PFE031: Thunderstorms

Thunderstorms are awesome am I right?

Lightning! Thunder! Rain [sometimes]! Pretty. Loud. Pretty LOUD!

So why am I looking to muck pretty awesome things up with numbers? Because, I don't know, it's you who's reading this, it's probably more of your fault anyways [see above image].

Right, so we're going to review a common and fairly well known trick: the five second rule.

Not that one, the one about lightning and thunder.

Lightning and thunder happen at basically the same time... at the location of the lightning. So if you get hit by lightning you'll see the flash and hear the thunder at the same time [or you won't because your brain will be rather well-done, I don't know]. But as you move away from the lightning [generally a good idea] everyone knows that the thunder slides away from the lightning too... in time. That is, you see a flash and then... BOOM.

Let's science this up now. Light goes fast. I mean, really fast. Count one second: "one one thousand". Light from the earth is basically to the moon in that time. So we can pretend that light's instantaneous for any distances on earth that we are ever going to care about.

Sound, on the other hand, is comparatively pokey. Since sound travels through something [air in this case] it is a little bit dependent on the properties of that material, but at 50F [a reasonable temperature for a thunderstorm I figured] sound travels at about 1107 feet per second. How fast is that? Well, let's see, it's certainly faster than I can run [thank goodness! Otherwise there would be sonic booms all the time]. If we then convert that into seconds per miles [which might seem like a weird unit unless you're a runner] we get about 4.77 seconds per mile - it takes sound just under five seconds to travel a mile.

BUT WAIT! THERE'S MORE!

So apparently sound travels faster when there's more humidity in the air. This is actually a little bit complicated, but a simple model gives about a half a percent increase. This brings our timing down to an even shorter 4.75 seconds per mile. Whatever.

This gives us our standard five second rule [unlike the food one above, this one is rooted in SCIENCE, YEAAA!!!]. Start counting time as soon as you see lightning and stop as soon as you hear the corresponding thunder [if the storm is too active it can be tough to tell which boom corresponds with which flash - you're on your own in these cases]. Take the number of seconds and divide by five [then round up a teensy bit if you want to be more accurate] and that will tell you how far away the lightning is. If you counted 8 seconds you're looking at ~1.6 miles away. Is it just that easy? It's just that easy.

But... who cares how far away it is? What we really care about is

Shh. I'm counting between the lightning and the thunder to see if the storm is coming or going.

whether the storm is coming, leaving, or passing us by. If we repeat the above process, we can get the distance to the strongest part of the storm over a period of time. If the distances are shrinking head for cover. Of course, you can also probably tell if the lightning is getting brighter and the thunder is getting louder and if it starts pouring on your poor unprotected head - but this way is way more fun.

That's thunderstorms.