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Record Meteorite Hits Norway
equex256 writes "Early Wednesday morning, a meteorite streaked across the sky in northern Norway, near Finland and Russia. A witness (Article in Norwegian) went up the mountain to where it hit and reported seeing large boulders that had fallen out of the mountainside, along with many broken trees. Norwegian astronomer Knut Jørgen Røed Ødegaard told Aftenposten, Norway's largest newspaper, that he would compare the explosive force of the impact with the Hiroshima bomb. This meteorite is suspected to be much larger than the 90-kilo (198-pound) meteorite which hit Alta in 1904, previously recognized as the largest to hit Norway. From the article: 'Røed Ødegaard said the meteorite was visible to an area of several hundred kilometers despite the brightness of the midnight sunlit summer sky. The meteorite hit a mountainside in Reisadalen in North Troms.'"
Was it as big as the one that (supposedly) fell at Tunguska? Although I'm still pretty sure that was caused by dark matter or a UFO or something.
Of course the meteor would not have had any noteworthy radioactivity and was not in a populated area. I don't remember exactly how often it's estimated to happen and I can't find any sources, but meteors of this size hit the earth a lot more often than most people realize...something like between once a year and once a decade. The comparison to Hiroshima really is about the energy of the impact, not the destructiveness. Little boy had a yield equivalent to approximately 15,000 tons of TNT.
Whenever the topic of meteors comes up, someone has to post a link to the University of Arizona impact effects calculator. Play with the numbers, see if you can destroy the earth.
Also worth checking out along the Lucifer's hammer line of thought is How to Destroy the Earth
I tried a quick reverse engineering of the meteor with the calculator. An iron meteor 4.5 meters in diameter moving 20 km/s hitting crystalline rock at 45 degrees will have a yield of 18 kilotons...slightly higher than the atomic bomb detonated over Hiroshima. The average interval of an impact of this size on earth is about once every 5 years. Most go largely unnoticed. The earth is a big place.
I wonder (1) how recent and what resolution Google Earth's latest imagery is, and (2) can we get them to take another shot ASAP and compare them?
Actually, I saw a paper presented back in the late 90's that fairly convincingly made the case for a mostly iron meteor. The author's contention was that the object slowed due to air resistance, it would heat up. As is heated, the metal would have softenned. As it softenned, the metal would start to pancake like a dum-dum bullet. As it pancakes, its air resistance increases, causing it to slow down even more and heat up even faster, causing it to pancake even more... until you get an airbirst at an altitude with on the order of magnitude suggested by the tree angles at Tunguska. If you acept his hypothesis about the meteor's composition, there were no major contradictions in the evidence.
Perhaps you're mistaking entry mass for landing mass?
A meteorite's surface vapourizes from reentry heat when it enters the atmosphere. If the meteorite is small enough, the entire object will be plasma long before it hits the ground; it takes a large or dense object to survive reentry, and even then much of it's mass is lost.
That doesn't however mean that it disperses. There is at least one theory that a meteorite could hit the ground as a ball of plasma with a solid core, due to the surrounding air pressure preventing the superheated surface from dispersing even after it vapourizes. I seem to recall seeing this put forward for the Tunguska blast in Siberia. IANA Astrophysicist, so I don't know how fast the object would need to be moving, or how large it would have to be initially, to produce this effect.
If that did happen, what would you use for your calculations? The mass of the meteorite wouldn't all be solid when it hit, and whatever material wasn't vapourized by descent or on impact would only make up a fraction of the mass present during the impact. The core might be 90kg, or 300kg, or whatever, but using that figure to calculated the speed the object on impact would be incorrect. You'd need to mass of the meteorite on reentry, minus whatever mass bled off during descent.
However, I would agree that comparing the impact to an atomic bomb blast is silly. It's like comparing a firecracker explosion to a bullet impact - yes, you can say that one has X amount of energy and the other has Y (and you could probably calculate this by measuring the gunpowder present in each, and determining how much energy you get from burning it), but that comparison doesn't actually tell you anything useful, since the energy is applied in a very different fashion. It's comparing apples to oranges.
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