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Why don't shooting stars make a noise?

  1. Jan 28, 2012 #1
    Pretty self explainable.

    Why do they not create a sonic boom when they enter Earths atmosphere
     
  2. jcsd
  3. Jan 28, 2012 #2

    davenn

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    How do you know they dont ?

    I would suspect that they do, considering they are travelling at 20km/s or greater
    many times the speed of sound :)

    the absence of hearing a sonic boom is not proof of the absence of a boom.
    It just means you are too far away from the object to hear it. The majority of the meteors
    you see burning up in the atmosphere are doing so at 50 - 75km altitude.

    Sound doesnt travel very far through the atmosphere. Even the massive booms of thunder
    only travel ~ 15 km max before they die out

    cheers
    Dave
     
  4. Jan 28, 2012 #3
    interesting.
    How do you know that they do?

    Not saying i don't believe you, just curious.
     
  5. Jan 28, 2012 #4

    DaveC426913

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    Some meteorites have indeed been observed with an accompanying sound.
     
  6. Jan 28, 2012 #5

    Pengwuino

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    Especially the ones that hit you.

    A sonic boom creates sound that is no different from any other sound. If someone set off an explosive 15km away from you, there's a good chance you won't hear it unless it's a very powerful explosion (not to imply that a sonic boom is an explosion).
     
  7. Jan 28, 2012 #6
    There seems to be another mechanism by which meteors can "make" noise as the ionized gas goes through the magnetic field it releases radio waves which can cause conductive metals on the ground to vibrate.

     
  8. Jan 28, 2012 #7

    Bobbywhy

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    Although meteors must generate sounds they pass through the atmosphere at very high velocity, as others here have already explained, it’s no surprise that we normally don’t hear it. Sound does not propagate in air for great distances. Both spherical spreading and absorption diminish the sound intensity. For absorption the following variables affect the distance sound can travel: Air Pressure, Ambient Air Temperature, Percent Relative Humidity, and Sound Frequency.

    Since thunder also generates sound, and that sound must propagate through our atmosphere to be heard, it may be useful to investigate the physics of thunder sound propagation. Here are two sources that describe this:

    1. Thunder is seldom heard beyond 10 miles (16 km) under ideal conditions. The sound of distant thunder has a characteristic low-pitched rumbling sound. Pitch, the degree of highness or lowness of a sound, is due to strong absorption and scattering of high-frequency components of the original sound waves, while the rumbling results from the fact that sound waves are emitted from different locations along the lightning channel, which lie at varying distances from a person. The longer the lightning channels, the longer the sound of thunder. Humans hear frequencies of thunder between 20-120 Hertz (Hz). However, there is a small amount, less than 10%, that is inaudible to humans produced from lightning, called infrasonic. Special listening devices are required to record these inaudible sounds.
    http://www.lightningsafety.com/nlsi_info/thunder2.html

    2. See the sections “Thunder sound propagation” at this site:
    http://en.wikibooks.org/wiki/Engineering_Acoustics/Thunder_acoustics

    Finally, here are some real examples of witnesses hearing the sound of a meteorite:

    3. "Sounds Associated with Witnessed Meteorite Falls"
    http://www.meteorites.com.au/odds&ends/sounds.html
     
  9. Jan 28, 2012 #8
    Just thought I'd add my own eye witness account. One sunny day I was walking across an open field when I happened to look up at just the right time to see a bright meteor streak across the sky. The head was orange and the tail was blue. Before it disappeared it split into two meteors. Then about 30 to 60 seconds after it disappeared I heard a sound very similar to thunder. It did not sound so much like a sonic boom, just more like thunder.
     
  10. Jan 28, 2012 #9

    davenn

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    That would be right and would be the same for a supersonic aircraft at a distance from you

    just the same with the thunder from a close compared to a more distant lightning strike.
    the close one a sharp loud crack, the more distant one a lower freq and longer rumble

    Dave
     
  11. Jan 28, 2012 #10

    DaveC426913

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    BTW, most meteors that we see tend to burn up very very high in the atmosphere, near the edge of space. The air is very tenuous up there - enough to create a shock and cause the meteor to burn up, but it carries sound poorly. So, not at all like thunder.
     
  12. Jan 30, 2012 #11
    The language of the Jaru people of Australia contains a word, "goolunmurru", that describes the sound and vibration of sonic booms from meteors or shooting stars.
     
  13. Jan 30, 2012 #12

    tony873004

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    I saw the Space Shuttle re-enter once. I heard the sonic boom. IIRC, the delay was several minutes.
     
  14. Feb 4, 2012 #13
    At 5 seconds a mile, a meteor sonic boom 50 miles above you (neglecting variation in SoS w/ altitude) is going to take 250 seconds to reach you. How many folks seeing that are going to realize they have to wait that long to have a chance to hear the thud?
     
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