[meteorite-list] 1 in 3200 odds of human impact (help)
From: MexicoDoug <mexicodoug_at_meteoritecentral.com>
Date: Sun, 25 Sep 2011 00:31:12 -0400 (EDT) Message-ID: <8CE495316E9A1F3-221C-90358_at_webmail-m001.sysops.aol.com> Hi listers I'm very suspicious of this widely quoted 1 in 3200 that is being passed off as a scientific number by NASA. Not 1:3000, nor between 1:1000 to 1:10,000: but 1:3200. This foolishly precise assertation, which if you've read "The Little Prince" you immediately suspect it is overstated due to the author's calculations 70 years ago there...where a similar calculation is actually done ... Average cross sectional area of a person? (Depends if it is in the morning when everyone is praying, I guess, or in the afternoon when everyone is running out of work)...let's say: Cross section per person:18 inches by 18 inches (1.5 x 1.5 sq. feet) World population: 6.964 X 10^9 living souls World Area: 196,939,900 sq miles Calculations: * Cross section per person = 2.5 sq. feet * current world population occupies 624.3 square miles (a wee bit bigger than Guam, and smaller than Singapore) * people that could fit on Earth's surface: 2,196,000,000,000,000 (2.2 million X 10^9) * Fraction of Earth's surface that's "people" = 6.96 / (2,196,000) = 0.00000317 = People occupy *ONLY* 3.2 parts per million (3.2 ppm) of the earth's surface So, saving rounding till the end, each piece of UARS actually has a 1/315,457 chance of falling on people (1/0.00000317). In rounded numbers, that's about 1:320,000 per fragment ==> 26 fragments approximately 1:12,000 chance. I guess if you are American you need more space than if you are Indonesian, and changing it to a 18 inches X 17 inches would change the result by 6% ie, if 3200 were right for 18X18 it would now be about 1:3000, and that is one of so many assumptions making the 3200 number a total joke of fake scientific confidence. If you gave everyone a square yard ((91.4 cm)^2) instead, it would be in the 3000 range. But here are the defficiencies I think of looking at it this way: * this looks at the whole world vs. the limited satellite trace. A true measurement would do a little calculus along the path considering the population density and the probability of earlier or later entry which could change probabilities by an order of magnitude easily. * I think what I did would work for 26 darts, but not hunks of significant size compared to a person's area unit. * Finally there is the Sylacauga effect for bouncing material that will affect things another factor of 2, 3, 4 who knows... There must be a half dozen other complicating factors to do this right. Does anyone know what has been considered to arrive at the bogusly precise 3200-1 odds being fed to us? Love to hear any improvements on the above model (if you can call it a model) which I got the 1:12,000 as a streaming (unverified) starting point ... Kindest wishes Doug Received on Sun 25 Sep 2011 12:31:12 AM PDT |
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