Meteorites have been falling upon our planet for a long time—how long,
it is hard to say with accuracy. Up to now, no specimens certainly
identified as meteorites have been found in ancient rock layers.
Scientists have been able, however, to estimate the age of several
meteorite craters on the basis of the degree of weathering not only of
the crater rims, but also of the meteorites found around the craters.
Age estimates have also been based on the ages of fossils found in
silted-up crater interiors and on other related indirect evidence.
As we have already noted, the Canyon Diablo, Arizona, crater is thought
to be 20,000 to 70,000 years old. The Odessa, Texas, crater is at least
200,000 years old; and the Haviland (Brenham), Kansas, craters more than
600,000 years old. Clearly, meteorite falls have been occurring over a
very long period of earth history.
For many years, scientists have studied the distribution of recovered
meteorites around the world in an effort to find out whether there are
any places on the land surface of our globe where meteorites have fallen
in unusually large numbers.
The idea that any particular spot on the land surface of the earth might
in some way attract more meteorites to it than other locations seems
unreasonable because of the very nature of the target presented by our
planet to the meteorites wandering through space. Not only is the earth
in motion, but it is in very complicated motion. Our earth revolves
about a sun which is also in motion through space. At the same time, the
earth is rotating on its axis. A single point on the surface of the
earth therefore traces a very erratic path in space with the passage of
the years, and the likelihood that this particular point would be struck
by more than one meteorite (if indeed by one!) must be very small.
Studies have shown that the people of the earth have a great deal more
to do with “concentrations” of meteorite recoveries than anything else.
_Population density_ is the first important factor. Clearly, the more
people living in a given area, the higher the probability that a
meteorite fall will be seen and reported and that the fallen mass itself
will be recovered. A prime example is India, one of the most densely
populated regions of the world. Of the 102 meteorites recovered in that
country up to 1953, 97 were of witnessed fall. This extremely high
proportion of falls is undoubtedly due to the fact that for centuries
such an event could hardly have taken place in that country without
attracting the attention of large numbers of people. Apparently, the
majority of Indian meteorites have been recovered as they fell, for only
5 unwitnessed falls are recorded for that country.
On the other hand, from French West Africa only 5 falls and 3 finds have
been reported throughout an area slightly larger even than India’s. This
country thus provides an example of a sparsely populated region, in many
provinces of which a meteorite fall might pass unobserved, and a fallen
meteorite might remain undiscovered.
A second factor is the _degree of civilization_ reached by the
inhabitants of a particular area. Those regions of the world which have
been settled the longest and which have seen the development of the
higher cultures will be the most likely to support a populace that will
take an interest in and report the occurrences of natural events like
meteorite falls. Such a populace will also be more likely to bring
suspected meteorites to the attention of experts.
For example, up to 1953, 55 witnessed falls and 3 unwitnessed falls were
known from France, a country of relatively small area, but with a high
population density and an advanced degree of civilization. From the
whole vast area of Siberia, on the other hand, only 20 meteorite falls
and 23 finds have been reported during the same interval.
In the past, scientists have suggested that various natural forces, such
as the magnetic field of the earth or the attraction of high and massive
mountain ranges, might cause more meteorites to fall in one place than
another. But all available evidence indicates that this is not the case.
The fall of meteorites upon the earth has been and is a process that
shows no apparent pattern. Only “human” factors (like population density
and scientific interest in meteorites) can be considered as accounting
for any concentrations of meteorite falls in particular regions or
countries.
In historic times, the number of man-built structures (houses, barns,
hotels, office buildings, etc.) has increased tremendously. Such
structures have presented an ever-expanding target to hits by falling
meteorites. On pages 73, 74 is a listing of some of the meteorites that
have struck and damaged buildings during the last 150 years or so. The
items included in this list were chosen on the basis of interest,
authenticity, and concreteness of detail.
The stories of all these meteorite falls are exciting, but none more so,
perhaps, than that of the Beddgelert, North Wales, stone. This meteorite
fell in the small hours of the morning on September 21, 1949. Not many
people saw the fireball that accompanied its descent because of the
early hour (1:45 a.m.), but one of the few persons who happened to be
outside said that it resembled a huge rocket as it flashed across the
sky. He also reported that the appearance of the fireball nearly
frightened the swans in the local park to death, the birds fleeing in
all directions.
The manager of one of the hotels in Beddgelert simultaneously was
awakened from a sound sleep by the barking of his dog. This was an
unusual occurrence, and the man was surprised by it. While he was trying
to account for the dog’s peculiar behavior, he suddenly realized that
something quite out of the ordinary was happening outside. He heard a
series of unevenly spaced bangs that he later compared to “a naval
broadside.” But as the noise died away and nothing further happened, he
went back to sleep.
About noon on the next day, the manager’s wife went into the upstairs
lounge of the hotel, a room right under a part of the roof. She was
astonished to find plaster dust all over the floor. It had obviously
come from a jagged hole in the ceiling. And, on the floor, she found an
odd-looking dark stone.
Investigation showed that this stone had indeed fallen through the roof.
It had made a neat round hole in four overlapping thicknesses of slate,
shattered the underlying lath, made a dent in the lower edge of an
H-section iron girder, and had finally broken through the plaster
ceiling into the hotel’s upstairs lounge.
Although it was clear that the stone had come through the roof, the
hotel manager did not connect the event in any way with the peculiar
noises he had heard during the preceding night.
He tried to cut the stone on an emery wheel, but it was too hard.
That evening, an old miner in the hotel restaurant recognized the stone
as a meteorite. Many years before, he had visited a museum and had seen
specimens of meteorites on display there.
The slabs of slate penetrated by the meteorite would have provided good
evidence as to the speed of the cosmic missile at the time it struck the
roof. But, unfortunately, these appear to have been thrown away at the
time the roof was repaired. This fact is mentioned to show that
important scientific evidence is sometimes unwittingly destroyed before
investigators can get a chance to examine it.
Along with the rapid increase in the number of man-made buildings has,
of course, gone a simultaneous increase in the world’s population
itself. A person does not present as large a target to a falling
meteorite as a house or barn, but even so, if there were enough people
on the earth, it would seem that someone was bound to be hit sooner or
later.
[Illustration: G. W. SWINDEL, JR. PHOTO
COURTESY OF ALABAMA MUSEUM OF NATURAL HISTORY
The Sylacauga, Alabama, stone meteorite and the roof (note circle)
through which it plunged and struck a person.]
Actually, the first _authentic_ case of a person being struck by a
meteorite did not occur until November 30, 1954. Even then, the hit was
an indirect one. At Sylacauga, Alabama, a meteorite fell through the
roof of a house, went through the ceiling of the living room, struck the
top of a radio, and—bouncing in a 6-foot arc—hit the lady of the house,
who was taking a nap on the couch. Fortunately, nearly all of the energy
of the meteorite was spent by the time it struck the woman, and,
moreover, she was covered with two heavy quilts so that she was not
critically injured. But she did receive bruises serious enough to send
her to the hospital.
The instances just given show that a number of meteorites have struck
buildings and, in one case, a cosmic missile has hit a human being.
Nevertheless, such events are really quite rare. In fact, mathematical
calculations indicate that, on the average, we can expect one meteorite
to fall per township (36 square miles) per 1000 years. A rate like this
does not justify the loss of any sleep over the possibility that you
might some time be hit by a falling meteorite!