[meteorite-list] 1 in 3200 odds of human impact (help)

Sun Sep 25 02:53:41 EDT 2011

...and of course, my calculation only applies to the
one-in-three falls over land, not the two-in-three
over water. Dilute one part of the calculation with
two parts of water...

What you're talking about --- that specious popular
precision --- is the result of achieving high precision
and low accuracy at the same time. This is what most
newspaper and press releases statistics achieve.
http://en.wikipedia.org/wiki/Accuracy_and_precision

Sterling K. Webb
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----- Original Message ----- 
From: "MexicoDoug" <mexicodoug at aim.com>
To: <bandk at chorus.net>; <Meteorite-list at meteoritecentral.com>
Sent: Sunday, September 25, 2011 1:27 AM
Subject: Re: [meteorite-list] 1 in 3200 odds of human impact (help)

> Thanks Kirk.
>
> I was more complaining about the ridiculous precision of the odds they 
> give and not meaning to suggest mine was a better order of magnitude, 
> but only that people read this sort of precision and naturally assume 
> there is some supercomputer and infallible black box behind it if they 
> start quoting things like 1:3200, when the reality of the situation is 
> that someone else could defend their same calculation and have it ten 
> or even a hundred times less in this example.  Also those such 
> probabilities are calculated on limited information.  Just look what 
> happened:  NASA: 1:3200 and coming down Friday evening.  Oops! Changed 
> orientation, our probability is bullhonkey (yet the media continues to 
> quote it), every assumption is changed.  The probability is now 
> 1:1,235.141592
>
> It's not an academic exercise; on the met-list it's of general 
> interest for those interested in meteorites striking people, houses 
> and even the occasional loveable crater-headed dog.
>
> But very seriously a risk assessment needs to be done when making such 
> decisions as converting used satellites into projectiles although no 
> one will agree on a universal level of risk that is "OK", the first 
> step is to estimate the probability.
>
> In the future it will be inevitable that this haphazard, seat of the 
> pants crashing, doesn't continue as earth adds hundreds of satellites 
> each year and we already have 5000 - 6000 up there plus about triple 
> that amount of debris, if I haven't guessed right.  Satellites will 
> need not only to make it up, but to have a safe plan to decommission 
> them, like the evolution of safety controls in the auto industry.  It 
> has to happen, though it's going to be a huge mess to sort out 
> agreements and give credits to poorer nations that haven't created the 
> current mess and are cash-strapped and then develop their satellite 
> networks.
>
> The risk assessment of a 1:10,000 of a minor asteroid hitting earth 
> causes all this commotion... imagine the zoo all this satellite mess 
> is headed to turn into.
>
> Hopefully we can figure out how to economically remove satellites 
> safely, or better yet create a cottage industry of salvage 
> entrepreneurs that can make a go at it and can be paid to remove scrap 
> as well by the offending parties...
>
> So, when NASA says 1:3200 - it just looks darn foolish and a bit 
> arrogant, too if not given with further explanation.  It's not like 
> this is a minor detail for scientists.  It is everyone's right to know 
> and no government's right to put innocents at higher risk, although 
> they do it all the time...
>
> Kindest wishes
> Doug
>
>
>
>
>
>
> -----Original Message-----
> From: Becky and Kirk <bandk at chorus.net>
> To: Meteorite-list <Meteorite-list at meteoritecentral.com>; MexicoDoug 
> <mexicodoug at aim.com>
> Sent: Sun, Sep 25, 2011 12:47 am
> Subject: Re: [meteorite-list] 1 in 3200 odds of human impact (help)
>
>
> WOW---some pretty good calculations and science there Doug----BRAVO!!
> NASA screws up yet again!!
>
> Kirk.....:-)
>
> ----- Original Message -----
> From: "MexicoDoug" <mexicodoug at aim.com>
> To: <Meteorite-list at meteoritecentral.com>
> Sent: Saturday, September 24, 2011 11:31 PM
> Subject: [meteorite-list] 1 in 3200 odds of human impact (help)
>
>
>> 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
>>
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