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On June 30, 1908, an extraordinary explosion occurred in the
Russian skies above modern-day Evenkia, Siberia, with repercussions that
continue to both fascinate and frustrate legitimate scientists and fringe
theorists alike. The so-called “Tunguska Event” or “Tunguska
Blast” (so named for the rural region near the Stony Tunguska River devastated
by the explosion) has since become famous among both astronomy aficionados and
conspiracy theorists, often blurring the line between science fiction and
science fact.

Let’s start, then, with the facts. Estimates vary on the
actual force of the Tunguska explosion—by a rather significant range of between
10 and 40 megatons. Like any good explosion, witnesses saw—and felt—a massive
fireball 60 kilometers away, and a shockwave caused recorded damage at even
greater distances, rattling some of the few seismographic sensors of the era in
Jena, Germany—more than 5,000 kilometers away.

Astronomers across Europe reported occluded sky conditions
consistent with some measure of dust fallout from a massive explosion. Rare noctilucent
(“night-shining”) clouds caused the skies above Europe to glow in the
nights following the blast, and meteorologists as far away as North America
reported unusual atmospheric pressure disturbances.

Given all this available data, the scientists of the day
should have been able to discern precisely what occurred in Tunguska. The only
problem is that no one outside of Siberia knew that anything had happened in Siberia, because the
region was so sparsely populated—and the political climate so chaotic—that word
of the blast didn’t immediately travel to the outside world.

Thanks to World War I and the Russian Revolution, a formal
investigation of the Tunguska Blast didn’t occur until 1927—almost two decades
after the fact.

When mineralogist Leonid Kulik finally began the
investigation, he went in search of an assumed meteorite impact. However, Kulik
was shocked to discover a region of trees still lying flat from the explosion—but
no impact crater.

This was something different, and unexplained, and only murky
facts exist to help clear the picture. It’s little wonder that the Tunguska
Event immediately became the subject of speculation—and from there, science
fiction took hold.


Who was the first known science-fiction writer to
fictionalize a possible explanation of the famous (and infamously unexplained)
“Tunguska Blast” of 1908?

That dubious honor goes to the all-but-unheard-of Soviet
engineer-turned-writer Aleksander Kazantsev, who advanced the notion that a
nuclear-powered Martian spacecraft exploded above Tunguska in his 1946 sci-fi
story. The inspiration for Kazantsev’s story was the engineer’s own
observations of the Hiroshima fallout in 1945, where he noted the striking
similarities between the felled trees of Tunguska and the flattened buildings
of the Japanese damage swath.

While it was the nuclear angle that brought Kazantsev’s
story some notice in the 1940s, it’s the notion of an above-ground explosion
that’s kept it in discussions ever since. The theory of an airborne explosion
explained the lack of an impact crater.

Moreover, when the Kulik expedition finally reached the
Tunguska blast epicenter in 1927, the mineralogist noted a group of trees at
the center of the damage area that remained standing straight up, while everything
around them lay pressed flat in an expansive butterfly-wing pattern.

These trees were likely directly beneath the aerial
explosion, with the downward force holding them in place, rather than flattening
them. All other speculations aside, an airborne detonation is perhaps the sole
aspect of the Tunguska Event upon which all parties can agree.

While conspiracy theorists still hold to many wild
explanations for the Tunguska Event—including the explosion of an alien
spacecraft—scientists have largely divided into two camps of theories: the
comet or the meteorite.

Studies have found gaseous traces of nickel and iridium in
the geological record that almost certainly indicates the detonation of an
extraterrestrial object above Tunguska at the place and time in question, but a
lack of corroborative geological evidence has left many astronomers and
physicists at a loss to decide between the explosion of an icy comet nucleus or
the total incineration of a conventional stony asteroid.

As for Kazantsev, science has embraced his aerial
suppositions, even if the world has all but forgotten him and his story. Still,
if imitation is the sincerest form of flattery, Kazantsev could take heart: In 1951,
a far more famous sci-fi scribe—Stanislaw Lem—suggested that the Tunguska blast
was the fallout from a spacecraft explosion, but Lem’s space travelers were
from Venus.

The Quibble of the Week

If you uncover a questionable fact or debatable aspect of
this week’s Geek Trivia, just post it in the discussion area of the article.
Every week, yours truly will choose the best post from the assembled masses and
discuss it in the next edition of Geek Trivia.

This week, we have the rare quibble of a quibble, with a
reader disputing The Quibble of the Week component from the Nov. 3 edition of
Geek Trivia, “Pretty
as a pixel.”
Here’s how TechRepublic member D.ajit explained the issue.

“My quibble is about the quibble [that] says that 10
MHz is supersonic. Supersonic always means faster than the speed of sound, and
subsonic means below. Sound frequencies above the human threshold of hearing
are… ultrasonic. Those below the lower threshold are correctly called ‘subsonic
frequencies’—and not just subsonic.”

The Trivia Geek, also
known as Jay Garmon, is a former advertising copywriter and Web developer who’s
duped TechRepublic into underwriting his affinity for movies, sci-fi, comic
books, technology, and all things geekish or subcultural.