Stephen Black writes on the upcoming space satellite spectacular:
>How great is the risk? NASA is quoted in a slightly garbled
>statement in _The Telegraph_ that there's a "1-in-3,200 chance
>a part a satellite part could hit someone".

>I've been pondering what meaning to attach to that statement…
>[…]
>Alternatively, perhaps they only mean that for satellites in a
>situation similar to that which NASA warns us about, in only 1
>out of 3,200 occasions of one falling down will it off even a single
>unfortunate individual out of the entire world's population…

>Unless I hear otherwise, that's the one I'm going with.

And you're right to do so! The report from an NPR Science Correspondent 
clarifies this point:

NASA has actually calculated the odds that someone might get hit by 
this satellite. Mark Matney, an orbital debris scientist at NASA's 
Johnson Space Center in Houston, says the risk is 1 in 3,200.

"That 1 in 3,200 is the probability that someone, somewhere on the 
Earth will be hit by a piece of debris of sufficient size to cause 
injury," says Matney.

But Matney says your own personal risk of being hit by a piece of this 
satellite is far lower: "It's something like one in trillions, for any 
one person."

http://www.msnbc.msn.com/id/44462231/ns/technology_and_science-space/t/falling-satellite-poses-little-risk-public-nasa-says/#.TnmlOzD_l4Y

Allen Esterson
Former lecturer, Science Department
Southwark College, London
[email protected]
http://www.esterson.org

--------------------------------------------------------------
From:   [email protected]
Subject:        Statistics question: Death from the skies?
Date:   Tue, 20 Sep 2011 10:21:05 -0400
Although this is not directly psychology-related, our investment in
statistical analysis in psychology makes it so. Besides, who else am
I gonna call?

NASA warns us of  lurking risk of death from above
(http://tinyurl.com/3jygt52 ), "within weeks".

How great is the risk? NASA is quoted in a slightly garbled statement
in _The Telegraph_ that there's a "1-in-3,200 chance a part a
satellite part could hit someone".

I've been pondering what meaning to attach to that statement.  When I
checked just now, the world population was 7,147,958,331 and
counting. Dividng this figure by the stated chance of death by
satellite gives a figure of over 2 million expected deaths. Now
either this is absurd, or we're loooking at a major looming tragedy.
The article, after all, does say that "senior space agency officials
admitted they were "concerned" about the risk to billions of people."

Perhaps they mean that the risk only applies to those under the
flight path of the satellite. But that's little comfort when we're
told that the satellite "travels over a large band of Earth, avoiding
only areas close to the poles".

Alternatively, perhaps they only mean that for satellites in a
situation similar to that which NASA warns us about, in only 1 out of
3,200 occasions of one falling down will it off even a single
unfortunate individual out of the entire world's population. This is
an almost unimaginably small risk for each of us.  If that's the
case, then all this NASA stuff is merely Chicken Little.

Unless I hear otherwise, that's the one I'm going with. I'm coming
out from under the bed now.

Stephen

--------------------------------------------
Stephen L. Black, Ph.D.
Professor of Psychology, Emeritus
Bishop's University
Sherbrooke, Quebec, Canada
e-mail:  sblack at ubishops.ca



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