100 Year Anniversary of the Tunguska Event

[PPI Brian]

You may not realize it, but today is an important anniversary. At approximately 7:17 am on June 30, 1908 something incredible happened: 

Tungus natives and Russian settlers in the hills northwest of Lake Baikal observed a huge fireball moving across the sky, nearly as bright as the Sun. A few minutes later, there was a flash that lit up half of the sky, followed by a shock wave that knocked people off their feet and broke windows up to 650 km (400 miles) away. The explosion registered on seismic stations across Eurasia, and produced fluctuations in atmospheric pressure strong enough to be detected by the recently invented barographs in Britain. Over the next few weeks, night skies over Europe and western Russia glowed brightly enough for people to read by. In the United States, the Smithsonian Astrophysical Observatory and the Mount Wilson Observatory observed a decrease in atmospheric transparency that lasted for several months.

Had the object responsible for the explosion hit the Earth a few hours later, it would have exploded over Europe --probably Scandinavia-- instead of the sparsely-populated Tunguska region, producing massive loss of human life and changing the course of human history forever.

Debate still rages as to the exact cause of the explosion. Was it a comet or a meteorite that exploded before impacting the earth? No crater was ever discovered, and the first expedition to the site did not arrive until 1927! (A few minor events delayed the expedition; World War I, The 1918-1919 influenza pandemic, The Russian Civil War to name a few...) What is known is that something exploded above the area with the force of a 15 megaton nuclear bomb, flattening over 800 square miles of trees in a "butterfly" air burst pattern. To put this in perspecitive, the atomic bomb dropped on Hiroshima on August 6, 1945, exploded with an energy of about 15 kilotons.

No worries, Dave; Tunguska may have been the most powerful impact event recorded in recent history, but it was not the only significant airburst event that Earth has endured. Several smaller events have been witnessed on an alarmingly regular basis, including several over Canada on separate occasions in the 1960s, and more recently, one over Italy in 1993, and two in 2002 over Russia and the Mediterranean Sea respectively. A close call occurred on 18 January 2000, when a five-metre diameter object exploded at an altitude of 20 kilmetres over Yukon in Canada causing a loud bang, a flash of light, a shower of fragments and an electromagnetic pulse that caused temporary loss of power transmission over the area.

So tonight, crack open that bottle of fine vodka you've been saving, raise your glass and toast the heavens... and hope that Dr. Shoemaker (codiscoverer of Shoemaker-Levy 9 that broke into twenty some-odd pieces and nuked Jupiter in 1994) knew what he was talking about; he said these events are exceptionally rare and may occur only once every few hundred years.

Here are a few links about the event.

Yahoo News:
http://news.yahoo.com/s/afp/20080629/sc_afp/sciencespaceimpacttunguska;_ylt=Aj3nee3eK0H_f.Up2QGhx4MPLBIF

Old Newreel Footage from Space.com:
http://www.space.com/php/video/player.php?video_id=071218-Tunguska2

Space.com article about the explosion:
http://www.space.com/news/080630-mm-tunguska-mystery.html

A 2007 article on the subject from Sandia National Laboratories:
http://www.sandia.gov/news/resources/releases/2007/asteroid.html

A Wikipedia article about the event, with a comforting table of similar air burst events that have been recorded over the last few years:
http://en.wikipedia.org/wiki/Tanguska_event

A NASA article about the January 2000 Yukon Blast:
http://science.nasa.gov/headlines/y2000/ast25jan_1.htm

Lest we forget the drama of Shoemaker-Levy 9:
http://en.wikipedia.org/wiki/Comet_Shoemaker-Levy_9

[MichaelF (FPIE)]

You know your going to give Dave nightmares with posts like this one.

It's not a matter of "if" the Earth will be hit by a large celestial object, it's a matter of "when."

[PPI Brian]

If that didn't give Dave nightmares, perhaps these will: A fireball was seen streaking over Los Angeles and seemed to fall toward the San Bernardino Mountains on July 1st. Here's a link to the LA Times article:

http://www.latimes.com/news/local/la-me-fireball2-2008jul02,0,5341752.story

And the theory that a comet or asteroid exploded over Canada during the last Ice Age 12,900 years ago and caused a wave of mass extinctions in North America which wiped out the Clovis culture has been given new life with the discovery of new evidence in Ohio and Indiana:

http://www.physorg.com/news134233301.html

[PPI Glenn]

I remember driving up to Griffith Observatory back in the 80's, right before sundown, and in the rear view mirror I saw a fireball coming from the west. I pretty much shit my pants and thought we were done for! Turns out it was part of a Russian rocket coming re-entering the atmosphere.

If that didn't give Dave nightmares, perhaps these will: A fireball was seen streaking over Los Angeles and seemed to fall toward the San Bernardino Mountains on July 1st. Here's a link to the LA Times article:

http://www.latimes.com/news/local/la-me-fireball2-2008jul02,0,5341752.story

And the theory that a comet or asteroid exploded over Canada during the last Ice Age 12,900 years ago and caused a wave of mass extinctions in North America which wiped out the Clovis culture has been given new life with the discovery of new evidence in Ohio and Indiana:

http://www.physorg.com/news134233301.html

[Kristen]

Mother nature reminding us who is in charge 

[PPI Brian]

Mother nature reminding us who is in charge 

She reminds us every clear night... if we would only take the time to look up at the sky. 

[Kristen]

Too much light and air pollution my friend.  But I agree with you 100%.

Mother nature reminding us who is in charge 

She reminds us every clear night... if we would only take the time to look up at the sky. 

[PPI Brian]

Thought this thread was worth resurrecting. Found this video featuring Carl Sagan from his Cosmos mini series where he discusses the Tanguska Event:

http://www.youtube.com/v/irVof7adq4s

http://www.youtube.com/v/4jgbw0aPxHs

[PPI Karl]

I remember, when I was in the 7th grade, the Tunguska incident was discussed in the Weekly Reader (which was a Catholic-approved science periodical for kids). In it they discussed that peculiar theory about a mini black hole colliding with the Earth!   Seriously, can you imagine?!  It just goes to show how much we were in denial even then about how prosaic asteroid events really are.

Thanks for posting these videos, Brian.  Love me some Sagan, and the clarity of mind he always brings to whatever topic he discusses.

[Shellshock]

WOW ! I never knew about this. Really amazing and actually a bit ...terrifying. O_o

[Gary]

WOW ! I never knew about this. Really amazing and actually a bit ...terrifying. O_o

I couldn't agree more.  I also had never heard of this event.  Or at least I wasn't listening! 

[PPI Brian]

If that kind of freaks you out, think about how the moon formed:

http://www.youtube.com/v/c0FCE4H0Dro

[Shellshock]

Oh My Gosh! Thats insanely AMAZING. Thats a trip.... crazy how they were able to figure out  how the moon was made.
I was always in awe of the moon , but even more so now! Ill never look at the moon in the same way again... Just Amazing, Amazing , Amazing.


And I Hope earth is meant to have just 1 moon. *Gulp* No sister moon in the near future please... :/    ::|

[PPI Tim]

Great video. It is what Shell said...Amazing. Thanks Brian.

[PPI Tracy]

Agreed!