Thoughts from an active pensioner who is now somewhat past his Biblical "Use-by date"

"Why just be difficult, when with a little more effort you can be bloody impossible?"

Tuesday, 20 September 2011

Falling Satellite

According to the Telegraph, a NASA satellite is due to fall to earth sometime within the next few days and up to 26 fragments of various sizes are likely to hit the earth. They quote NASA as stating that the odds of someone being hit by a fragment as one in 3,200!
This is a total ludicrous figure! If it were true it would be totally unacceptable.

If we look at the maths, the total surface are of the earth is about 198 million square miles and thus the chance of a piece falling in any particular square mile is 198,000,000 to one, or allowing for 26 pieces, about 7.6 million to one. But a square mile is still quite a big space and you'd have to be pretty unlucky to be hit by a bit even if you were in that particular square mile.

Looking at it another way, the earth's population is stated to be approximately 7 billion, and if 26 fragments all hit someone, the chances of being hit are around 270 million to one. But of course, as only 30% of the earth is land, the probability is that roughly 2 out of three of the falling bits will end up in the world's oceans, so only nine bits are likely to land on solid ground.
I wonder who put the decimal point in  the wrong place when quoting 3200 to one?

1 comment:

  1. My first thought was that there are 7 billion people, so if one in 3,200 of them gets hit then that is a lot more than 26 fragments!

    Then I realised, I think they mean the chances of someone, somewhere, getting hit is 1 in 3,200 - i.e. the chance of any of those 7 billion getting hit.

    On that basis, your personal chance is one in 7 billion of 1 in 3,200. Or 1 in 22,400,000,000,000.