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Lightning in the sky

  1. Jul 13, 2008 #1
    i am tuan anh, i am from vietnam
    very happy when join this forums
    i have one question
    when i see the lightning in the sky i don't hear nothing in it
    i don't understand why
    please help me
    thanks
     
  2. jcsd
  3. Jul 13, 2008 #2

    DaveC426913

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    Hello Tuan, and welcome!

    While lighting travels to you at the speed of light (pretty much instantly), thunder travels to you only at the speed of sound (1000feet per second).

    If the lightning occurs 5 miles away, it will 25 seconds before you hear the thunder.

    You can use this to tell how far away a storm is. When you see a flash of lightning, start counting off seconds. One...two...three... If you get to 'five', the lightning strike was a mile away. Ten seconds means it was two miles away, and so on.



    Additonally, if lightning is occurring far enough away, the thunder can be completely lost in powerful wind currents, and may simply be too weak to reach you.
     
  4. Jul 14, 2008 #3

    Borek

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    I think that's not what the question asks about. From my observations, it happens quite often, that lightning that strikes inside of the clouds is visible (well, not lightning is visible, but the flash inside of the colud), but no matter how long you wait you never hear it. I know the effect and it makes me wonder why is that so as well. Doesn't look like it is because it happened too far from me, as other similar lightnings (in terms of flash brightness measured by eye, so I can be wrong) striking during the same thunderstorm are loud.
     
  5. Jul 14, 2008 #4
    yeah that kind of thing is called heat lightning. It has no noticable sound and is just in the clowds (if i understand what you are asking?)

    its caused by heat and clowds condensing. See, the heat that is rising from the ground swells the clowds that are cooling down during the night and friction crates a flash of light. So basicly its different from thunder (which you hear at closer range).

    what you have to understand is that there is a difference from thunder (what you see and hear louder) and lightning (what you just see [but can hear if very close sometimes] and can be many different colours).

    P.S. Welcome mate! :)
     
  6. Jul 14, 2008 #5
    I see obviously voltaic fire hurl in the sky
    this is a argillous jet
     
  7. Jul 14, 2008 #6

    DaveC426913

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    I'm afraid you've lost me.

    'argillous' means clay-like.
    I don't know what 'voltaic fire' is.
     
  8. Jul 14, 2008 #7
    sorry
    rewrite "I sure I saw lightning in the sky. it is very legible. I think it is not far and I do not think the thunder can vanish"
     
  9. Jul 14, 2008 #8

    DaveC426913

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    We call that heat lightning. This Wiki article describes other reasons why you might not hear the thunder.
     
  10. Jul 14, 2008 #9

    tiny-tim

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    Welcome to PF!

    Yes, welcome tuan anh! :smile:

    You can read about heat lightning in http://en.wikipedia.org/wiki/Heat_lightning :smile:
     
  11. Jul 14, 2008 #10

    DaveC426913

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  12. Jul 14, 2008 #11

    tiny-tim

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    … oops!

    ooh … sorry …

    I got "heat lightning" from kateman's post.

    I didn't realise you had linked to the same thing. :redface:

    (that's why I usually paste the whole url when I link to wiki :wink:)
     
  13. Jul 14, 2008 #12
    thank you vert much
     
  14. Jul 15, 2008 #13
    Re: Welcome to PF!

    haha that made me smile :smile:
     
  15. Jul 16, 2008 #14
    I am not an expert on this subject, but I will offer my thoughts anyway. You never "hear" lightning. You only hear the sound of the ambient air (or other media) being disturbed by the heat generated by the lightning as it passes through the air (or other media).

    It is my understanding that some lightning arcs are from sky to ground and some arcs occur between different points of electrical charge within the air. If an arc occurs over a very short distance, then you could see a very bright arc flash but not have very much of the medium in which the arc propagates being disturbed by the associated heat. This short distance arc wouldn't create as much sound as a long distance arc.

    That's my guess, for what it's worth.
     
  16. Jul 17, 2008 #15
    you never hear ninja's either, but they're just as deadly as lightning

    what do you mean? all energy flows from positive to negative. current goes from positive to negative. gravity goes from positive (higher) to negavtive (lower). magnitism goes from positive (north) to negative (south).

    there is no difference in current travel from the ground to sky or sky to sky lightning/thunder strikes
     
  17. Jul 17, 2008 #16

    DaveC426913

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    That is one of the most bizarre generalized inferences I've ever heard.

    Not one of the those statements is true.


    I think he's saying that sky-to-ground requires a huge potential, whereas sky-to-sky requires only a small potential. Even a small flash will still be easily visible but the thunder will be dramatically reduced.
     
  18. Jul 17, 2008 #17
    Thank you Dave, for clarifying my position. I suspect that kateman's intent was to be playful? Ninjas? Really?

    While classical electronic theory has postulated current flow from a "positive" to "negative" potential (this is reflected in some standard electronic symbols), with the exception of "hole current" in semiconductors, electrical current flow tends to consist of electrons moving from a negative to positive potential.
     
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