The Russian Chelyabinsk Meteor of Feb 2013

[Bill Ryan]

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Interesting article at http://edition.cnn.com/2013/02/27/wo...tml?hpt=hp_t3:

(extract, slightly summarized):

The big boom over Chelyabinsk on February 15 produced a wave of sound thousands of times lower than a piano's middle C -- far below the range of human hearing, according to the international agency that watches for nuclear bomb tests. The Comprehensive Test Ban Treaty Organization said that sound wave showed up on sensors from Greenland to Antarctica, making it the largest ever detected by its network.

Scientists then used that wave to calculate the size of the small asteroid that plunged to Earth, said Margaret Campbell-Brown, an astronomer at Canada's University of Western Ontario.

The duration of the wave -- about 32 seconds -- let scientists estimate the energy of the blast at between 450 and 500 kilotons, the size of about 30 early nuclear bombs

From there, Brown said, they could calculate the size of the fireball; and using an estimate of the meteor's speed from the numerous dashboard and mobile-phone cameras that captured the scene, it was "first-year physics" to figure out the approximate size and weight, she said.

The latest estimate is that the Chelyabinsk meteor was about 56 feet (17 meters) across, weighed more than 700,000 tons and was moving about 18 kilometers per second (40,000 mph) when it blew apart, she said.

[Ultima Thule]

Posted by Bill Ryan (here)
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Interesting article at http://edition.cnn.com/2013/02/27/wo...tml?hpt=hp_t3:

(extract, slightly summarized):

The big boom over Chelyabinsk on February 15 produced a wave of sound thousands of times lower than a piano's middle C -- far below the range of human hearing, according to the international agency that watches for nuclear bomb tests. The Comprehensive Test Ban Treaty Organization said that sound wave showed up on sensors from Greenland to Antarctica, making it the largest ever detected by its network.

Scientists then used that wave to calculate the size of the small asteroid that plunged to Earth, said Margaret Campbell-Brown, an astronomer at Canada's University of Western Ontario.

The duration of the wave -- about 32 seconds -- let scientists estimate the energy of the blast at between 450 and 500 kilotons, the size of about 30 early nuclear bombs

From there, Brown said, they could calculate the size of the fireball; and using an estimate of the meteor's speed from the numerous dashboard and mobile-phone cameras that captured the scene, it was "first-year physics" to figure out the approximate size and weight, she said.

The latest estimate is that the Chelyabinsk meteor was about 56 feet (17 meters) across, weighed more than 700,000 tons and was moving about 18 kilometers per second (40,000 mph) when it blew apart, she said.

The weight estimate has varied somewhat and the thing I can´t wrap my mind over is this:
17x17x17 meters(calculating it as a cube to at least not underestimate the dimensions) by 3500 kg/m3(the weight for quite dense rock) = 17195500kg, 17195,5 tons
Even when calculating at 8000 kg/m3(which according to wikipedia sources is for very rare materials) you get 39304000 kg, that is 39 304 tons, which is still lacking some 660000 tons from the estimate.

Am I getting something wrong in this calculation or is there just a difference in how numbers are expressed in different countries? Does the mentioned 700,000 tons mean 700 000 000 kilograms?

UT


EDIT: When looking at the original article the weight estimate is over 7,000 tons, not 700,000 tons, PROBLEM SOLVED, MOVE ALONG!

[Sunny-side-up]

I'm afraid my material brain has evolved away from maths (I'm no good at maths at all) Which is a mixed blessing. I am interested in seeing other calculations on this subject!

[Bill Ryan]

Some of the videos on this thread are no longer available, so I found this compendium. It's pretty impressive.

Go to 3:10 (and later) for the huge noise the thing made, and how much chaos ensued. 3,000 buildings were damaged, and 1,000 people injured. The atmospheric explosion was that of 300,000 tons of TNT... i.e. 20 Hiroshima bombs.

Source: https://youtube.com/watch?v=dpmXyJrs7iU