Off topic: the odds of being hit by space debris

Artistic rendering of Tiangong 1, source BBC

ESA says [1] it’s 106 times more likely to be hit by a lightning twice in the same year that to be hit by Tiangong 1’s debris. There are 2 recorded incidents [2] of space debris that caused harm to people, the earliest recorded in 1979. According to [3], chances of being struck by lighting in a given year are 10-6. I guess being hit twice is something around 10-12 which puts the ESA-computed odds at 10-18.

According to [4] there are currently ~4500 satellites orbiting earth. I assume that that’s half the number of satellites there were ever in orbit, so 9000 in total, ever. Add to that the 9000 rocket launches necessary to get the satellites into orbit, that makes 18000 possible causes of space accidents. Of those 18000 possible causes there were 2 recorded incidents since 1979 (see intro) which computes the odds at about 10-4 or 1:10000. Happy Easter everyone 🙂


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