burst communications. Nearly all of these burn up in the atmosphere before hitting the earth. Common sense tells you that if thousands of these fell to earth each hour, then we’d all have holes in our roofs.

Finally, a more accurate computation (using the same assumptions) reported in the comments:

Using the numbers as stated: The number of events is 20 years times 125 events per hour. The probability of each intersecting the proportion of the globe not covered by plane: one minus 2 billionths. Raise that probability to the power of the number of events, and subtract from one.

The chance of every meteor missing would come to a shade under 0.96, I think. So the chance of at least one hit would be a shade over 4%. If the numbers were right.

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