[math-fun] meteorite lands near Chelyabinsk Russia, causes injuries
Allegedly over 900 sought medical help and a few hospitalized, but nobody killed. Supposedly Russian air defense systems shot it down (!). http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/ http://www.usatoday.com/story/news/world/2013/02/15/russia-meteorite/1921991...
Warren, where did you hear that Russian air defense systems shot it down? It exploded in the atmosphere just as meteoroids often do. --Dan From the USA Today article: ----- Deputy Prime Minister Dmitry Rogozin said the incident showed the need for leading world powers to develop a system to intercept objects falling from space. "At the moment, neither we nor the Americans have such technologies" to shoot down meteors or asteroids, he said, according to the Interfax news agency. ----- On 2013-02-15, at 11:55 AM, Warren Smith wrote:
Allegedly over 900 sought medical help and a few hospitalized, but nobody killed. Supposedly Russian air defense systems shot it down (!).
http://rt.com/news/meteorite-crash-urals-chelyabinsk-283/ http://www.usatoday.com/story/news/world/2013/02/15/russia-meteorite/1921991...
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The news story says: The regional Emergency Ministry denied previous unconfirmed reports by local media that the meteorite was shot by the military air defenses. The local newspaper Znak reported the meteorite was intercepted by an air defense unit at the Urzhumka settlement near Chelyabinsk. Quoting a source in the military, it wrote a missile salvo blew the meteorite to pieces at an altitude of 20 kilometers. Regnum news agency quoted a military source who claimed that the vapor condensation trail of the meteorite speaks to the fact that the meteorite was intercepted by air defenses. Witnesses said the explosion was so loud that it seemed like an earthquake and thunder had struck at the same time, and that there were huge trails of smoke across the sky. Others reported seeing burning objects fall to earth. On Fri, Feb 15, 2013 at 3:18 PM, Dan Asimov <dasimov@earthlink.net> wrote:
Warren, where did you hear that Russian air defense systems shot it down?
It exploded in the atmosphere just as meteoroids often do.
--Dan
From the USA Today article:
Deputy Prime Minister Dmitry Rogozin said the incident showed the need for leading world powers to develop a system to intercept objects falling from space.
"At the moment, neither we nor the Americans have such technologies" to shoot down meteors or asteroids, he said, according to the Interfax news agency. -----
On 2013-02-15, at 11:55 AM, Warren Smith wrote:
Allegedly over 900 sought medical help and a few hospitalized, but nobody killed. Supposedly Russian air defense systems shot it down (!).
http://www.usatoday.com/story/news/world/2013/02/15/russia-meteorite/1921991...
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The Russian Academy of Sciences estimates the meteor had a mass of 10,000 tons, entered atmosphere at speed 15 km/s and exploded when 30-50 km up. NASA estimated it was 17 meters diameter and 10,000 tons with an energy release equivalent to roughly 500 kilotons of TNT. Only a small fraction of this mass actually hit the ground, most must have vaporized. The fireball in the videos is very bright, substantially exceeding the sun for a short time; most of the damage was caused by the blast wave breaking glass, I saw a press estimate of a million sq.ft. of sheet glass destroyed. My belief is there is a threshold size, when the meteor's mass is about the same as the column of atmosphere including the meteor, and only meteors above this threshold survive to reach the ground. The NASA estimate exceeded my crude threshold by a factor about 5, which probably means "about the same" should be revised to "about 10 times"... but the threshold depends on what the meteor is made of and what angle it comes in at, and in this case the angle was fairly near horizontal. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
On 2/16/13, Warren Smith <warren.wds@gmail.com> wrote:
The Russian Academy of Sciences estimates the meteor had a mass of 10,000 tons, entered atmosphere at speed 15 km/s and exploded when 30-50 km up. NASA estimated it was 17 meters diameter and 10,000 tons with an energy release equivalent to roughly 500 kilotons of TNT.
--NASA got it wrong, since 500*kiloton = 2.1*10^15 joule = m*v^2 / 2 and with v=15 km/sec, we find m is at least 18666 tonnes ("at least" since not all energy released in the blast).
15 km/sec is rather leisurely for a meteor. Escape velocity (or falling from infinity) is ~11km/sec. Earth's orbital speed is ~30km/sec, and anything that approached from a random directiopn should have a similar speed. Rich ---- Quoting Warren Smith <warren.wds@gmail.com>:
On 2/16/13, Warren Smith <warren.wds@gmail.com> wrote:
The Russian Academy of Sciences estimates the meteor had a mass of 10,000 tons, entered atmosphere at speed 15 km/s and exploded when 30-50 km up. NASA estimated it was 17 meters diameter and 10,000 tons with an energy release equivalent to roughly 500 kilotons of TNT.
--NASA got it wrong, since 500*kiloton = 2.1*10^15 joule = m*v^2 / 2 and with v=15 km/sec, we find m is at least 18666 tonnes ("at least" since not all energy released in the blast).
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The NASA release statement is apparently based on calculations by Peter Brown of the University of Western Ontario. I notice that Warren applies the Russian speed estimate to the NASA energy release number but I would guess that Peter Brown elected to use his own number. If his speed was closer to 20 km/s, there is no issue. On Feb 16, 2013, at 3:13 PM, Warren Smith <warren.wds@gmail.com> wrote:
On 2/16/13, Warren Smith <warren.wds@gmail.com> wrote:
The Russian Academy of Sciences estimates the meteor had a mass of 10,000 tons, entered atmosphere at speed 15 km/s and exploded when 30-50 km up. NASA estimated it was 17 meters diameter and 10,000 tons with an energy release equivalent to roughly 500 kilotons of TNT.
--NASA got it wrong, since 500*kiloton = 2.1*10^15 joule = m*v^2 / 2 and with v=15 km/sec, we find m is at least 18666 tonnes ("at least" since not all energy released in the blast).
one article i saw in the paper made a distinction between the total energy (presumably, mv^2/2), and the amount of energy that reached the ground. the article said that most of the energy was absorbed by the atmosphere. in any case, video like this: http://www.guardian.co.uk/science/2013/feb/15/meteorite-explodes-over-russia... is pretty amazing! bob baillie --- Hans Havermann wrote:
The NASA release statement is apparently based on calculations by Peter Brown of the University of Western Ontario. I notice that Warren applies the Russian speed estimate to the NASA energy release number but I would guess that Peter Brown elected to use his own number. If his speed was closer to 20 km/s, there is no issue.
On Feb 16, 2013, at 3:13 PM, Warren Smith <warren.wds@gmail.com> wrote:
On 2/16/13, Warren Smith <warren.wds@gmail.com> wrote:
The Russian Academy of Sciences estimates the meteor had a mass of 10,000 tons, entered atmosphere at speed 15 km/s and exploded when 30-50 km up. NASA estimated it was 17 meters diameter and 10,000 tons with an energy release equivalent to roughly 500 kilotons of TNT. --NASA got it wrong, since 500*kiloton = 2.1*10^15 joule = m*v^2 / 2 and with v=15 km/sec, we find m is at least 18666 tonnes ("at least" since not all energy released in the blast).
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back when most of us were in high school, scientific american used to be a good magazine. but for what it's worth, here's an article on their website about the meteor: http://www.scientificamerican.com/article.cfm?id=chelyabinsk-fireball-astero...
The NASA release statement is apparently based on calculations by Peter Brown of the University of Western Ontario. I notice that Warren applies the Russian speed estimate to the NASA energy release number but I would guess that Peter Brown elected to use his own number. If his speed was closer to 20 km/s, there is no issue.
From a Sky & Telescope web article I can now confirm that, in Peter Brown's original analysis, the meteor's atmospheric entry speed was indeed 20 km/s ("typical for near-Earth asteroids"). I assume this did not change as he subsequently upped his mass and kinetic energy numbers.
participants (6)
-
Dan Asimov -
Hans Havermann -
Neil Sloane -
rcs＠xmission.com -
Robert Baillie -
Warren Smith