
Why extremely rare events keep happening all the time - eplanit
http://www.chicagotribune.com/news/sns-wp-blm-rare-comment-4355e7ec-370a-11e6-af02-1df55f0c77ff-20160620-story.html
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shardinator
There's also another phenomenon at play. The probability that a particular
rare event occurs is very rare. But the probability that any one of many, many
possible rare events occurs is actually much higher.

More concretely: If you have a billion possible independent events with a one
in a billion probability of occurring on any given day. Then on average one of
those incredibly rare events will happen everyday.

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kqr
This is known as the Texas sharpshooter fallacy. We observe one out of a
billion unlikely events and – after the fact – draw our bullseye around that
observation and say "what are the odds the particular thing under our bullseye
happened?"

Of course, it's probabilistically invalid to decide on the target after you've
observed which event actually occurred. Feynman exemplified this as

> _You know, the most amazing thing happened to me tonight... I saw a car with
> the license plate ARW 357. Can you imagine? Of all the millions of license
> plates in the state, what was the chance that I would see that particular
> one tonight? Amazing!_

If Feynman had walked into the parking lot with no prior knowledge of it and
said "car number 5 on my right will have the license plate ARW 357" then this
truly would have been amazing. But given that he saw the license plate first,
it's not as amazing anymore.

The same principle applies whenever someone says "Of all the mates my
ancestors could have met, they met the specific configuration of mates which
produced _me_ as an offspring, several generations down the line. What are the
odds?" Well... that was kind of bound to happen. There were billions of
possible offspring that didn't happen! One of them had to happen for anyone to
be able to say that.

See also: weak anthropic principle.

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shardinator
Thanks! Hadn't heard of the Texas sharpshooter fallacy.

