# Talk:Palermo Technical Impact Hazard Scale

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## Background hazard

What is the "background hazard" exactly? Jheijmans

Excuse my probable innumeracy, but how is a 1 in 63 event 950% more likely than a 1 in 16000 event? 100 * ((1/63)/(1/16000)) - 100 = 25296 -- ~ 25000%,more likely, no? 950% is about right for 1.02 -- 10^1.02 =~ 10.5. I suspect the background risk is actually higher than 1/16000. Mike Linksvayer 05:44, 26 Dec 2004 (UTC)

I think 16000 probably came from the energy of the 2004MN4. The annual background risk of a collision with that energy is 0.03 * 1600^-0.8 which would be 0.001%. This number is then multiplied by the number of years till possible impact, or ~25 in this case, so 0.025% background risk. 10 times that is only 0.25%, so I must be off by a factor of 10 somewhere, but I can't see it. In any case, I suspect the background risk for a similar event over the next ~25 years is around 1 in 500, not 1 in 16000. (the 1/63 risk for 2004MN4 seems to have been updated to 1/45). Mike Linksvayer 06:16, 26 Dec 2004 (UTC)

I do believe that the Palermo Scale has gone up to 1.10 for 2004 MN4 has it not?

Where does the kinetic yield slot in exactly? The formula I see has space for chance of hitting, chance of something hitting, and time. Nothing about yield in there. Supersheep 22:53, 24 July 2006 (UTC)

No, I don't see it either. They should be separate anyway, or at least a scale should be available that separates the two. If we are asking about a particular object, of known size and velocity ("yield") then you are only interested in its chance of hitting you, and the Palermo or whatever scale just serves to muddy the waters, so to speak. Kortoso (talk) 20:10, 1 October 2013 (UTC)