[meteorite-list] Statistics for falls

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Sat Jun 19 01:12:12 2004
Message-ID: <40D3CB52.F398A555_at_bhil.com>

Hi, Mark,

    The method was simply this. First, imagine that we could find and count
every meteorite that falls on the entire planet. We just wait a year and then
count them BUT, we really can't do that, so... We scrape off a square mile and
cover it with white paper and wait 10,000 years, then count the meteorites,
divide by 10,000 and multiply by the number of square miles on the planet,
and...
    Hmmm, I can't wait 10,000 years (I'm really busy). We need a bigger target
so we don't have to wait so long. Wait a minute. The target doesn't have to be
all in one piece. If we had 1,000 patches placed at random all over the planet,
each being one square mile, we'd only have to wait 10 years to have good
results!
    In fact, the results would be better than one big patch, because all local
variations would be canceled out by putting many target patches all over the
place. So, how about 50,000,000 or so target patches, each about 10 square
meters, scattered all over the Unites States, and to make it more truly random,
we'd move the target patches around all the time, every day, putting them in one
spot for a few hours, then repositioning them someplace miles away for a few
hours, then moving them back again...
    You guessed it, the target patches are OUR CARS (and trucks). They total up
to a target patch of about... (scribble,scribble) 500 square miles or so. BIG
target. And the best thing is: we really pay attention to our cars. We love'em.
If a big honkin' rock breaks a window, dents the trunk, or punctures the roof,
WE NOTICE.
    The lady in New Zealand said about their house crashing meteorite: "If it
had fallen in the garden it would probably have been added to the pile of rocks
I am taking to the dump. Nobody would have known about it." Ruining the family
SUV is even more noticeable than hitting the house. What if it had just bounced
off the roof into the garden?
    I think using cars as the target does more to solve the "reporting" problem
than any other method. (However, I sometimes wonder how often a meteorite bonks
a car, the owner comes out in the morning, finds the big dent, sees the rock
lying in the gutter, and mutters, "Damn kids!")
    Anyway, you can find out how many cars are registered in the US in each
year, multiply by the average cross section of a car, get the total target size,
count the number of meteorite hits on cars per year for the last 70 years or so,
and calculate back to approximate a fall rate for the whole planet.
    Statistically, it is a sensitive enough method that the drop in the number
of US cars in the 1940's (World War II and gas rationing) shows up as a low in
meteorite car hits.
    Personally, I welcome any meteorites that have their eye on my 1996 Ford
station wagon. They're welcome to it. Lunaites, especially...


Sterling
--------------------------------------------------------------------------------------------------

minador wrote:

> Sterling Wrote:
>
> > where I outlined a different method of
> > estimating the fall rate and came up with a figure of 50,000 to 80,000 per
> year,
> > based on how many meteorites hit cars. The method is the same as is used
> in
> > nuclear physics to calculate "collisional cross sections."
>
> Wow, that's great to hear. Have there been any papers written on this
> subject?
>
> What is the convention wisdom regarding meteorite supply? Are they being
> "hunted out", or are hunter's just beginning to scratch the surface (of the
> earth)?
>
> Private replies are always welcome. As I said before, I don't want to take
> away from Tracy's post...
>
> Over & out,
>
> Mark B.
> Vail, AZ
Received on Sat 19 Jun 2004 01:12:51 AM PDT