Jump to content


Photo
- - - - -

which occurs first lightning or thunder?


  • Please log in to reply
44 replies to this topic

#21 AshBox

AshBox

    Quark

  • Senior Members
  • 43 posts

Posted 11 January 2017 - 10:20 AM

 

 

What causes the thunder, then?

Hi, swansont

According to me, When lightning travels from clouds to the ground, it opens a little hole, or channel, in the air. Once the lightening disappears, the hole collapses and reverts back inwards. The resulting sound is thunder. Light travels at a rate of 186,282 miles per second, allowing the human eye to see a flash of lightning immediately as it happens. Sounds travels at the much slower rate of 1,087 feet, or one-fifth of a mile per second.

 

The rate at which the sound waves travel varies, depending on the temperature of the air and the wind's speed. Thunder appears to rumble or roll at times due to zigzag lines, or forks, that occur when lightning that strikes is not visible. These forks can branch out over several miles. These branches of lightning are further from the ground; therefore, they produce sounds of thunder, which take longer to be heard than the large bolt of lightning that originally produced the branched-out forks.


  • 0

#22 DrKrettin

DrKrettin

    Atom

  • Senior Members
  • 363 posts

Posted 11 January 2017 - 10:35 AM

They happen at the same time. 

 

You explain in a later post, as everybody had already said, that lightning causes thunder. If A causes B, can A and B ever be simultaneous?


  • 0

κατθάνοισα δὲ κείσῃ οὐδέ ποτα / μναμοσύνα σέθεν /  ἔσσετ' οὐδὲ †ποκ'†ὔστερον· οὐ / γὰρ πεδέχῃς βρόδων / τῶν ἐκ Πιερίας· 


#23 swansont

swansont

    Evil Liar (or so I'm told)

  • Moderators
  • 35,487 posts
  • LocationWashington DC region

Posted 11 January 2017 - 10:43 AM

 

You explain in a later post, as everybody had already said, that lightning causes thunder. If A causes B, can A and B ever be simultaneous?

 

 

Yes, exactly the point I had in mind.


  • 0

Minutus cantorum, minutus balorum, minutus carborata descendum pantorum          To go to the fortress of ultimate darkness, click the up arrow ^

I am not a minimum-wage government shill.             Forget it, Jake — it's Crackpottown.

My SFN blog: Swans on Tea                                                           

 

 

                                                                                                                     

 

 


#24 EdEarl

EdEarl

    Primate

  • Senior Members
  • 2,926 posts
  • LocationTexas, USA

Posted 11 January 2017 - 12:45 PM

Wikipedia
 
Return stroke

High-speed photography showing different parts of a lightning flash during the discharge process as seen in Toulouse, France.
Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, a massive electrical discharge follows. This is the 'return stroke' and it is the most luminous and noticeable part of the lightning discharge.
A large electric current flows along the plasma channel from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of the ground. Called step potentials, they are responsible for more injuries and deaths than the strike itself.[citation needed] Electricity takes every path available to it.[28] A portion of the return stroke current will often preferentially flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes.

The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a positive ground to cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 1×108 m/s.[29]

The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 50,000 K, causing it to brilliantly radiate with a blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder.


  • 0

Be kind whenever possible. It is always possible. -- Tenzin Gyatso, the 14th Dalai Lama.

Anyone who isn't confused really doesn't understand the situation. -- Edward R. Murrow

Uncertainty Principle = Shit Happens.

 


#25 StringJunky

StringJunky

    Genius

  • Senior Members
  • 5,720 posts
  • LocationUK

Posted 11 January 2017 - 01:30 PM

 

Wikipedia
 
Return stroke

High-speed photography showing different parts of a lightning flash during the discharge process as seen in Toulouse, France.
Once a conductive channel bridges the air gap between the negative charge excess in the cloud and the positive surface charge excess below, a massive electrical discharge follows. This is the 'return stroke' and it is the most luminous and noticeable part of the lightning discharge.
A large electric current flows along the plasma channel from the cloud to the ground, neutralising the positive ground charge as electrons flow away from the strike point to the surrounding area. This huge surge of current creates large radial voltage differences along the surface of the ground. Called step potentials, they are responsible for more injuries and deaths than the strike itself.[citation needed] Electricity takes every path available to it.[28] A portion of the return stroke current will often preferentially flow through one leg and out another, electrocuting an unlucky human or animal standing near the point where the lightning strikes.

The electric current of the return stroke averages 30 kiloamperes for a typical negative CG flash, often referred to as "negative CG" lightning. In some cases, a positive ground to cloud (GC) lightning flash may originate from a positively charged region on the ground below a storm. These discharges normally originate from the tops of very tall structures, such as communications antennas. The rate at which the return stroke current travels has been found to be around 1×108 m/s.[29]

The massive flow of electric current occurring during the return stroke combined with the rate at which it occurs (measured in microseconds) rapidly superheats the completed leader channel, forming a highly electrically conductive plasma channel. The core temperature of the plasma during the return stroke may exceed 50,000 K, causing it to brilliantly radiate with a blue-white color. Once the electric current stops flowing, the channel cools and dissipates over tens or hundreds of milliseconds, often disappearing as fragmented patches of glowing gas. The nearly instantaneous heating during the return stroke causes the air to expand explosively, producing a powerful shock wave which is heard as thunder.

 

Nearly instantaneous is still slower than simultaneous.


  • 1

 Education, like life, is a journey not a destination


#26 EdEarl

EdEarl

    Primate

  • Senior Members
  • 2,926 posts
  • LocationTexas, USA

Posted 11 January 2017 - 02:13 PM

Nearly instantaneous is still slower than simultaneous.

True, but having been close to a lightning strike, I can say there is no perceivable difference between flash and sound, and that up close thunder sounds like a loud spark, "crack."


  • 0

Be kind whenever possible. It is always possible. -- Tenzin Gyatso, the 14th Dalai Lama.

Anyone who isn't confused really doesn't understand the situation. -- Edward R. Murrow

Uncertainty Principle = Shit Happens.

 


#27 Bender

Bender

    Atom

  • Senior Members
  • 289 posts

Posted 11 January 2017 - 02:15 PM

Moreover, it is the heating which happens nearly instantaneous. The movement of air can only happen after the heating.
  • 1

#28 DrP

DrP

    Molecule

  • Senior Members
  • 1,660 posts
  • LocationUK

Posted 11 January 2017 - 02:42 PM

QUOTE EE: ..."no perceivable difference.."

 

Of course not, how would your human senses detect that? The spark, however, DOES come before the bang....  there is no 'perhaps' about it, we know this.

 

 

PS: The use of "perhaps" and confusing the simple issue by talking about irrelevant ions in a vacuum was why I gave you a -1 earlier, although studiot thought your post worth a +1. My - 1 may have been a bit harsh and I do now regret it, but I have given you loads of +'s in the past (I think) so only thought it right to give you a neg too when you throw doubt on what we know to be true but saying "perhaps".   I hate saying when I have given positive or negative rep - there is as reason it is confidential, and I hate this recent sycophantic trend of creepily posting "I gave you +1 for that"...  it is so slimy and bloody irritating.


  • 2

"Tonight I am going to party like it's on sale for $19.99"! - Apu Nahasapeemapetilon


#29 EdEarl

EdEarl

    Primate

  • Senior Members
  • 2,926 posts
  • LocationTexas, USA

Posted 11 January 2017 - 03:01 PM

Perhaps you can clear up something I do not understand. Electrons don't move at the speed of light, but IDK how fast ions are created nor how fast an atom heats as it becomes ionized. A spark flows through ions; thus, I assume a spark is the movement of electrons as quickly as atoms become ionized. How much delay is there between ionization and the air becoming superheated to create the crack of a spark?


  • 0

Be kind whenever possible. It is always possible. -- Tenzin Gyatso, the 14th Dalai Lama.

Anyone who isn't confused really doesn't understand the situation. -- Edward R. Murrow

Uncertainty Principle = Shit Happens.

 


#30 DrP

DrP

    Molecule

  • Senior Members
  • 1,660 posts
  • LocationUK

Posted 11 January 2017 - 03:16 PM

I do not know what the delay is Ed, but there has to be some delay because one causes the other. You could ask when exactly does the spark begin?... Is it a spark when it is first visible or is it a spark when the first photon of light is emitted?  The time measurement from these points will be different (micro seconds?). I do not even know if the exact point the discharge actually becomes defined as a spark. For the spark to cause thunder though it would need to be huge (although small sparks do make a little crack sound). None the less, this energy released to the spark heats the air and causes it to expand causing the thunder...  which happens (micro seconds?) AFTER the discharge. How could it be different?


My assumption would be that you can see the light before the air has started to expand - thus the sound comes after the light. (when I say 'see' here I mean the exact point the light leaves the spark, not when it enters your eye.)


Edited by DrP, 11 January 2017 - 03:16 PM.

  • 0

"Tonight I am going to party like it's on sale for $19.99"! - Apu Nahasapeemapetilon


#31 EdEarl

EdEarl

    Primate

  • Senior Members
  • 2,926 posts
  • LocationTexas, USA

Posted 11 January 2017 - 03:44 PM

Electrons jumping orbitals are instantaneous. When an electron makes an ion, is that movement instantaneous? Since that process pumps energy into an atom, there would be no light created. What causes the light? The blue color of ionized air seems to suggest that some electrons are moved to higher orbitals and fall back later; thus, generating light. If that is the source of light, then the electric current that ionizes and heats is invisible, and some time later light is created. However, IDK everything happening; thus, my assumptions may be wrong.

 

The superheated air/ions would create a pressure wave that spreads at the speed of sound, are you sure the pressure occurs after the light is created by electrons falling to a lower orbital, or is there more going on that I'm unaware of?


  • 0

Be kind whenever possible. It is always possible. -- Tenzin Gyatso, the 14th Dalai Lama.

Anyone who isn't confused really doesn't understand the situation. -- Edward R. Murrow

Uncertainty Principle = Shit Happens.

 


#32 DrP

DrP

    Molecule

  • Senior Members
  • 1,660 posts
  • LocationUK

Posted 11 January 2017 - 03:55 PM

I'll have to look that up when I am not at work, although I suspect you are over thinking it. When the terms lightening and thunder where introduced I do not know if they were defined tightly enough to determine the exact point in the discharge you deem the spark to be called lightening. The ionisation and energy releases you are talking about HAVE to happen before the sound though, surely, as it is this energy released by that that causes the superheating and the expansion and thus the sound. Anyway - unless I unearth something amazing and new when I look that up later I guess I can add no more. I will let a pure physicist answer you question. Regards.


  • 1

"Tonight I am going to party like it's on sale for $19.99"! - Apu Nahasapeemapetilon


#33 Bender

Bender

    Atom

  • Senior Members
  • 289 posts

Posted 11 January 2017 - 06:41 PM

The air in lightning gets considerably hotter than the sun. I assume that to be the primary source of the light. In other words: as soon as the air is heated, you have lightning.

 

Then again, it depends on defining when lightning and thunder start. Heating the air initiates both the emission of photons and the emission of a pressure wave, aka thunder. So while the time constant of the light being emitted is much smaller than for the sound wave, they are both initiated by the same event.


  • 0

#34 Ophiolite

Ophiolite

    Moderately Super

  • Resident Experts
  • 5,436 posts
  • LocationWithin sight of three battles

Posted 11 January 2017 - 06:52 PM

I hate saying when I have given positive or negative rep - there is as reason it is confidential, and I hate this recent sycophantic trend of creepily posting "I gave you +1 for that"...  it is so slimy and bloody irritating.

Going briefly off-topic, I believe that once or twice I have advised a poster that I've given them a +1. That, and an accompanying explanation, have been to emphasise (and perhaps expand on) how relevant, accurate, useful, agreeable, etc. their post was. (I'll leave you to wonder if the +1 on your post #32 was from me. :))


  • 0

I waited and waited for a response to my post and when none came I knew it must be from you.

Ashleigh Brilliant

 

One can never eliminate the concept of irreducible complexity as long as it is supported by inexplicable stupidity.

Ophiolite

 

 


#35 StringJunky

StringJunky

    Genius

  • Senior Members
  • 5,720 posts
  • LocationUK

Posted 11 January 2017 - 06:59 PM

The air in lightning gets considerably hotter than the sun. I assume that to be the primary source of the light. In other words: as soon as the air is heated, you have lightning.

 

Then again, it depends on defining when lightning and thunder start. Heating the air initiates both the emission of photons and the emission of a pressure wave, aka thunder. So while the time constant of the light being emitted is much smaller than for the sound wave, they are both initiated by the same event.

 The ionic discharge which brings forth  light - which is heat - superheats  the air molecules which then create a shockwave. It's got to get to that temperature first, which takes time, no matter how short. That is the order of events.


Edited by StringJunky, 11 January 2017 - 07:00 PM.

  • 1

 Education, like life, is a journey not a destination


#36 Bender

Bender

    Atom

  • Senior Members
  • 289 posts

Posted 11 January 2017 - 07:05 PM

Is the air heated by light? I would have thought it was heated by resistive heating, in which case the heating happens first and then causes both light and sound.


  • 0

#37 StringJunky

StringJunky

    Genius

  • Senior Members
  • 5,720 posts
  • LocationUK

Posted 11 January 2017 - 07:16 PM

Is the air heated by light? I would have thought it was heated by resistive heating, in which case the heating happens first and then causes both light and sound.

The heat is photons being emitted as the electrons in the ionised molecules go back to the rest state.


  • 0

 Education, like life, is a journey not a destination


#38 Bender

Bender

    Atom

  • Senior Members
  • 289 posts

Posted 11 January 2017 - 07:35 PM

But what part of the lightning we see is the photons being emitted in that way, and what part is photons being emitted because the air is hot?


  • 0

#39 StringJunky

StringJunky

    Genius

  • Senior Members
  • 5,720 posts
  • LocationUK

Posted 11 January 2017 - 07:39 PM

But what part of the lightning we see is the photons being emitted in that way, and what part is photons being emitted because the air is hot?

I've no idea about the wavelengths of the photons involved/emitted in each part. Pass :)


Edited by StringJunky, 11 January 2017 - 07:41 PM.

  • 0

 Education, like life, is a journey not a destination


#40 swansont

swansont

    Evil Liar (or so I'm told)

  • Moderators
  • 35,487 posts
  • LocationWashington DC region

Posted 11 January 2017 - 11:36 PM

Electrons jumping orbitals are instantaneous.


They are?
  • 0

Minutus cantorum, minutus balorum, minutus carborata descendum pantorum          To go to the fortress of ultimate darkness, click the up arrow ^

I am not a minimum-wage government shill.             Forget it, Jake — it's Crackpottown.

My SFN blog: Swans on Tea                                                           

 

 

                                                                                                                     

 

 





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users