So what do we need to know?
Firstly, the Vatican is about 0.48km2.
Secondly, lets take a look at the frequency of lightning strikes in Rome. The best data I could find (whilst eating my lunch) came from this image.
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| http://geology.com/articles/lightning-map.shtml |
And if you zoom in on Italy is looks, to me, like that's about 5 flashes per year per km2. So that works out at about 2.4 flashes per year above the Vatican. But not all of those flashes are going to result in stikes. According Wikipedia only 25% of flashes result in a strike. So 0.60 times a year lightning stikes the Vatican.
Which means that there is 0.60/365 X 100 = 0.164% chance that lightning will strike the Vatican on the same day that a Pope resigns.
OK, so that's not exactly likely, but its hardly a rare occurrence (the lightning strike, that is). Its certainly a good coincidence but I'd hardly say it was a sign from God.
OK, so that's not exactly likely, but its hardly a rare occurrence (the lightning strike, that is). Its certainly a good coincidence but I'd hardly say it was a sign from God.
EDIT: A decimal point when missing in an early version of this post which resulted in a massive error in the area of the Vatican. Sorry, fixed now.
you cannot make sensible probability calculations about an event that already happened. (You can only calculate likelihood of a possible future event). Imagine saying "Yesterday I crashed into a green minivan that had a licence plate ABH6484. Of all possible licence plates, it is utterly unlikely that I would dent a mininivan that has just this exact licence plate, and on top of that, that I would crash into it just yesterday afternoon after writing a rude blogpost about the pontiff. So the green minivan must have been a sign from above"
ReplyDeleteMilkshaken, I must disagree. While it is true that probability calculations for events that have already occurred hold no predictive quality, they are interesting in that they give a measure of the severity of a coincidence. The example provided here is relevant because lightning is relatively uncommon as well as spectacular. Moreover, it has been-and is still by many people-perceived as and act of God. Your counterexample is not comparable since, while it may be uncommon, there is presumably nothing spectacular about the license plat ABH6484. But what if your name were Abraham Benjamin Harris and you lived at 6484 Walnut St. Wouldn't it have been quite a coincidence that you crashed into a car with your initials and address on the licence plate? It would be, wouldn't it? You can't deny that that would have been a pretty impressive coincidence! No, you can't! How impressive a coincidence? Well to answer that question, you'd have to calculate the probability of that happening even though it has already happened.
ReplyDeletewhat is one impressive coincidence (and what is not) is a quite arbitrary selection - it is only matter of your personal preference. You can "calculate the odds" by selecting how many independent variables must have conspired to get the one conspicuous event (and you can get differing numbers, according how many variables you take into account). My point is that such post-diction probability calculation is meaningless, it does not carry any predictive power and so on. Superstitions and fallacies about probability and statistics are pretty widespread - it keeps the gambling industry in business.
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