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Schroedinger's Rabbit
\ oo
\____|\mn / /_/ /\ \_\ - Free The Truman - / K-9/ \/_/ - Join www.chatty.net - /____/_____\ - Webmasters join www.BannerX.net - "Prigator" wrote in geopelia: A football-sized meteorite falling to earth would be spectacular and dangerous. The Earth is rotating and moving in an orbit around the sun, the sun is moving in an orbit with the galaxy, and our galaxy is moving in some direction. The meteor may have come from some other system somewhere, moving at its own velocity through space. It is not "falling" - it is intersecting. It may collide with Earth's atmosphere at Mach 30. Earth's gravity has little to do with it. Football sized meteors hit Earth all day. Stare up at the night sky for 15 minutes and you have a 50% chance of seeing a shooting star. For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) If astronauts on the moon saw one falling there, what would it look like? (No fiery trail of course and no sound.) Would there be a lot of heat on impact from kinetic energy? How close could they be to it to survive? Would a pressure wave knock them over without air? They might see it coming if the sun is on it. You see why the moon has so many craters? Craters within craters. It has been hit by big rocks and little rocks for a few billion years with no atmosphere to shield the surface. The astronauts would be in danger of flying shrapnel with a near miss. Right! Hence the frequency of shooting stars visibly burning up when reaching Earth. They come in clusters so its common to see 1 a minute! Herc |
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|-|erc wrote:
Football sized meteors hit Earth all day. Stare up at the night sky for 15 minutes and you have a 50% chance of seeing a shooting star. For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) Nitpicking: If they actually hit the ground, they're Meteorites - far more rare. The vast majority of what you're seeing in the night sky, while spectacular, never reaches the ground. Maybe you meant "hit the Earth's atmosphere" http://www.solarviews.com/eng/meteor.htm Most meteors are in the cm^3 range - most actually in the "grain of sand" range. One of the most thrilling shows is the summer (northern hemisphere) Perseid meteor shower. http://www.space.com/spacewatch/pers..._010731-1.html - regards |
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"TMG" One of the most thrilling shows is the summer (northern hemisphere) Perseid meteor shower. - regards Is it just me or has it been sucking lately? I seem to remember it being much livelier when I was a kid. Then again I grew up in a farming community with few city lights. Rob |
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Rob Duncan wrote:
"TMG" One of the most thrilling shows is the summer (northern hemisphere) Perseid meteor shower. - regards Is it just me or has it been sucking lately? I seem to remember it being much livelier when I was a kid. Then again I grew up in a farming community with few city lights. Rob They vary year to year - and "yes" a bit disappointing recently. It's also possible you're remembering the Leonids in the fall, which are more impressive - I've mixed up the two when "remembering as a kid". I suspect the biggest variable is the light pollution you didn't have as a youth. |
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"TMG" wrote in message ... Rob Duncan wrote: "TMG" One of the most thrilling shows is the summer (northern hemisphere) Perseid meteor shower. - regards Is it just me or has it been sucking lately? I seem to remember it being much livelier when I was a kid. Then again I grew up in a farming community with few city lights. Rob They vary year to year - and "yes" a bit disappointing recently. It's also possible you're remembering the Leonids in the fall, which are more impressive - I've mixed up the two when "remembering as a kid". I suspect the biggest variable is the light pollution you didn't have as a youth. Yah, I think youre right. Plus, I probably didnt even know the name of them as a child. I just remember our family laying out blankets next to the pool to lie on as we watched the "Star Show". Boy, I remember being thrilled as a child seeing all those meteors. And identifying satelites as they crossed our path of vision. Here, Portland, you have to drive 60 miles just to get away from the light polution. Rob |
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On 4/30/04 9:30 PM, in article
, "|-|erc" wrote: For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) How would something that was several feet across be football sized? Damn, I sure don't want to play on YOUR team! P |
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"Gistak" wrote in message
... On 4/30/04 9:30 PM, in article , "|-|erc" wrote: For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) How would something that was several feet across be football sized? Damn, I sure don't want to play on YOUR team! I believe his implication is that it would have to be several feet across when it entered the atmosphere in order to survive and hit the Earth as a "football sized" mass. Unfortunately, he is incorrect in his basic premise. Football sized and larger meteorites are not striking the Earth on a daily basis. The size of most meteors is somewhere between a grain of sand and a grain of rice. |
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"Kilolani" wrote in
wrote: For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) How would something that was several feet across be football sized? Damn, I sure don't want to play on YOUR team! I believe his implication is that it would have to be several feet across when it entered the atmosphere in order to survive and hit the Earth as a "football sized" mass. Unfortunately, he is incorrect in his basic premise. Football sized and larger meteorites are not striking the Earth on a daily basis. The size of most meteors is somewhere between a grain of sand and a grain of rice. You swapped from meteorite to meteor there. But the moon has millions of craters from reasonable sized collisions. Nothing is reaching Earths ground (regularly) so my implication was meteors are mostly *less* than football sized. Are you sure a grain of sand will ignite a visible trail across the sky? What is the smallest sized meteorite that will become a meteor and hit the ground? These occur on a decade or century basis, (second guesstimate). Herc |
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|-|erc wrote:
"Kilolani" wrote in wrote: For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) How would something that was several feet across be football sized? Damn, I sure don't want to play on YOUR team! I believe his implication is that it would have to be several feet across when it entered the atmosphere in order to survive and hit the Earth as a "football sized" mass. Unfortunately, he is incorrect in his basic premise. Football sized and larger meteorites are not striking the Earth on a daily basis. The size of most meteors is somewhere between a grain of sand and a grain of rice. You swapped from meteorite to meteor there. But the moon has millions of craters from reasonable sized collisions. Nothing is reaching Earths ground (regularly) so my implication was meteors are mostly *less* than football sized. The term meteorite means it gets all the way to the ground. Meteors do not. It's estimated that the earth gains ~10^8 kg per year from non-terrestrial infall. I'll leave it to the studious reader to calculate the impact on earth's gravity, tides, rotation, frame drag, etc. Are you sure a grain of sand will ignite a visible trail across the sky? Yes - plasma glow really lights up a dark night sky. Light pollution is why most of us don't see this as a common event. What is the smallest sized meteorite that will become a meteor and hit the ground? These occur on a decade or century basis, (second guesstimate). [other way around - 'ites are the ones that hit the ground] Depends on the angle of attack relative to the atmosphere. Dust floats in constantly. As to the strike size relative to the start size, there is a graph at: http://www.tulane.edu/~sanelson/geol204/impacts.htm that will give a good approximation. Herc regards |
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On 5/1/04 10:39 PM, in article
, "|-|erc" wrote: "Kilolani" wrote in wrote: For a football sized mass to reach the ground it would have to start out several feet across. (Guesstimate!) How would something that was several feet across be football sized? Damn, I sure don't want to play on YOUR team! I believe his implication is that it would have to be several feet across when it entered the atmosphere in order to survive and hit the Earth as a "football sized" mass. Unfortunately, he is incorrect in his basic premise. Football sized and larger meteorites are not striking the Earth on a daily basis. The size of most meteors is somewhere between a grain of sand and a grain of rice. You swapped from meteorite to meteor there. But the moon has millions of craters from reasonable sized collisions. Nothing is reaching Earths ground (regularly) so my implication was meteors are mostly *less* than football sized. Are you sure a grain of sand will ignite a visible trail across the sky? From space.com: -- Many shooting stars are produced by grit no larger than a grain of sand. Some of the more spectacular ones are pea-sized and the really stunning (but very rare) fireballs are the size of an orange or larger. http://www.space.com/scienceastronom...rs_000809.html -- What is the smallest sized meteorite that will become a meteor and hit the ground? A meteorite is a meteor that has struck earth's surface. P |
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