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R: Lyrids and Meteorite Fall Statistics

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volpedo@tin.it

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> Da: Bernd Pauli 
> A: meteorite-list@meteoritecentral.com
> Oggetto: Lyrids and Meteorite Fall Statistics
> Data: sabato 18 aprile 1998 23.54
> 
> Hi All,
> 
> Al wrote:
> 
> The statistics are interesting ones but I would like to point out a
> possible important factor. People tend to be outside more in the months
> mentioned there for they are out to witness the falls more during those
> times than in the winter months. Therefore the statistics could be
> misleading.
> 
> 
> My main concern was to point out that usually meteors and meteorites are
> different phenomena and that George’s remarks ‘the encounter is best to
> occur in the late afternoon or early evenings’ refer to meteorites and
> not to meteors.
> I am well aware that statistics are never quite unbiassed unless you
> really have 100% the total amount, quantity, number of whatsoever.
> Meanwhile a lot more people are outside any time of the year in both
> hemispheres, so I think the bias is increasingly decreasing. But
> statistics are helpful in showing trends and tendencies.
> 
> I’d like to add that I started evaluating statistical surveys on
> meteorites in the mid-80s when I started typing the ‘Big Blue Book’ into
> my Commodore 64 (!!!) page after page and made repeated acqaintance with
> ‘Out of memory’ messages. This interest in statistics was aroused by
> Heide’s booklet ‘Kleine Meteoritenkunde’ (2nd ed., 1957/ 3rd ed. 1988 -
> revised and updated by F. Wlotzka from the MPI, Mainz) and, of course,
> by Brian Mason’s Meteorites (1962). I wanted to find out if anything had
> considerably changed over the years but that was not the case. Results
> would change drastically if there were such a bonanza of falls
> comparable to all those Antarctic and Hot and Cold Desert finds.
> 
> 1) Let’s now make a difference between the Northern and the Southern
> Hemispheres and look at the statistical data again (as culled from my
> database):
> 
> (a) There are 97 documented falls for latitudes North and 12 for
> latitudes South in June.
> (b) There are 56 documented falls for latitudes North and 11 for
> latitudes South in December.
> 
> 2a) Now, let’s see if conditions change if we narrow down the time
> interval to 1940-1998:
> 
> (a) There are 20 documented falls for latitudes North and 2 for
> latitudes South in June.
> (b) There are 16 documented falls for latitudes North and 3 for
> latitudes South in December.
> 
> => These results favor the more densely populated areas of the northern
> hemisphere and may indicate the fact that more people are outside in
> summer. But the 20:2 and 16:3 ratios are so stunning that an explanation
> in O. Richard Norton’s RFS II may be helpful (I have his personal
> permission to quote from his book):
> 
> ‘Since most of these meteorite falls were observed in the Northern
> Hemisphere, these data must have been influenced by the Northern
> Hemisphere's winter season, when there are fewer people outside on cold
> winter nights. However, if the fall of meteorites is uniform throughout
> the year, then the number of reports during the spring and fall months
> should be essentially the same, but they are not. Most meteoriticists
> conclude that these curves are telling us something about the
> distribution of meteoroid bodies in space. There may indeed be a greater
> concentration of meteoroids along Earth's orbit during the Northern
> Hemisphere's summer months than during the winter months’ (O.R. Norton,
> RFS II, p. 57).
> 
> 2b) Meteorite falls in Jan : 76
>  Meteorite falls in Feb : 71
>  Meteorite falls in Mar : 60
>  Total: 207
> 
>  Meteorite falls in Apr : 99
>  Meteorite falls in May : 102
>  Meteorite falls in Jun : 109
>  Total: 310
> 
>  Meteorite falls in Jul : 100
>  Meteorite falls in Aug : 99
>  Meteorite falls in Sep : 95
>  Total: 294
> 
>  Meteorite falls in Oct : 86
>  Meteorite falls in Nov : 71
>  Meteorite falls in Dec : 67
>  Total: 224
> 
> Or closer to the 4 seasons of the year:
> 
> 2c) Meteorite falls in Dec : 67
>  Meteorite falls in Jan : 76
>  Meteorite falls in Feb : 71
>  Total Winter: 214
> 
>  Meteorite falls in Mar : 60
>  Meteorite falls in Apr : 99
>  Meteorite falls in May : 102
>  Total Spring: 261
> 
>  Meteorite falls in Jun : 109
>  Meteorite falls in Jul : 100
>  Meteorite falls in Aug : 99
>  Total Summer: 308
> 
>  Meteorite falls in Sep : 95
>  Meteorite falls in Oct : 86
>  Meteorite falls in Nov : 71
>  Total Fall: 252
> 
> So we have:
> 
> 060 falls for Mar but 95 for Sep
> 099 falls for Apr but 86 for Oct
> 102 falls for May but 71 for Nov
> 
> The other way round still reveals a difference:
> 
> 060 falls for Mar but 71 for Sep
> 099 falls for Apr but 86 for Oct
> 102 falls for May but 95 for Nov
> 
> Last but not least, by 1998 people ‘Down Under’ (Hi, Joel!), in South
> America (Hi, Gianfranco) and South Africa will be as much on the
> meteorite alert during their summer months as people in the Northern
> hemisphere during theirs, and still there is an imbalance.
> 
> Sorry, if I drifted or rambled too far from the LYRIDS but, perhaps,
> some Keltic lyres or some Greek sirens have already put me under their
> spell.
> 
> Best wishes, Bernd
>