Drawing of the split comet Biela,
from Amedee Guillemin's The Heavens (1868).
The Chicago Fire (2)
Where was Comet Biela?
A strange thing happened to comet Biela in 1845. The nucleus of the comet split into
two partners. The “smaller” comet (lower left in the picture above),
subsequently became more active and brighter than the larger. And
that was only the beginning.
In 1883, twelve years after
the Chicago fire, Ignatius Donnelly published a widely read book,
Ragnarok: the Rain of Fire and Gravel. Though the book
dealt primarily with the evidence for cometary disasters in ancient
times, Donnelly suggested that the Chicago fire provided a small
glimpse of the terror experienced by our earlier ancestors. “There
is reason to believe that the present generation has
passed through the gaseous prolongation of a comet's tail, and that
hundreds of human beings lost their lives”.
Reflecting on the
simultaneous events around Lake Michigan on the evening of October
8, 1871, Donnelly posed the underlying mystery: “At that hour, half
past nine o'clock in the evening, at apparently the same moment, at
points hundreds of kilometers apart, in three different states,
Wisconsin, Michigan, and Illinois, fires of the most peculiar and
devastating kind broke out, so far as we know, by spontaneous
combustion”. (We take up the historic testimony cited by Donnelly
and others in tomorrow’s “Picture of the Day”).
Donnelly believed he could
identify the cause of the devastation. He said it was Comet Biela, a
comet that captured attention from astronomers in 1826, returned for
a few predictable visits, broke into two nuclei, and then disappeared.
The comet was named after
Austrian officer W. von Biela, who observed the body in February
1826. By following the path of Biela, the French astronomer
Marie-Charles-Théodore de Damoiseau estimated the time of its
return. He said the comet would cross the orbit of the Earth about
one month ahead of our planet’s arrival at the same spot.
Donnelly does not mention
that ten days after Biela’s announcement, a French astronomer John
Felix Adolphe Gambart also sighted the comet. Both Biela and Gambert
calculated the orbit, recognizing that earlier comet apparitions in
1772 and 1805 were the same object that appeared in 1826. And
Gambert, along with other astronomers, predicted that the comet
would strike the earth on its return, which he
projected for October 29, 1832.
Damoiseau’s prediction was
correct. Earth missed the comet by about a month.
On its anticipated 1846
return, Biela was first sighted in late 1845 as it moved toward
perihelion (its closest approach to the Sun), astronomers were
surprised to see that the head of the comet had acquired a faint
satellite. It had split in two (picture above), something we now
know to be fairly common for comets, but still mysterious to
cometologists. In 1845, the event seemed unprecedented. As noted by
Carl Sagan and Nancy Druyan in their book Comet, “the
finding was so bizarre that the first astronomer to note this
twinning dismissed it as some internal reflection in his telescope”.
In Robert Chapman’s and John
Brandt’s The Comet Book certain details of Biela’s
return are fascinating. The discovery of a partner occurred on
January 13, 1846, when “a faint satellite comet was observed a small
distance from the main comet”. Two tails were seen parallel to each
other. “Over the next month the fainter of the two comets increased
in brightness and finally became brighter than the ‘main’ comet. The
situation then reversed and the main comet became the brighter one
again. In addition, the main comet grew a second tail and a
luminous bridge of material joined the two comets” [emphasis
ours]. At this time the two nuclei were apart an estimated
250,000 kilometers, about two thirds of the distance separating Earth and the Moon.
Donnelly’s account at this
point diverges from the history told by Chapman and Brandt. As
Donnelly tells it, “In 1852, 1859, and 1866, the comet should
have returned, but it did not”. But Chapman and Brandt—prominent
figures at NASA’s Goddard Space Flight Center at the time of their
book’s publication—say that the twin comet-heads did indeed appear
at the appointed time in 1852. This reappearance is, in fact, well
documented. And one detail in Chapman’s and Brandt’s account rarely
shows up in standard discussions of cometology:
“…Both comets returned at the predicted time,
though they were over 2 million kilometers apart
[emphasis ours]. Once again the two comets took turns as the
brighter of the pair. On at least one occasion a bright jet
was seen between the two heads” [emphasis ours].
Though Sagan and Druyan
report the splitting of Biela, they do not mention the jet, an event
for which the standard view of comets has no theoretical reference.
The rest of Donnelly’s discussion of Biela is in
general agreement with the summary by Chapman and Brandt. Amazingly,
and with the aid of a startling and unpredicted meteor shower on
November 27, 1872, Professor W. Klinkerfues of Berlin, calculated
the trajectories of the meteoric falls, concluding that they were
the remains of the comet. This, in turn led him to send instructions
to Norman Pogson, Government Astronomer at the Madras Observatory in
India (far enough south to allow a good view). Pogson’s answer to
Klinkerfues, dated December 6, said he “found Biela immediately” on
the first clearing of the sky, and on the second day he saw it
again. It showed no tail, he said.
As Chapman and Brandt put it, this was either an
“incredible coincidence”, or it was the actual last view of the comet.
The spectacular meteor shower that inspired
Klinkerfues to identify it with Biela has long since become an
annual event—sort of—called the Andromedids. And astronomers do not
hesitate to connect the shower to Biela. Each year the Earth passes
through the remains of the comet, but with widely varying
consequences. And the effect today is trivial by comparison with the
November 1872 occurrence. Today the shower peaks around
mid-November, averaging less than three meteors per hour—hardly
deserving the title “shower”. On the night of November 27, 1872,
however, records show several thousand meteors per hour—a
direct and obvious link to the disintegration of the comet.
It remains to be asked, then, whether the
fragmentation of Biela, a comet on a path intersecting the orbit of
the Earth, and predicted by some astronomers to collide
with the Earth in 1832, might have been the source of the “great
conflagration” in 1871. The comet had split at least 25 years
earlier (the 1846 appearance), and the two partners had separated by
more than 2 million kilometers by 1852. So whether or not Klinkerfues
observed Biela after the spectacular shower of November 1872, we
know he did not report seeing two bodies. Hence, at
least one of the partners intersecting Earth’s path had presumably
already disintegrated entirely, leaving the possibility that on a
subsequent orbit the Earth moved into debris left by the body.
The facts on the Andromedids, including their
erratic occurrence over the years and the obvious dispersal and
depletion of the cometary debris over a century and a half, cannot
give us a definitive answer to Donnelly’s views on Biela. But as for
plausibility, the answer is definitive. Many facts are
consistent with the interpretation, and there are no facts that
exclude the interpretation.
Of course, it is not necessary to identify an
intruder, in order to see the evidence of an intrusion. No one
questions the exploding
Tunguska comet, asteroid or meteor on
the basis that astronomers cannot identify the incoming object.
But of all the scientific details about comet Biela, perhaps none
stands out more dramatically than the fact almost never mentioned—a
jet forming between the two nuclear
fragments when they were 2 million kilometers apart. In the purely
gravitational and mechanical terms that astronomers have sought to
apply to comets, this jet is inconceivable. But when we remember how
inconsequential is gravity in the presence of the electric force,
the improbability disappears.
In fact, the jet is a clue more vital by far than the popular
“scientific” commentary on Donnelly’s hypothesis. By directing our
attention to the electrical nature of comets, it also invites us to
look again at the historic testimony, with an eye to details long
unnoticed or forgotten.
The Chicago Fire (3): Human Testimony Reconsidered