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I What causes thunder?

  1. Sep 22, 2018 #1
    The newest research information about what causes thunder makes more sense then the old theories.

    Tests show a capacitor bank discharged into a measured water volume turns into steam instantly producing 1800 volume of steam, producing more power than some explosives.

    A 300 mega watt capacitor bank was discharged into 2 tablespoons of water. The water turns to 1800 volumes of steam in less than 1/1000 of a second producing 36000 volumes of steam. Water has the explosive power of dynamite it blasted a hole through 3/4" plywood large enough to drop a basket ball through the hole. The explosion was so powerful that 99% of the wood from the hole was turned to dust.

    Thunder is directly proportional to the power of the lightning strike, the length of the lightning strike, and the amount of rain water in the path of the lightning strike. Lightning strikes are about 220,000,000 miles per hour (about 1/3 the speed of light). Lightning initial temperature is about 20,000 K to about 30,000 K. Several gallons of rain water can be turned to steam instantly producing a powerful explosion = to several 100 lbs of explosives.
     
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  3. Sep 22, 2018 #2

    anorlunda

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    Link please. We would like to see what you have been reading.



    Can we have lightning through dry air with little water content? If yes, is there no thunder? That should be testable.
     
  4. Sep 22, 2018 #3

    boneh3ad

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    You know, or it's the shock wave that occurs when lightning superheats air instantly.
     
  5. Sep 22, 2018 #4

    Charles Link

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    Water is a highly polar molecule which perhaps could have something to do with the heating process that occurs from the electric discharge, but I would like to see some calculations and experiments where someone has done a thorough study of the process.
     
  6. Sep 22, 2018 #5

    256bits

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    I get zapped by static electricity ( a small lightning strike ).
    I don't witness any steam being produced, yet I hear a noise.
     
  7. Sep 22, 2018 #6

    A.T.

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  8. Sep 22, 2018 #7

    anorlunda

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    Van de Graaf so what? I don't associate that crackle sound with thunder.
     
  9. Sep 23, 2018 #8
    YES, I don't associate spark sounds with thunder either. The sound of a spark is different than thunder. Oak Ridge National Lab TN has 10 Van de Graafs stacked to a height of 150 ft they can make sparks 150 ft long. If you watch the sparks at the observation window there is a loud snap sound from the sparks but no thunder.
     
  10. Sep 23, 2018 #9

    anorlunda

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    That's very cool. I would love to see that the next time I pass through Oak Ridge. Is it open to the public?

    p.s. 50 years ago I met Dr. Van de Graaf at High Voltage Engineering Co. on RT 128 near Boston. They were busily building accelerators to be use in the manufacture of heat shrinkable plastic film.
     
  11. Sep 23, 2018 #10

    davenn

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    I don't think I would agree with those comments
    we are talking about a huge difference in discharge size, voltage and surrounding conditions


    150 ft ??? peanuts !

    the avg lightning discharge is around 2km ... some a little shorter ~ 1km, many much longer upwards of 5km or so

    The very much higher voltages and currents and in the open air rather than strongly controlled lab conditions all add up to
    a major increase in the level of sound heard when the air is converted to plasma.

    OK found a comment

    https://en.m.wikipedia.org/wiki/Lightning#Thunder

    ThunderEdit
    Main article: Thunder
    Because the electrostatic discharge of terrestrial lightning superheats the air to plasma temperatures along the length of the discharge channel in a short duration, kinetic theory dictates gaseous molecules undergo a rapid increase in pressure and thus expand outward from the lightning creating a shock wave audible as thunder. Since the sound waves propagate not from a single point source but along the length of the lightning's path, the sound origin's varying distances from the observer can generate a rolling or rumbling effect. Perception of the sonic characteristics is further complicated by factors such as the irregular and possibly branching geometry of the lightning channel, by acoustic echoing from terrain, and by the typically multiple-stroke characteristic of the lightning strike.


    A portion of your original comments,
    and note you have shown NO LINKS to back up your claims....


    I don't believe for a second that is the main cause for the thunder. It may contribute a little as some water molecules are ionised. But that accounts for only a tiny proportion of lightning strikes.

    Being an avid storm chaser and photographer for many years. I can categorically state that I have seen 100's, probably 1000's of lightning strikes where there was no rain. There is ALWAYS thunder !



    Dave
     
    Last edited: Sep 23, 2018
  12. Sep 23, 2018 #11

    boneh3ad

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    The scientific rigor in this thread is staggering.
     
  13. Sep 24, 2018 #12
    Listen to a hot summer day no rain lightning strike it makes a crackling sound there is no BOOM thunder sound that echos across the country side for 10 seconds like a dynamite explosion. When I lived in Arizona we use to get heat lightning July & Aug 114 degrees with 4% humidity that came from no where in the sky with no clouds if you look very close you see a long skinny lightning spark & a tiny crackling spark sound. Several people on the electronic form made videos of discharging a large capacitor bank into a spoon of water instant steam produces an extremely power explosion = to dynamite. 1 lb stick of dynamite contains 3.2 oz of nitro = to about 3.5 tablespoons of water vaporized in less than 1/1000 of a second with 300 meg watts of power from a capacitor bank. A very powerful 1/2 mile long lightning strike will travel through many times more water than 3.5 tablespoons.
     
    Last edited: Sep 24, 2018
  14. Sep 24, 2018 #13

    russ_watters

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    Did you actually bother to calculate the density of liquid water in a rainstorm and the effect of heating it vs heating the air? It should be easy to take a hypothetical 1 square foot by 10,000 foot column of air and rain, calculate how much air and rain are in it and calculate how much each expands if their temperature is raised by a certain amount. I think you will find that the actual density of water is quite small, so the expansion of the air is a bigger factor.

    Edit: I'm impatient. By my calculation, 10,000 cubic feet of a medium hard rainstorm contains about 3 ounces of liquid water and 750 lb of air.
     
  15. Sep 24, 2018 #14
    We beat that, although it was a plasma arc rather than puny sparks from a van de Graaf generator. :-)

    https://phys.org/news/2011-11-extra-long-electrical-arcs-energy.html

    Cheers
     
  16. Sep 24, 2018 #15

    davenn

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    You are not understanding the process .... Did you even read what I quoted a few posts ago ?

    The sound the thunder makes is based on a number of variables .....
    1) distance to the strike .... very close ones are the very common intense crack sounds with almost no longer period ( drawn out) rumbling
    2) whether the strike was a single discharge or multiple ones down the same path
    3) whether it was a multi path across the sky discharge ... produces multiple sets of sound shock waves that radiate out
    4) the terrain and or clouds also have a distinct effect on lengthening out the rumbling ... aka echoes
    as the sound bounces between cloud and ground and back up again, as well as between the cloud masses

    There are probably other causal effects but above would be the main ones
    and all those effects interact


    Dave
     
  17. Sep 25, 2018 #16

    256bits

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    Cuz you hear all of the sound at the same time ( no time lag ), with very little reflections, so it is a snap.


    Also, some more notes on effects of lightning, oxygen molecule splitting and ozone production., as well as NOx production.
    https://www.compoundchem.com/2018/07/31/thunderstorms/

    so, even that tiny little spark, as well as sparks from electric motor cummutator produce ozone.
    In essence that little spark is a very similar to the lightning associated with a train storm, though on a much smaller scale.
     
  18. Sep 25, 2018 #17

    russ_watters

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    It's also a short spark (in distance more than time), so the sound has a short duration. For lightning that isnt parallel to you, the slow speed of sound stretches the duration of the thunder.
     
  19. Sep 25, 2018 #18

    ZapperZ

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    @gary350 : you were asked, way in the beginning, for a link or a source to back up your first post. You have not done this, and I'm surprised the Mentors are letting you get away with it.

    I want to know what is this ".... newest research information ... "

    Zz.
     
  20. Sep 25, 2018 #19
    @256bits I thought the noise like you describe is from the breakdown strength of the air at/around a conductor. Not the physical humming of a transformer, but like touching 2 leads together and 'hearing' the spark. Oddly, water increases the conductivity of the air and so increases the intensity of the discharge you hear. We were always taught in electronics school that the clap from lightning was from the created vacuum (or close enough) from the lightning collapsing under atmospheric pressure after the bolt.
     
  21. Sep 26, 2018 #20

    Tom.G

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    I would hazard that part of the thunder is from the conductive channel collapsing after the discharge. Although not lightning, I was once in a store when an oil tanker blew up in the harbor about six miles away. The noise from the explosion was accompanied by the door swinging open outward.
     
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