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

From: Stuart McDaniel <actionshooting_at_meteoritecentral.com>
Date: Sun, 25 Sep 2011 15:38:20 -0400
Message-ID: <44B5B898792346FC8BCC7A74398CF09A_at_StuartMcDaniel>

Maybe they were calculating odds in the US only at the 1:3200.



Stuart McDaniel
Lawndale, NC
Secr.,
Cleve. Co. Astronomical Society
IMCA #9052
Member - KCA, KBCA, CDUSA
-----Original Message-----
From: MexicoDoug
Sent: Sunday, September 25, 2011 12:31 AM
To: Meteorite-list at meteoritecentral.com
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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Received on Sun 25 Sep 2011 03:38:20 PM PDT