Hi,
Regarding your #2, the "Siberian guy" was named
Semenov. He was at a trading station (Vanavara?), sitting
on the front porch facing the impact site. His (white) shirt
did NOT catch fire. When the light and shock from the
impact reached him, he was rocked back in the chair
before he leapt up slapping at his shirt, which he was
sure was "on fire," based on the (infrared) intensity
he felt. The shirt was not on fire but was very warm.
His face felt like he had "looked into a stove," painfully
hot, but was not burned nor reddened. Since the U. S.
Navy used infrared light on volunteers to establish the
pain scale used by doctors today (bad kidney stone wins
with a 10), we can closely estimate the infrared flux he
received at that distance, a valuable clue to the total energy
of the blast. (The distance was 43 miles, but you have to
double-check all reported distances in Tunguska reports,
as the Russians actually measured distances at that time
in "versts," not identical to a Western mile, but usually
translated to English by the word "mile.")
Tungus herders at 24-25 miles from the blast suffered
deaths and injuries, almost entirely from blast effects. The
forest was eradicated, burnt and flattened out to 15 miles
(except where sheltered by the topography); herds and
herders at 15-18 miles were never seen again.
At fifteen miles your cotton shirt would have caught fire;
at ten miles, your hair and exposed skin would have been
burned and blistered; at five to seven miles... yes, your skin
would be burned, but the shock wave would have stripped
it right off your body, so... sort of irrelevant.
Tunguska stories are like fish stories; they improve with
every telling.
Sterling K. Webb
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----- Original Message -----
From: "JoshuaTreeMuseum" <[email protected]>
To: <[email protected]>
Sent: Tuesday, April 21, 2009 12:33 PM
Subject: [meteorite-list] Vancouver Meteorite Boom Friday
I have two problems with this story:
1.) Wouldn't it have to be a really really bright bolide to see the
flash while inside a vehicle under a thick sleeping blanket with your
eyes closed?
2.) The 1908 Siberian guy: From 60 Kilometers away, would your shirt
really catch on fire? If it did would it burn before the concussion
blast? If your shirt caught fire, wouldn't all flammables nearby also
catch fire resulting in a general conflagration? Wouldn't this have
been mentioned in the story?
A mysterious "boom" that resounded across Vancouver early Friday may
have been an extraterrestrial wake-up call, theorizes a geophysicist
with the U.S. Geological Survey in Vancouver.
"I can't think of any other explanation, other than a fairly
substantial gravel quarry explosion," said Jeff Wynn, research
geophysicist with the Cascades Volcano Observatory.
Local gravel quarries reported no activity, especially at 6 a.m.
Several online readers last week offered theories about the noise,
which some reported rattling windows and spooking animals. But, in a
story on Saturday, experts ruled out some of the obvious theories. It
wasn't a thunderclap. It wasn't a volcanic eruption. As far as
emergency managers know, nothing exploded on the ground.
Wynn said Monday he's reasonably confident that it was a relatively
large meteorite known as a bolide blowing apart in the atmosphere
miles above Vancouver. He said these arrivals are surprisingly common,
though normally not in such a densely populated urban area where it's
experienced by so many people.
People generally reported the noise in an area of no more than about
10 miles, from west Vancouver to Hazel Dell and Orchards.
"A relatively small object could do that," Wynn said. The object was
probably "on the order of maybe a foot when it hit the upper
atmosphere. It was probably pretty close to vertical" to be heard in
such a confined area.
If it was any bigger?
"Portland wouldn't be here," he said.
Wynn personally studied the landscape impacted by an iron-nickel
object that crashed down in a remote area of Saudi Arabia in 1863. It
had "all the effects of a Hiroshima-scale atom bomb except one: no
radiation," he wrote in an e-mail.
The objects enter our atmosphere at mind-bending speed - 7 to 25
kilometers a second, Wynn said - which causes air to stack up in front
and a vacuum behind. When the bolide breaks apart, its
now-exponentially larger surface area creates a blindingly bright
flash and a sonic boom.
Wynn recalled witnessing one by happenstance while in the midst of a
fierce sandstorm on the Arabian Peninsula in 1994.
He had bundled up against the storm inside his Land Cruiser, pulled a
thick sleeping bag over his head and had his eyes shut. The flash
penetrated the total darkness.
Depending on the size, composition and angle of entry, space rocks can
do worse than create a loud noise or an interesting flash.
A bolide that detonated over the Siberian Taiga on June 30, 1908,
leveled a forest the size of Rhode Island, Wynn said. Sixty kilometers
south of the detonation point, a man in a remote trading post was
assembling barrels with his back to the action.
"The first thing he knew, the back of his homespun wool shirt caught
on fire," Wynn said. "As he pulled the shirt off, the concussion blast
hit him and knocked him end over tea kettle."
Wynn said the man's wife, spotting her husband laying half-naked and
unconscious at the base of a tree, lugged him inside their cabin and
nursed him back to health.
In the case of the Vancouver boom, he said, the object had to be much
smaller and composed of stony material rather than dense iron.
"If people find pieces of this thing on the ground, it will have a
burned and pitted look," he said.
Wynn downplayed the chance that it was a sonic boom from an
early-morning military operation, both because a spokesman for the
Oregon Air National Guard discounted it and because the area affected
was more confined than what Wynn would expect from a sonic boom from
an aircraft.
"The idea that it would be a sonic boom from a military aircraft is
pretty darn small now," he said. "It's a huge waste of energy, and
you'd only do that if you're trying to chase someone down and shoot
them."
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