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Lyrids and Meteorite Fall Statistics

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