Counting seconds to the thunder after seeing lightning to predict how many miles it's away?

Question

My mother has told me ALWAYS, "Now, when you see a bolt of lightning, you can count seconds and how many seconds you've counted until you hear the thunder, that's how many miles away the storm is!"

Is this even accurate, or just an old wives tale?

Answer 1

I've always heard that if you count between the bolt and the clap of thunder you divide the number by 5 and that's approx. the mileage away.  If you got to 16, then the storm is 3 miles away.

Answer 2

It is an estimation.... only!!!

Answer 3

Per the experts, and I am one by the way, ha ha

no, really they say,  for every 5 seconds is 1 mile.'

'

so if you get to 2-3 then run, the lighting is too close to you.

run Forest run, the lighting is too close, run.....

Answer 4

its true but not accurate. for every five seconds between lightning and thunder=one mile away.

Answer 5

Your Mom is right, but I'm guessing she's not a physicist.

The light from the lightning bolt travles at 186,000mph (more or less). That's about as close to "simultaneous" as physics allows.

The sound however only travels at about 770 mph. (more or less, depending on air density, humidity, etc.)

That works out to 343 meters per sec, 1235 km/h, or 770 mph, or 1129 ft/s.

There are 5280 feet in a mile, so 1129 is just a hair over 1/5 of a mile.  (0.21382575 if you want to be sticky about it).

So...if the sound travels 1/5 of a mile per second, then you count the seconds between the flash and the bang, divide by 5 and you get how many miles away it is...more or less.

So yes, your Mom is right...but she forgot to divide by 5.