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Originally posted by DocEmrick
reply to post by JoeGuitar
Yeah, but they would have found an impact crater.
I'm trying to dig up all the fireball stories that happened this year.
I remember 2 or 3 of them making national news, one of them happened in Vegas if I recall correctly.
This is probably the same phenomena. I wouldn't rule out a meteor, but with no impact site, crash, or pieces found - this makes it similar to the other fireball cases. Now the question is, what the hell are these fireballs scorching through our atmosphere?
Originally posted by DocEmrick
In the Topix thread, someone brought up a good point.
If it was a fireball, this isn't the first. These have been occurring at increasing frequencies for the past year.
Get ready...
Originally posted by DocEmrick
reply to post by JoeGuitar
Yeah, but they would have found an impact crater.
I'm trying to dig up all the fireball stories that happened this year.
I remember 2 or 3 of them making national news, one of them happened in Vegas if I recall correctly.
This is probably the same phenomena. I wouldn't rule out a meteor, but with no impact site, crash, or pieces found - this makes it similar to the other fireball cases. Now the question is, what the hell are these fireballs scorching through our atmosphere?
Another destructive process which may operate against the fall of a meteorite is fragmentation of the meteoroid. The peak pressures these bodies can stand as derived from large bodies such as the recovered meteorites were found to be about 106N/m². This is much less than the crusting stress of about 108N/m² found in laboratory measurements. The reason may be in the earlier history of the meteorite parent bodies. Obviously, a very large fraction of meteoroids undergo a breakup when entering the atmosphere. This was visually observed in the past, but becomes very obvious from fireball photographs such as the Lost City images (McCrosky et al., 1971) and other meteor images (Babadzhanov, 1968)), as well as the video recordings taken of the Peekskill meteorite fall on October 9, 1992 (Brown et al., 1994).
How fast are meteorites traveling when they reach the ground?
Meteoroids enter the earth’s atmosphere at very high speeds, ranging from 11 km/sec to 72 km/sec (25,000 mph to 160,000 mph). However, similar to firing a bullet into water, the meteoroid will rapidly decelerate as it penetrates into increasingly denser portions of the atmosphere. This is especially true in the lower layers, since 90 % of the earth’s atmospheric mass lies below 12 km (7 miles / 39,000 ft) of height.
At the same time, the meteoroid will also rapidly lose mass due to ablation. In this process, the outer layer of the meteoroid is continuously vaporized and stripped away due to high speed collision with air molecules. Particles from dust size to a few kilograms mass are usually completely consumed in the atmosphere.
Due to atmospheric drag, most meteorites, ranging from a few kilograms up to about 8 tons (7,000 kg), will lose all of their cosmic velocity while still several miles up. At that point, called the retardation point, the meteorite begins to accelerate again, under the influence of the Earth’s gravity, at the familiar 9.8 meters per second squared. The meteorite then quickly reaches its terminal velocity of 200 to 400 miles per hour (90 to 180 meters per second). The terminal velocity occurs at the point where the acceleration due to gravity is exactly offset by the deceleration due to atmospheric drag.
Meteoroids of more than about 10 tons (9,000 kg) will retain a portion of their original speed, or cosmic velocity, all the way to the surface. A 10-ton meteroid entering the Earth’s atmosphere perpendicular to the surface will retain about 6% of its cosmic velocity on arrival at the surface. For example, if the meteoroid started at 25 miles per second (40 km/s) it would (if it survived its atmospheric passage intact) arrive at the surface still moving at 1.5 miles per second (2.4 km/s), packing (after considerable mass loss due to ablation) some 13 gigajoules of kinetic energy.
On the very large end of the scale, a meteoroid of 1000 tons (9 x 10^5 kg) would retain about 70% of its cosmic velocity, and bodies of over 100,000 tons or so will cut through the atmosphere as if it were not even there. Luckily, such events are extraordinarily rare.
All this speed in atmospheric flight puts great pressure on the body of a meteoroid. Larger meteoroids, particularly the stone variety, tend to break up between 7 and 17 miles (11 to 27 km) above the surface due to the forces induced by atmospheric drag, and perhaps also due to thermal stress. A meteoroid which disintegrates tends to immediately lose the balance of its cosmic velocity because of the lessened momentum of the remaining fragments. The fragments then fall on ballistic paths, arcing steeply toward the earth. The fragments will strike the earth in a roughly elliptical pattern (called a distribution, or dispersion ellipse) a few miles long, with the major axis of the ellipse being oriented in the same direction as the original track of the meteoroid. The larger fragments, because of their greater momentum, tend to impact further down the ellipse than the smaller ones. These types of falls account for the “showers of stones” that have been occasionally recorded in history. Additionally, if one meteorite is found in a particular area, the chances are favorable for there being others as well.
Originally posted by C.H.U.D.
Originally posted by DocEmrick
In the Topix thread, someone brought up a good point.
If it was a fireball, this isn't the first. These have been occurring at increasing frequencies for the past year.
Get ready...
Fireballs and meteorites have been occurring since long before you or I were around.
That said, there is no hard evidence that this was a fireball/meteorite, although it's certainly a good possibility.
Originally posted by JoeGuitar
I wouldn't go that far, exactly. According to a local meteorologist, there IS hard evidence to support a possible meteor strike. I am, in no way, an expert on this topic so I will yield to the rest of you:
www.wkyt.com...
12DEC2011 Warren Morrison Ontario,Canada 18:05 EST 4 or 5 seconds (approx.) Flash of bright light around me got my attention, first seen near zenith, moved vertically downwards, azimuth approximately 14 degrees, passed between alpha and beta Cassiopeiae, vanished at about altitude 50 degrees green, fragmenting, heard sound like thunder (a single boom) lasting one or two seconds, about three minutes later Bright enough to light up ground around me, perhaps as bright as half moon Broke into 5 to 10 pieces near end of trail Vertical descent from near zenith, azimuth about 14 degrees
After the explosion, lines appeared in the sky that some believed to be the contrails from an airplane.
“In the sky you could see like crisscrossed, like something had collided up there,” she said.
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