Why is there lightning before thunder?

[Tom Bender]

The lightning is a warning to drop the cat before the clap of thunder. This time I didn't need bandaids on my stomach, just a small one on my hand.

[Jim Becker]

The answer...is distance and the speed of sound. So yea...don't ignore the flash if you have a cat in your arms!

[Bill Dufour]

Sound is about 5 miles per second. Light is instant for practical purposes on earth. So if lighting hits then 5 seconds later you hear the thunder it was one mile away. Note distance is straight line not just horizontal. Here most thunder is at least one mile high. So five seconds plus some for the horizontal distance as well.
Bill D

[Steve Demuth]

Sound is about 5 miles per second. Light is instant for practical purposes on earth. So if lighting hits then 5 seconds later you hear the thunder it was one mile away. Note distance is straight line not just horizontal. Here most thunder is at least one mile high. So five seconds plus some for the horizontal distance as well.
Bill D

I think you mean 5 seconds per mile, Bill.

[Tom Stenzel]

I think you mean 5 seconds per mile, Bill.

At the sound of thunder my dog will run to the basement at about 5 miles a second.

Well, I haven't measured it but haven't dared get in the way.

-Tom

[Jim Becker]

I think you mean 5 seconds per mile, Bill.

Yup...about 1100 feet per second which is about 5 seconds to get to a mile.

[Alan Rutherford]

Yup...about 1100 feet per second which is about 5 seconds to get to a mile.

Or about 1125 fps, depending on tenperature, altittude, your references and perhaps attitude. If you really want to see that subject discussed to death find a rimfire-oriented gun forum and a debate about supersonic vs subsonic ammunition, how you define those and why and whether it matters. In my experience, a squirrel can get to the other side of the tree whether the ammo is supersonic or not.

That's true about the height of the thunderstorm, but now that we live on the fringe of the lightning capital of the country I've noticed that the sound comes from the whole length of the lightning bolt, including where it hits the ground, if it does. I saw a lightning strike on a neighbor's tree from inside my car about 100 yards away a few years ago and I assure you there was no delay waiting for the sound to travel down from the cloud. Part of me was wishing for instant replay but another part says once was enough.

[John Stankus]

Speed of light 2.998 x 108 m/s which translates to about 5.4 microseconds per mile (In my ultrafast spectroscopy days the rule of thumb was a foot for every nanosecond)
Speed of sound in dry air is about 343 m/s (varies with temperature and humidity) which translates to about 4.7 seconds a mile
Higher humidity would increase the speed of sound, since the water molecule is lighter than nitrogen or oxygen.


Reminds me of the question that always trips up my students in the physical chemistry lab...What is more dense, dry air or humid air?


Dry air is more dense, again this is due to water molecule being lighter than nitrogen, N2 or oxygen O2.

John

[Steve Demuth]

That's true about the height of the thunderstorm, but now that we live on the fringe of the lightning capital of the country I've noticed that the sound comes from the whole length of the lightning bolt, including where it hits the ground, if it does. I saw a lightning strike on a neighbor's tree from inside my car about 100 yards away a few years ago and I assure you there was no delay waiting for the sound to travel down from the cloud. Part of me was wishing for instant replay but another part says once was enough.

Having been in both barns and small planes struck by lightning, I can affirm that the instantaneous and unexpected combined flash and bang (to put it mildly) may require a moment or two to recover from. I recall as a young fella, working furiuosly to get a couple of loads of square bales into the neighbors' barn as a massive prairie storm (Greg Brown: "Clouds roll in from Nebraska; dark chords on a big guitar" says it best, musically) rolled in. I was up in the peak stacking when a bolt hit the (grounded to the lightning rod system) cupula just above me - I was maybe 15 ft away from the terminus of the strike. Holy shit. Not too different from the percussion you feel if you've ever been right next to a black powder cannon being fired - except then you typically know it's coming, so you're a little less likely to need a change of underwear after.

[Rob Damon]

It was a joke about a cat not a question of scientific inquiry............:D:D:D

[Bill Dufour]

I agree, I said it backwards. It is five seconds per mile.
Bill D

[Kev Williams]

Supposedly there's a story -or maybe a movie even as I don't remember the particulars, but how it goes is some guy was underwater when he heard an explosion... he then surfaced, and heard "another" explosion, so his story was there was 2 explosions-- but was eventually determined that it was just one explosion due to sound traveling nearly 4-1/2x faster in water than thru air, so he heard the same explosion twice...

[Alan Rutherford]

Lightning in real time: https://map.blitzortung.org/#1.26/-3.1/-110.8

Turning on the display of the number of strikes in each area right now shows over 7,000 recent strikes in the Gulf and the Tallahassee-Pensacola Florida area, quite a few in Alabama, a bunch in Oklahoma-Texas-Arkansas, and nowhere else in the world even close. Not much right here but we've been listening to the rumble.

[Malcolm McLeod]

I was in a limestone quarry (aggregate mine) once for 'a shot'. They back off 6ft from the active cliff face and drill a row of 12" holes 6ft OC spanning perhaps a 1/2 mile of the face, tie det cord to a rock and drop it to the bottom of each hole (~200'), then fill it with liquid explosive, 'splice' the det cords together, and clear the area. Objective is no rubble larger than a human head (all goes into crushers). Safety first :: there is even a lookout for low flying aircraft.

I was located on the mine floor, about 1/3 to 1/2 of a mile back from face - "FIRE".

Cliff face crumbles - dust rising - no sound. You can see a disturbance coming on the ground :: sand particles kicked up.

Buh-whuump! ...Seems like a sound (but it's not). Body feels a sharp thump.

Turned to Facility Electrician, "That wasn't as bad as" BOOM!! "I thought." Check eardrums for bleeding.

First shock arrived at the speed of sound in limestone. Second arrived at speed of sound in air.

No cats were harmed in the making of this aggregate. ...nor airplanes.

[Perry Hilbert Jr]

High school physics. We had a guy set off a large aerial mortar firework on one side of the river and had five people measure from the flash to the sound with stop watches. We threw out the two most extreme times and averaged the middle three. Then distance per second x time in seconds down to the hundredths. We came up within 30 feet of what the US Coast and Geodetic survey map had as the distance on a topographical map. Not far off for a group of high school kids and a 1.4 mile wide river. At the 4th of July a little town along the river has an impressive fireworks display for such a small town. We went down to the river to watch one night. The problem is that we were 7 miles south. The sound took over a half minute to get to us.

[Dave Zellers]

The lightning is a warning to drop the cat before the clap of thunder.
To paraphrase Rob Damon, look what you did. Rather impressive actually.

As a cat person, I can relate. :)

However , also loving all the science stories.

But this thread was about having a cat in your arms when lightening struck nearby. Ouch.

So to the science- I have experienced a direct hit (along with my wife and two single digit children) in the kitchen in a single story house so maybe ten feet above us. It hit the antenna and wiped out everything connected to it. EVERYTHING! My son lost his Nintendo and he was right in the middle of Zelda! Absolutely frightening for the moment that it happens. Climbing up on the roof the next day, there was no TV cable, only a white ash line on the shingles. Seriously impressive, and humbling.

And LOUD!

[michael langman]

When I moved in with my wife she would get in the hallway in the middle of the house during the spring,summer lightening storms we have every year.
I asked her why and she said that she was in her bed asleep during a lightening storm and her iron bed was catapulted across the room with her in it when she was 18.
The first year we moved into our house I was in the garage with the garage door open during a bad storm. I decided to stay in the garage and keep working. Big mistake. I never saw what got hit but there was lightening and electrally charged particles crackling and making noises all around the garage, just a foot off the ground, while I was in it. The hair on my head was standing up from it and I could feel the electricity. Being scared didn't begin to describe my feeling at the time.

[Bob Turkovich]

Best personal example of sight vs. sound was watching the Apollo 14 launch. The sound was accompanied by heat pulses from the engines and shock waves on the palm trees.

[Ken Fitzgerald]

I once saw the results of lightning striking the ground directly above a nitrogen charged cable run along side a runway at NAS Meridian, MS. The lighting ran into the the GCA radar (ground controlled approach) damaging the radar, melting electrical copper electrical connectors as big as my thumb and damaged the emergency generator that was supposed to automatically pickup the electrical load. We were several weeks getting that radar and generator back on line. The base has 3 runways. Luckily there was another radar on one of the other two runways that could be used.

Lightning can be impressive and so can the resultant damage!

[Kev Williams]

Since we're telling lightning stories :D -

I met my wife at a private club on a Saturday, it was Aug 3rd; she needed a break from her kids and ex so she got a babysitter and went to have a drink. My birthday was a few days earlier, and a friend living with me was the 'chef' at the club. He offered me a free dinner and some drinks and I had nothing better to do... She was sitting at the bar and spied me while I was throwing darts, asked a waitress about me, she introduced herself, we drank and danced a bit, exchanged phone numbers and went our separate ways. The next day I called only to get 'this number is out of service'. Oh well...

The next Saturday I'd just got home from picking up my kids, and the weather was pretty foul. The phone rang. It was her! She asked why I didn't call? --Anyway, one of us made a mistake with her phone number. About 10 minutes into our chat, no warning,
BOOM!!!
HOLY CRAP!!

I was standing in the doorway between the kitchen and dining area, looking into the kitchen. I turned around--The florescent dining room lights that were turned off, were now lit-- My entire stereo system that was off, every light was on, and BRIGHT- My son was hollering "WOW, it was like a laser light show in here!" -My daughter was scratching her arms, "my arms hurt dad!" , her arms were warm and red... a few seconds after the boom the florescents went dark, and the stereo lights dimmed down to their normal brightness. My pre-amp's time-delay circuit card ended up being blown, and the on/off switch never worked again, at least it was "on". Nothing else was affected. I never did find where the bolt actually hit. All while I'm on a cordless phone with an metal antenna--

That was August 10th. On September 19th, we got married. This September we celebrate our 30th anniversary :)

--That's one...

[Jerome Stanek]

When I was a kid Lightning would strike our chimney about once a year one time I had just walked out the door when it hit I about had a heart attack. The chimney was a steel cylinder 4 ft diameter and 70 ft tall and had 4 steel cables to stabilize it.

[Andrew Seemann]

25 years ago I had a very small bolt hit a utility pole about 20 feet away from where I was standing. Between the bolt and the plasma balls on the wire, it looked like the most cheesy, low budget special effects you have ever seen. I would have laughed if I wasn't speechless and completely terrified.

[Lee DeRaud]

Wait...your cat waits for the thunder to react?!?

Mine levitates about four feet straight up from the initial flash: the "boom" is just her signal to shift gears.

[Steve Demuth]

It was a joke about a cat not a question of scientific inquiry............:D:D:D

Sure, but I'm not a cat. I have a pretty odd sense of humor, and view just about everything as an excuse for a scientific or intellectual inquiry.