Near earth objects make tomorrow a little less than certain

Photograph of earth from spaceA couple of weeks ago, I wrote about unattainable uncertainty [see ‘Uncertainty is unattainable and near-uncertainty unaffordable’ on May 12th, 2021] and you might have thought that some things are certain, such as that tomorrow will follow today.  However, even that’s not certain – it has been estimated that there is a 1 in 300,000 chance in the next one hundred years of an asteroid impact on earth resulting in more than one million fatalities.  It might seem like a very small probability that you will not be around tomorrow due to an asteroid impact; however, as Sir David Spiegelhalter has pointed out, if that probability of fatalities related to an industrial installation, then it would be considered an intolerable risk by UK Health and Safety Executive.  By the way, if you want a more accurate estimate of the probability that an asteroid impact will prevent you seeing tomorrow then NASA provides information about the next Near Earth Object (NEO) to pass within 10 lunar distances (the distance between the moon and the earth which is 384,000 km) at https://cneos.jpl.nasa.gov/.  121 NEOs came within one lunar distance during the last twelve months of which the largest had a diameter of between 88 m and 200m, which is about the size of an Olympic Stadium, and came within 310,000 km; while the closest came within 8000 km, less than a Earth’s diameter which is 12,742 km, and was between 4.8 m and 11 m in diameter or about the size of two double-decker buses.  Spiegelhalter reassures us by telling us that there is no record of anyone, except a cow, being killed by an asteroid whereas tragically the same cannot be said about double decker buses!

Sources:

Reinhardt JC, Chen X, Liu W, Manchev P, Pate-Cornell ME. Asteroid risk assessment: a probabilistic approach. Risk Anal. 36:244–61, 2016.

Spiegelhalter D. Risk and uncertainty communication. Annual Review of Statistics and Its Application. 4:31-60, 2017.

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