# Thunderstorms and mistaken parents



## HareBrain (Apr 29, 2017)

When I was growing up, my parents told me that to work out how far away a thunderstorm was, you counted the seconds between the lightning flash and the noise, and it was one mile for every two seconds. A friend I spoke to a while back said the same thing, and one I talked with today said his parents had told him a second per mile.

If we take the speed of sound to be 600 mph (for ease of calculation) that's actually six seconds per mile. That would make a storm with a gap of twelve seconds still only two miles away, and I'm pretty sure I've never counted one longer than that. But you'd have thought a bang like that would be audible several miles away.

Was anyone else fed the same misinformation by their parents? How might their collective misunderstanding have arisen? (Or was it deliberate, to make the storms seem farther away than they really were and thus not so threatening?) Or is there anything wrong with my reasoning? Would thunder really not be audible over a distance of more than a couple of miles?


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## The Judge (Apr 29, 2017)

Yep, I grew up with the 1 second = 1 mile rule, though I couldn't say who told me that, so I'm casting no blame on my parents for this.

Heavy-gun fire can be heard over prodigious distances if conditions are right, so I'd also expect thunder to be heard over more than a couple of miles, but perhaps the very fact there's a storm means that conditions aren't right for sound carrying?  Low clouds and heavy rain might act as noise mufflers perhaps?  Though I thought I'd read somewhere that clouds can act as boards that sound can bounce off so that noise can be heard even further away. 

I await some scientific brains to straighten things out!


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## TheDustyZebra (Apr 29, 2017)

Yup, my rule of thumb has always been 1 second = 1 mile, and I hadn't really thought about it.

As a parent, I can tell you without a doubt that parents lie. But I think if that one were deliberate, to ease childish fears, it certainly started many generations back, and it's been passed down because grandma cut the ends off the ham.


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## HoopyFrood (Apr 29, 2017)

Yes, one second = one mile.


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## Ursa major (Apr 29, 2017)

TheDustyZebra said:


> it's been passed down because grandma cut the ends off the ham


That's something I've never heard before. (I had to look it up on the Interwebs.)


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## TheDustyZebra (Apr 30, 2017)

Ursa major said:


> That's something I've never heard before. (I had to look it up on the Interwebs.)



And you found it? I'm curious what the interwebs had to say about that. They can't tell the joke as well as my mother did.


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## Danny McG (Apr 30, 2017)

I'd never heard it either

Critical-Thinkers.com - Critical thinking, strategic thinking, creative thinking blog

Similar to the defrosting the chicken story..
Mother and Gran visit the young newlywed house. She has a chicken defrosting on the kitchen worktop with a colander upside down over it.
Granny queries this and the young bride tells her that's how she was shown to do it by her mother, Granny asks mother who explains that's how she too was shown to do it. Granny says "Yes dear, but neither of you two have a cat"


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## TheDustyZebra (Apr 30, 2017)

Ha, yes.

For those who don't want to look it up, and bearing in mind that I don't tell it as well as my mother did...

Young new bride is making a ham for dinner, and she cuts the ends off it and puts it in the pan. Husband asks why she did that, and she says, "My mother always cuts the ends off the ham before she puts it in the pan." Some time later, they're at mom's house, and they ask her why she does that. Mom says, "My mother always cut the ends off the ham before she put it in the pan." Forward to a future dinner with Grandma, and they inquire of her. She says, "I didn't have a big enough pan."


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## hopewrites (Apr 30, 2017)

I think the counting discrepancy can also be accounted for with the idea that when we're stressed (such as durring a scary storm) we would count faster. I know I never had a stop watch to time flash to sound ratios.


My dad never stipulated a mile, just that if you count, that's how far a way it is. Miles feet yards years could have been anything.


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## Lumens (Apr 30, 2017)

I heard this as a kid in Norway, but it was in kilometers, not miles. Not from parents but an other kid. I never liked him much, so it is with some smug satisfaction that I can dismiss him now, even though I haven't seen him for decades.


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## Brian G Turner (Apr 30, 2017)

Never realised this. 

Just checked on another website, which suggests dividing the seconds by 5 to get a rough idea of miles.


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## HareBrain (Apr 30, 2017)

Glad to hear it wasn't just me. I only questioned it a few years ago for my writing: a ship's magazine goes up, and I needed to be sure how long it would be before the sound reached the observers two miles or so away. The answer -- 10-12 seconds -- seemed so ludicrous I downplayed it to "seconds later". And I think it seemed so unreal not just because witnessing a distant explosion isn't within most people's experience, but because of TV and film, where distant noises are almost always heard without delay.



The Judge said:


> Heavy-gun fire can be heard over prodigious distances if conditions are right



The explosion of the Lochnagar mine at the Somme was heard from London, maybe 80 miles away. It would have taken that sound over _six minutes_ to get there. Which seems bizarre, to me, even though it's not the least strange that a jet travelling at Mach 1 would take that long.


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## Ursa major (Apr 30, 2017)

Note that shock waves travel faster than the speed of sound.


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## Danny McG (Apr 30, 2017)

Back in 1982 'The Poltergeist' was released and, just before the evil spirits snatch the little girl, there is a thunderstorm approaching.
Dad calms his two kids by explaining the lightning flash/ thunderclap 'distance rule' to them.
I always assumed that was correct until this thread. Curse you Hollywood!


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## Venusian Broon (Apr 30, 2017)

Never heard the idea that a second counted between flash and thunder meant a 1 mile/kilometre distance.

My dad being a physicist didn't make any comment on distance because of time delay (He probably would have launched into a lecture on atmospheric conditions that can change the speed of sound ). However, I remember him telling me to count the seconds between flash and thunder, then compare consecutive events to gauge if the storm was coming towards or away from us, like @hopewrites. Which is nice and easy & there are no worries about actual distance.

As for other misinformation when I was a very young one, he told me how a laser worked, which I think was grossly oversimplified. Which might count.


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## HareBrain (Apr 30, 2017)

Venusian Broon said:


> He probably would have launched into a lecture on atmospheric conditions that can change the speed of sound



With what effect, do you know? Obviously sound travels much faster through water, but does that work on a pro-rata basis for degrees of rainfall/humidity?


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## Overread (Apr 30, 2017)

There are loads of cases like this.
Humans are inherently very trusting of information and as a result the first information we hear about something we take as fact and it actually takes a lot of counter information to dissuade most people. Esp when the information is proven correct over a long period of time - even if correct is very rough (storms that have longer seconds between the flash and the bang ARE further away). 

We actually have to be trained to critically think and to question both new information and old information we learned. This is why newspapers like the Daily Mail work - because most people won't question nor dispute - especially on topics that they otherwise are not involved in.


Another fun one is blue blood. 
Our blood is never actually blue Blue veins/red blood (Page 1) - General Biology - Ask a Biologist Q&A

However because it looks blue on our veins at a casual glance; because we know that oxygen does make blood a richer red colour; because the diagrams in nearly every single biology book have red for oxygenated and blue for de-oxygenated - we all (including many teachers!) get the misunderstanding. 

It often takes a very long time for "Facts" like this to be disproved because they persist very readily within society and many are established when we are young and thus form the foundations of our understanding of latter things. It's far harder to change the foundation.


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## The Ace (Apr 30, 2017)

Mum said it was God chucking his wardrobe downstairs (she wouldn't elaborate).


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## Venusian Broon (Apr 30, 2017)

HareBrain said:


> With what effect, do you know? Obviously sound travels much faster through water, but does that work on a pro-rata basis for degrees of rainfall/humidity?



My very quick understanding is that the speed of sound varies most with temperature. That's because a higher temperature gas means that the individual gas molecules will have an higher average kinetic velocity - hence the sound wave can take advantage of this extra velocity and propagate faster.

Here's an approximate equation I found:

*Speed of sound c ≈ 331.3 + (0.6 × ϑ) in m/s *_where *ϑ*_ = temperature in deg C.

The actual equation for an ideal gas is c=√ (γR*T*), so it's actually proportional to the square root of temperature, but let's not complicate it ....

Because of this variance then the speed of sound will vary indirectly with altitude (because of adiabatic cooling. Or put simply it's colder on mountains than at sea level. There's an easy equation for that if you want it also!)

It also varies with humidity (humidity comes in the 'y' part of the ideal gas equation, which is the ratio of specific heats of the air you have...)

However thankfully you can also approximate it

*Speed of sound c ≈ 331.3 + (0.6 × ϑ)  + (0.0124 × Rel. Humidity) in m/s *_where *ϑ*_ = temperature in deg C and *Rel. Humidity* is 0-100% (or maybe beyond if you supersaturate, 'cause you can.)

The figure most usually given for the speed of sound are for conditions at sea level, with dry air at 20 dec C, or 343 m/s.

However as you can see the change because of temperature is really not that much of a difference. Hence 3 seconds for a Km when calculating lightning distances with all earth-like conditions is broadly correct


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## Danny McG (Apr 30, 2017)

Seems straightforward enough when you put it like that .

(slow blink of bafflement)


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## Lumens (Apr 30, 2017)

100% humidity means you're under water, right?


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## Biskit (Apr 30, 2017)

The Judge said:


> Heavy-gun fire can be heard over prodigious distances if conditions are right, so I'd also expect thunder to be heard over more than a couple of miles, but perhaps the very fact there's a storm means that conditions aren't right for sound carrying? Low clouds and heavy rain might act as noise mufflers perhaps? Though I thought I'd read somewhere that clouds can act as boards that sound can bounce off so that noise can be heard even further away.



The suspended or falling water droplets (or even ice crystals in clouds) will both absorb and reflect the sound.  I would certainly expect to get muffling effects through rain that would limit the range of the sound from the lightning.  You might also find local rain noise masking the sound from more distant lightning.


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## Kylara (Apr 30, 2017)

My quick googling and using engineer brain in my partner has revealed that the it takes 4.7 seconds for sound to travel a mile. 

That is all. I have no further input for pressure or temperature or anything else and in fact I thought this was about people mistaking parents during thunderstorms...


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## The Judge (May 1, 2017)

The cutting ends off ham and defrosting chickens reminds me of the story _Chromium_, in Primo Levi's _The Periodic Table_, where he relates exactly the same blind following of a formula in various paint/varnish factories during and after WWII.  In one anecdote he tells how a prescription book called for two slices of onion to be introduced into linseed oil as it was boiling, which he thought odd to say the least.  It turned out that before thermometers had come into use the temperature of the oil had to be assessed by other means, one of which was to immerse a slice of onion into the oil and if it fried, the boiling was finished.  "Evidently, with the passing of the years, what had been a crude measuring operation had lost its significance and was transformed into a mysterious and magical practice."!


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## Biskit (May 1, 2017)

I had something similar from an early boss who was talking about a successful grease formulation that was going from small, hand-crafted batches to bulk production.  They re-created it in the larger scale but it never came out right.  Finally, they got the old guy who did the hand mixing to take them through the whole process.  At some point the guy spat in the mix for luck - the little bit of moisture was the necessary extra ingredient.


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