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Thread: Meteor speed

  1. #1
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    Meteor speed

    My book on micrometeorite collecting says that the determinant of how melted the micrometeorite is its speed (which sounds reasonable).
    It says the determinant of speed is how the meteoroid enters the atmosphere in relation to the Earth's rotation...against it is faster than "catching up".
    Well, OK, but how much? The most the rotational speed can be is about 1000 mph. The meteoroid has to enter the atmosphere at least at 25000 mph (escape velocity).
    And orbital of the Earth is over 66000 mph. The orbit of the meteoroid would seem to be the big thing.
    Am I right or is the author?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  2. #2
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    Quote Originally Posted by Tom Mazanec View Post
    My book on micrometeorite collecting says that the determinant of how melted the micrometeorite is its speed (which sounds reasonable).
    It says the determinant of speed is how the meteoroid enters the atmosphere in relation to the Earth's rotation...against it is faster than "catching up".
    Well, OK, but how much? The most the rotational speed can be is about 1000 mph. The meteoroid has to enter the atmosphere at least at 25000 mph (escape velocity).
    And orbital of the Earth is over 66000 mph. The orbit of the meteoroid would seem to be the big thing.
    Am I right or is the author?
    From the American Meteor Society:

    Meteors enter the atmosphere at speeds ranging from 11 km/sec (25,000 mph), to 72 km/sec (160,000 mph!). When the meteoroid collides with air molecules, its high level of kinetic energy rapidly ionizes and excites a long, thin column of atmospheric atoms along the meteoroidís path, creating a flash of light visible from the ground below. This column, or meteor trail, is usually less than 1 meter in diameter, but will be tens of kilometers long.

    The wide range in meteoroid speeds is caused partly by the fact that the Earth itself is traveling at about 30 km/sec (67,000 mph) as it revolves around the sun. On the evening side, or trailing edge of the Earth, meteoroids must catch up to the earthís atmosphere to cause a meteor, and tend to be slow. On the morning side, or leading edge of the earth, meteoroids can collide head-on with the atmosphere and tend to be fast.
    Makes me think the author is confusing rotational speed about the Earth's axis with the Earth's speed in its orbit around the Sun.

  3. #3
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    It would also depend on the speed and direction the meteoroid is traveling through space when it meets the earth.

    Fast moving meteor in a head on collision with the leading side of the Earth in its orbit = fast meteor. Slower moving meteor "catching up" with the trailing side of Earth in its orbit = slower meteor.

    The speed of the meteor relative to the Earth's rotational speed is a factor too.

    I wonder, given the same size and composition of 2 meteors, would a fast one be more likely to reach the surface without fully burning up in the atmosphere or would a slower one? Fast means more frictional heating, but less time to reach the ground, while slow means less friction but a longer time in the atmosphere.

  4. #4
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    Are we sure this isn't just a case of someone using the word "rotation" instead of "revolution"? People talk about "the Earth's rotation around the Sun" very frequently.

    Grant Hutchison

  5. #5
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    Isn't the fine dust meant to reach the ground unscathed, because it is decelerated gently in the very outer reaches of the atmosphere? Sure I read that somewhere.

  6. #6
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    The author had a picture showing the earth rotating around its axis, and three meteorites resulting...one head on melted into a sphere, one perpendicular semimelted into a lumpy blob and one catching up unmelted as a frackley mass.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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