# which occurs first lightning or thunder?

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which is which?

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Thunder is the result of lightning. Lightning happens (or at least starts) first.

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Sound travels approximately 340 m/s in air.

So if you see lightning and start counting seconds,

divide them by 3,

and you have distance to lightning in kilometers.

Suppose so you counted seconds to 5

d = v*t

d = 340 m/s * 5s = 1700 meters

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Lightening is a spark, like when you touch a door knob after walking across a carpet, and you get shocked. The sound and spark occur at the same time. However, sound travels slower than light, so at a distance you see the lightening and later hear the thunder.

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which is which?

Thunder occurs a few fractions of a second after lightning but arrives a few seconds later due to the difference in speed propagation between light and sound. See: https://en.wikipedia.org/wiki/Thunder#Calculating_distance

Edited by zztop

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Lightening is a spark, like when you touch a door knob after walking across a carpet, and you get shocked. The sound and spark occur at the same time. However, sound travels slower than light, so at a distance you see the lightening and later hear the thunder.

But the spark causes the sound. It has to happen first.

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Is thunder like a sonic boom?

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But the spark causes the sound. It has to happen first.

Perhaps, but in a vacuum there is neither spark nor sound, merely subatomic particles moving. The spark is ionized molecules, which must be moved by a charge. The sound is movement of molecules. I don't know if anyone has investigated what happens in the first nanoseconds of a spark. It is an interesting question.

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Lightning and thunder don't occur in a vacuum.

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Is thunder like a sonic boom?

Yes.

Thunder is the sound caused by lightning. Depending on the distance and nature of the lightning, thunder can range from a sharp, loud crack to a long, low rumble (brontide). The sudden increase in pressure and temperature from lightning produces rapid expansion of the air surrounding and within a bolt of lightning. In turn, this expansion of air creates a sonic shock wave, similar to a sonic boom, which produces the sound of thunder, often referred to as a clap, crack, peal of thunder, or boom. ...

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Lightning heats air.

Heated air expands.

Expansion of air produces a sonic wavefront.

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Perhaps, but in a vacuum there is neither spark nor sound, merely subatomic particles moving. The spark is ionized molecules, which must be moved by a charge. The sound is movement of molecules. I don't know if anyone has investigated what happens in the first nanoseconds of a spark. It is an interesting question.

Photons move in a vacuum. They are produced by the excited electrons of the ionised molecules as they drop back down to their resting level..

Edited by StringJunky

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Photons move in a vacuum. They are produced by the excited electrons of the ionised molecules as they drop back down to their resting level..

True, I didn't fully expound during my previous statement.

A potential difference in a vacuum moves electrons between two conductors (anode and cathode), but no spark is produced. I don't think other subatomic particles would move between them, nor photons. But, there is no such thing as a perfect vacuum, so some atoms will exist and can become ionized. They would emit photons. Electrons hitting the anode would cause heat, and at some point atoms from the anode would be released into the vacuum, probably as ions. Eventually enough anode material would be in the vacuum to cause a spark. Often cathodes are heated to allow electrons to flow more freely. Atoms might escape from the cathode, too.

This isn't on-topic, but is a more complete explanation of a potential difference in a vacuum. I'm not sure it's all correct.

Edited by EdEarl

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True, and maybe dark matter particles.

I was responding to this:

Perhaps, but in a vacuum there is neither spark nor sound, merely subatomic particles moving.

Edited by StringJunky

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Perhaps, but in a vacuum there is neither spark nor sound, merely subatomic particles moving. The spark is ionized molecules, which must be moved by a charge. The sound is movement of molecules. I don't know if anyone has investigated what happens in the first nanoseconds of a spark. It is an interesting question.

Was the negative vote here a mistake?

This could certainly have been better phrased, but deserving of a negative vote?

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Was the negative vote here a mistake?

This could certainly have been better phrased, but deserving of a negative vote?

I never saw the neg but if there was it was unwarranted. There is a possibility as I passed my cursor to move to another part of the page it hit a red; that's happened before. I use a touchpad which can inexplicably do things I don't want it to do.

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I edited the mention of dark matter particles out of my post, and expounded on, "Perhaps, but in a vacuum there is neither spark nor sound, merely subatomic particles moving," and probably said too much with additional omissions of other relevant info.

Edited by EdEarl

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Lightning occurs first. It's an electric spark across a very high potential difference.

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They happen at the same time. But since light travels faster than sound, you see the lightning before you hear the thunder.

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They happen at the same time. But since light travels faster than sound, you see the lightning before you hear the thunder.

What causes the thunder, then?

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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.

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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?

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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.

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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.

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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.