lehpron
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How Does Lightning Make Thunder?

Thu Sep 12, 2002 4:56 am

Okay, the way I see it is that lightning is light, or electricity in motion  Smile- ), or energy. It is massless. Thunder can be thought of as the shock wave of the lightning breaking the speed of sound. How does something massless pass the speed of sound and break out a huge shockwave called thunder?

As Johnny Cochran would say, "That doesn't make sence."
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 5:05 am

Sure it does lephron. What happens is that the electricity, while massless, is not heatless. Instantly heating up to tempuratures hotter than the sun's corona, the air inside & immediately outside the lightning bolt is displaced. When the heat dissapears, the sir comes crashing back into that void at far greater than the speed of sound and WHAM!!! Thunder.
 
redngold
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 5:07 am

The shockwave from lightning produces thunder. The lightning itself sounds like a very loud static spark (essentially what it is anyway) and if you are near a cloud-ground strike you will hear a very loud "CRACK!"

The thunder you hear is the result of superheated air expanding suddenly, producing an explosive noise.

Thunder noise is also affected by the path of the lightning and the environment in which it occurs. If you hear thunder that sounds like "crackle, crackle, crackle, BOOM!" then the lightning probably had several branches before the main channel was established. If you hear rolling thunder, you're most likely in a valley or up against a mountain which created echoes; or you are far away.

Check out this page for some clips of different thunder and more detailed explanations:
http://www.wvlightning.com/thunderc.html

Cheers,
redngold
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777236ER
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 5:18 am

Soooo many different ways to look at it. Remember Einstein? Energy and mass are interchangable. Consider the energy of a lightening strike. The electric field strength required for a discharge is around about 5x10^5 V/m.

So the moving electrons have lots of charge. LOTS of charge. They've got oodles of energy. But energy is interchangable with mass. These electrons are moving close to the speed of light, so we can apply the principle. Considering the energy of the electrons as mass, each electron has to have kinetic energy. Where does the kinetic energy go? Well, light, heat AND sound. Simplistic description, but I don't know how advanced you want it. If you want I can go through all the maths, and if I'm really in a happy mood I can prove lots of this by first principles.
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jwenting
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 6:02 am

you're all almost right  Smile/happy/getting dizzy

A lightning bolt creates a superheated plasma. When this cools it creates a partial vacuum. The thunder is the sudden collapse of this vacuum by air intruding upon it.
So not an effect of explosion, but rather implosion.

The electrical energy from the lightning is not discharged into sound. It is used in part (large part) to create the plasma through which it is conducted into the earth where it grounds.

As to sound, sound can only exist when there is something to move. Without matter, sound cannot exist. Electricity too is dependent on matter, as it is transmitted by the transfer of charge between drifting electrons (never mind the drawings in highschool physics books where they depict electricity as moving electrons, if that were the true principle you'd have to wait an hour or more for a lamp to start burning when you plug it in, electron drift is measured in centimeters per minute at most).
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777236ER
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 6:17 am

The electrical energy from the lightning is not discharged into sound. It is used in part (large part) to create the plasma through which it is conducted into the earth where it grounds.


Never the less, electrical energy is transfered into sound energy. Whether or not the cooling (and the loss) of the plasma causes the sound waves is thorny.

The electrons ARE accereated by the electrical field. They're given oodles of kinetic energy. As a consequence of the electron motion, plasma is formed. Once its formed it helps with the conduction, but its formed BECAUSE of election motion in the form of "streamers". As electrons have very high energies and ionise neutral air molecules by collision. The high energies are caused by the electric field, which accelerates the electrons. Mass and energy are interchangable, remember? The electrons have insignificant mass, but with the energies they have they provide what is seemingly a larger mass. The sound waves are caused by the collision and ionisation of the electrons with the oxygen/nitrogen atoms, but also by the CREATION of plasma as well as the loss of plasma once the point discharge current is over.

as it is transmitted by the transfer of charge between drifting electrons

Errrrr.....is this some new fundamental particle we're missing here? Electrons can move very fast. In fact, the CRT in your TV uses electrons moving near the speed of light. Mass and energy are interchangable only at speeds near the speed of light, and as electrons in this instance are moving near the speed of light its valid in this instance.
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BO__einG
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 7:43 am

Lightning is an excellent example of an Exothermic Reaction. Heat/Light/Sound is all part of the properties of an Exothermic Reaction.

Usually this is used to define Chemical Changes that occur such as TNT as that obviously gives off heat/sound/sometimes light/ and a shitload of energy.


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lehpron
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 8:13 am

"It is used in part (large part) to create the plasma through which it is conducted into the earth where it grounds."

If water is a conductor, like rain, why doesn't the bolt make straight paths into ground? What affect does the Earth's magnetic field has on moving charges in bolts or vice versa?

Plasma is what creates O3, right? The stuff that is depleting & non-abundant in our ozone, or it IS the ozone; in our atmosphere?




Gotta side question: if I attached a LONG copper wire to the ground and the other end to a model rocket and launched it into a storm cloud, would I be extending the ground and there by increasing the chances of a deliberate strike?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
tbar220
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RE: How Does Lightning Make Thunder?

Thu Sep 12, 2002 8:20 am

Probably not a deliberate strike, but rather increasing the chances of having your rocket struck by lightning  Laugh out loud
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